Serpentinite stories – Beverly Creek to Ingalls Lake

So I dropped a lot of hints in my post about my Lake Ingalls hiking adventure about how I made incorrect assumptions about the rock. Every geologist is biased by the rocks they studied first. For me, I’m biased by the brown and orange sandstones of the Tennessee’s and Kentucky’s Cumberland Plateau. Ergo orange rock = sandstone. When I dragged my butt over Turnpike pass and saw the undulating orange cliffs with blocky fractures, my mind immediately went back to the Red River Gorge in Kentucky. “Sandstone! We’re finally back on familiar ground!”

(orange slopes to the left, granite (or is it?) peaks to the right. Seen from “Valley View” on the next map)

Well I was faked out. Not only was I on unfamiliar ground, I was on unfamiliar oceanic crust. It turns out that central Washington is part of the same accreted terrane story that I’ve investigated in Oregon and in the San Juan Islands. If you need background on accreted terranes before I dive into the world of the oceanic crust and why it’s hanging out at 6,00 feet, check out my blog post Accreted terranes: a slow-motion pileup on the Pacific Coast.

The vast majority of Washington’s foundation – all of it except for a sliver by Idaho – never belonged to the ancient North American craton to begin with. The breakup of Pangaea 200 million years ago activated a subduction zone here that gobbled up oceanic crust as North America crept westward. Bits of island arcs and seamounts were plastered to North America like icing around the mouth of a carefree toddler eating her birthday cake, as the dense ocean crust subducted below the lighter continent. But sometimes chunks of the oceanic crust itself would snap off of the subducting plate with the inexorable force of the collision. These piece of ocean crust beached on the continent are called ophiolites. Sometimes rocks from even deeper in the earth break free with the ophiolite – “ultra-mafic” rocks from the mantle, which underlies both the oceanic and continental crusts. As these almost- subducted rocks rise to the surface they absorb water from overlying rocks and change their mineral structure dramatically.

Oceanic crust sinks because its minerals contain more heavy elements than the minerals that make up the rocks of the continental crust. These minerals include magnesium and iron, whose names combine to form “mafic”, the common term that describes oceanic crustal rocks. “Ma” from magnesium, “f” from Fe, iron’s abbreviation, and an “ic” on the end to give the word the ability to impersonate an adjective. Mafic rocks are exclusively igneous in origin. Whether the mafic magma cools deep within the crust or erupt on the seafloor, they cool in environments low in oxygen. It comes as a rude shock to their chemistry then, when they’re doused in water and scraped onto the continent. The greenish black minerals containing ferric iron oxidizes to rusty ferrous iron as the rocks are exposed to air.

Which brings me to my point. These orange rocks? They’re actually green inside.

Here’s the TL:DR on the rocks I met on the way to Lake Ingalls, with gratuitous details below the map.

  1. My hike started in sandstone deposited in a river delta tens of millions of years ago.
  2. I started to get out of breath as I hiked onto the quaternary alluvial deposits – landslides from the tall peaks above my head.
  3. Those peaks are made of Lake Ingalls serpentinite – metamorphosed chunks of the mantle three times as old as the sandstone.
  4. After lunch I hiked up into Lake Ingalls diabase and gabbro at Turnpike Pass – ocean crust rocks that have the same composition as basalt but cooled without erupting.
  5. I climbed back down into more landslide and stream deposits before crossing the landscape’s youngest sediment at the base of Turnpike Valley – glacial till deposited only 15,000 years ago. A baby!
  6. After another jaunt along the stream deposits, I reached the campsite built on more serpentinite. So many black-speckled boulders from the Mt. Stuart granodiorite had tumbled down here that the serpentinite is barely perceivable. The granodiorite is only twice as old as the sandstone at the trailhead.
  7. The next day, I hiked on more serpentinite all the way to Lake Ingalls.

If you’re on a phone or small, you’ll definitely want to open this image and zoom around. The map below outlines these rocks I met in a visual form, and the the next image introduces you to the geology of the view of Mt. Stuart from the approach to Lake Ingalls.

Rock types looking northeast towards Mt. Stuart from the approach to Lake Ingalls from Ingalls Creek, along the Ingalls Way Trail. I have to admit I don’t care too much to distinguish the tonalite, quartz diorite, and granodiorite – they all tell the same story of an invading plume of magma 92 million years ago. You can really tell how resistant that rock is is by the steep cliffs of Mt. Stuart compared to the sloping domes of serpentinite by Lake Ingalls!

Congratulations, you made it past the map! Time to translate what I learned from the Wenatchee Quadrangle USGS bulletin out of hyper-jargon into only moderate jargon and learn what stories these rocks tell.

Swauk Formation (Ec(1s)): Between 54 and 42 millions years old. This formation is a sandstone made of approximately 35-40% quartz grains, 15-20% fragments of rock, and 65% eroded rock of volcanic origin. It was cemented into rock by felspar and carbonate minerals. This unit is made up of material that was eroded from the Mt. Stuart Batholith, Ingalls Tectonic Complex, and other local metamorphic rocks of the Easton unit that I’m not going into in this post. Streams and rivers deposited this material in a low-lying regional basin which was later split by the Straight Creek Fault. Related rocks can be found as far north as Bellingham, where they are called the Chuckanut formation. The section of the Swauk formation that I hiked through was heavily forested and I didn’t meet any good outcrops.

Ingalls Tectonic Complex – Jurassic intrusive basic (mafic) rocks – Jib(i): ~140 million years old. A unit of the Ingalls Tectonic Complex that is made of predominantly diabase and pyroxene gabbro, with anorthite and weakly foliated amphibolite. Diabase and gabbro the same mineral composition as basalt, but unlike basalt which is cooled lava (erupted onto the seafloor), diabase and gabbro are cooled magma (cooled within the oceanic plate without erupting). Diabase cooled quickly and has very small grains that are barely visible to the naked eye, while gabbro cooled more slowly and so is made of larger mineral crystals. Anorthite is a rare kind of white feldspar mineral common in mafic (ocean crust) igneous rocks. The white rocks I encountered at the top of Beverly Creek were anorthite, and the shiny green rocks that distracted me were amphibolite. “Weakly foliated” means that the rock was under enough pressure to realign the mineral grains perpendicular to the direction of force, but only to a minor degree.

Left hand side of image – dark green amphibolite. Right hand side – white anorthosite.

Jurassic Ingalls Serpentinite and Peridotite (Ju(i)): ~140 million years old. A unit of the Ingalls Tectonic Complex made of foliated and massive serpentinite, serpentinized peridotite, and metamorphosed versions of these two rocks call metaserpentite and metaperidotite. Serpentinite and its associated process “serpentinization” are named after the root word for “snake”, as the process transforms the original rocks with a green color and often a slick scaly texture. This happens when minerals rich in iron and magnesium that are abundant in rocks from the oceanic plate, such as olivine, chromite, and pyroxene are forced to absorb large amounts of water during subduction. This hydration causes the rock to swell 30% to 40% from its original size and releases large amounts of heat – enough to raise the temperature of the rock by up to 500 degrees F. This increase in volume makes the rock less dense and more likely to slowly bob to the surface of the subduction zone.

When we see serpentinized rock at the surface, it means that a chunk of the ocean crust was partially subducted but somehow was spat back up to the surface where it ended up beached on the continental crust. Metaserpentinite and metaperidotite occur when that rock stayed within the subduction zone for a longer amount of time and was metamorphosed by heat and pressure as well as chemically metamorphosed by serpentinization. In the wild, this rock unit presents as strong outcrops with a blocky shape that have been weathered to an orangish tan color as the high iron content of the rock reacts to precipitation and oxidizes into rust. If a curious geologist were to take a hammer to these rocks, the insides would be light to moderately dark green. Around Lake Ingalls, fresh exposures of this unit are light brownish green with dark speckles of the mineral chromite.

Fun fact – the minerals in serpentinite, most notably chromium and magnesium, are significantly poisonous to vegetation, and it is the reason that serpentinite landscapes are most often barren of trees or only inhabited by scraggly struggling trees.

Foreground – a piece of lightly weathered serpentinite with distinctive green-black chromite crystals. Green faces of freshly exposed serpentinite are visible directly above the central rock sample, on the far left side of the image, and in the top left corner. General background – weathered orange outside of serpentinite near Lake Ingalls.

The two photos above shows two small scale features in the serpentinite – pressure fractures with remineralization, and also a close-up of the rock as it weathers. The right-hand photo shows just how orange the chromite crystal are, compared with how black/dark green they look in the fresh face of the first photo. The paler mineralization in the cracks is very brittle and broke off in my hand. Talc and tremolite are associated with hydrothermal deposition in serpentinite, so I think they’re the primary suspects.

Mount Stuart Intrusive Rocks : 96 to 91 million years old. This formation is also referred to as the Mount Stuart Batholith, referring to its shape (giant blob) and manner of emplacement (cooled underground). Diorite and granodiorite with medium-sized grains. This rock is predominantly made of the mineral plagioclase feldspar, with minor quartz (pale gray crystals), biotite (dark crystals that flash in the sunlight), and amphibole (dark greenish black crystals). The rising plume of magma that would become the Mount Stuart Batholith punched its way through the Ingalls Tectonic Complex and contains small pieces of that formation that it gobbled up on the way. In some areas near the Mt. Stuart batholith, the heat of the intruding granodiorite literally cooked the surrounding serpentinite minerals into the soft blue-gray mineral called talc. This very durable rock forms the setting for the Enchantments and also for the Thunder Mountain Lakes which I’ve written about previously. On this map, it is separated into three concentric zones of felsic (continent-derived) intrusive rock with slightly different mineral content.

  • Kit(sc) – Cretaceous intrusive tonalite – >20% quartz, significant plagioclase feldspar, some amphibole and biotite. Mostly pale, more gray than white, scattered dark speckles. Occurs around the southern and western edges of the batholith.
  • Kiq(s) – Cretaceous intrusive quartz diorite – 5% to 20% quartz, significant plagioclase feldspar, some amphibole and biotite. Mostly pale, whitish, scattered dark speckles. Makes up the bulk of Mt. Stuart, with the exception of the top hundred feet, as well as much of the Enchantments.
  • Kigd(s) – Cretaceous intrusive granodiorite – >20% quartz, both plagioclase and potassium feldspar, ~ 25% amphibole and biotite. Mostly pale, with gray quartz, white plagioclase feldspar, and pinkish potassium feldspar crystals as well as around 25% dark crystals of amphibole and biotite. Occurs in the center of the batholith, where it makes up the summit of Mt. Stuart and the southern bulwark of the Enchantments including Little Annapurna.
My little knitted “alien” friends perched on a stack of tonalite and quartz diorite rocks forming a cairn, with the huge quartz diorite cliffs of Mt. Stuart in the background.

Quaternary Lakedale Hyak Till (Qlht): ~15,000 years old. What a cute little geologic baby, someday it will get buried properly and become real rock. This unconsolidated sediment was deposited by glaciers during the Pleistocene era. It’s jumbled mixture of all kinds of sediment grain sizes from clay to boulders that the glacier scraped off the rock and deposit as it moved. I passed this unit on the southern side of the junctions of Turnpike Creek and Fourth Creek with Ingalls Creek.

Time to zoom out onto the big map! Let’s put all these rocks into order based on their history – oldest on the bottom of the legend. Lake Ingalls is a little light blue dot just left of and below center on this map.

Even the oldest unit on this map is still only 4.5% the age of the earth. Deep geologic time messes with my mind. But more obviously, the representation of geologic time looks like a MS Paint scribble doodle. Talking about MS Paint, I drew an extremely rough cross section from north to south through the map to give the scribbles some 3D context.

I’m not going to get into the whole story of the many, many terranes that built this area in this particular blog post. I will defer to Professor Nick Zentner (Exotic P – Easton & Ingalls video) if you want to learn more about this phenomenon as it pertains to Central Washington, as I would only be (at best) giving a Spark Notes of one of his lectures. But the order of events in this region is thus:

  1. The Easton terrane containing the Chiwaukum Schist docks onto the North American Craton. Schist is a metamorphic rock made of sedimentary rocks that were subjected to intense heat and pressure until their mineral grains stretched and warped into new shapes.
  2. The Lake Ingalls Ophiolite docks onto North America, and,
  3. the Windy Pass Thrust Fault carries it over the Chiwaukum Schist,
  4. The Mt. Stuart Batholith punches through both the Easton and Lake Ingalls terranes,
  5. The sandstones of the Swauk formation are formed from sediment eroding off of all of the above rocks.

Thanks for reading my post, and I hope you can eventually hike out here too! I didn’t take as many photos as I should have on this hike. If I make it out here again next summer I will add a follow up to this post.

And don’t forget to pay toll to the douglas fir squirrels on the way out 🙂



Ireland: Rocks of Newgrange

This post is the last in a series that covers last summer’s van Stolk family trip to Ireland. Here’s the highlight map to get you oriented:



We don’t know much about the people who built the massive passage tomb at Newgrange over 5,000 years ago. They left no written record, and we can only guess at how they used the ritual passages aligned precisely to the winter solstice. However one thing is obvious – they had a particular eye for beauty and detail.

How do we know this? The story is all in the rocks. Black and white, rough and smooth, plain and intricately carved. The massive “kerb stones” along the bottom of the monument were not shaped by human tools except for detailed swirling patterns created with small chisels. The builders must have scavenged all over the countryside for boulders of the appropriate size to decorate. And many of the rocks come from dozens of miles away!


Swirling patterns on a kerb stone

Bright white quartz cobbles from the Wicklow Mountains (near Glendalough, which I wrote about in the last post), dark speckled granodiorite cobbles from the Mourne Mountains, and dark gabbro cobbles from the Cooley Mountains form designs on the outer walls of the monument. Smooth greywacke from Clogherhead in County Louth forms the inner passageway and outer kerb stones. Finally, the interior of the huge mound was built up from local gravel from the banks of the Boyne River.


Keep in mind, Newgrange was built before the invention of the wheel made it to Ireland. Archaeologists think that the rocks were carried as far as possible by boat before being loaded onto log rollers or sledges to get to their final destination.The 97 kerb stones each weigh at least a ton, and it’s estimated that Newgrange contains 200,000 tons of stone. These ancient people committed themselves to a serious labor of love!

Archaeologists debate the period of time that people used Newgrange as a spiritual and cultural site. However they agree that it was “lost” around the 5th century and then rediscovered at the turn of the 18th century when a local landowner went looking for stones to expand his buildings. Amateur “antiquarians” from around the British Isles visited the site from its rediscovery in 1699 to the 1920s. A formal archaeological survey started in 1962 and was complete in 1973. During this process, the tomb was “restored” to the way that we see it today by educated (and controversial) guesswork. The researchers found the cobbles piled down by the base of the mound and posited that they had originally been pressed into the side of the mound as a kind of retaining wall.

newgrange rock types

So who make sup this cast of characters? Distances measured in ArcMap, from a generalized geologic unit to Newgrange assuming that the builders used boats as much as possible to transport the rocks.

Quartz: Distance traveled: about 65 miles. These are the same quartz veins that I wrote about in my Glendalough post!

Gabbro: Distance traveled: about 35 miles. This is a dark coarse-grained intrusive igneous rock.  It’s the most plentiful rock in the ocean’s crust, and when found on land is associated with rift zones where continents have torn apart from each other. It has the same mineral composition as basalt (like at Giant’s Causeway) but cooled slowly underground instead of solidifying quickly above the surface. It’s mostly made of the black mineral pyroxene, with smaller amounts of white plagioclase feldspar and green olivine. This gabbro even shares the same age and source as the Giant’s Causeway – about 60 million years old, and formed when Pangaea ripped apart to form the modern Atlantic Ocean.

Granodiorite: Distance traveled: about 40 miles. This rock is very much like granite but has a different balance of the two feldspar minerals. It has more plagioclase feldspar that granite does, and so appears whiter. This contrasts strikingly with the black amphibole and pyroxene minerals in the rock, so granodiorite puts me in mind of a dalmatian’s color scheme. The other kind of feldspar, orthoclase, can add a pinker tinge to granite. The Newry Granodiorite complex crystallized in the Caledonian period – about 400 million years ago – as a byproduct of the closure  of the ancient Iapetus Sea.

Graywacke: Distance traveled: about 15 miles. This particular kind of sandstone forms in deep marine environments when undersea avalanches, called turbidity currents,  mix up all sizes of particles – silt, clay, sand, and gravel. This rock was formed during the Silurian period between 433 and 419 million years ago, and got shuffled to the surface since then.

I can only wonder what these rocks meant to Newgrange’s builders. Some thoughtful ancient travelers noted their favorite rocks around the island, and decided that they ought to be a part of their community’s treasure. I think we might have gotten along.


Granodiorite at the Mourne Mountains:

Gabbro on the Cooley Peninsula:


Ireland: The Giant’s Causeway and Carrick-A-Rede

There are some geologic features that are just way too cool for humans NOT to write a myth about them. The long-standing explanation of the columns of the Giants Causeway was that the giant Finn MacCool wanted to build a bridge to attack his rival in Scotland and that they destroyed the bridge in their fighting, leaving only the Causeway in Ireland and Fingal’s Cave in Scotland remaining. Then that long-standing story gets to rub shoulders with whatever geologic explanation comes along a few centuries later.

On this vacation, we got to road-trip to one of the most stunning geologic sites in Ireland – the Giant’s Causeway.  While we were up there anyways we decided to check out the Carrick-A-Rede rope bridge too, where I got an unexpected extra dose of cool geology.

Ireland trip

Giant’s Causeway is a phenomenal exposure of basalt. Sure, the rock type itself is nothing new. I wrote my thesis about basalt in northeastern Oregon. This particular basalt became famous for the huge field of well-exposed basalt columns, a feature that forms when lava gets the chance to cool slowly. And not only do you get to see the sides of the columns like you can in Oregon, but you can clamber over the tops of them too. It’s well worth the money for the audio tour. There are two versions for two different audiences- normal person and geology nerd – and both are entertaining and informative.


This basalt flowed out of cracks in the local limestone around 55 to 60 million years ago, when the Atlantic Ocean was opening up. It took two stages to create the landscape here. First, about 6 basalt flows spread evenly across the landscape. Then volcanism stopped for a while; there was enough time for a the top part of the basalt to be weathered a rusty brown color as chemical reaction changed the basalt to laterite, lithomarge and bauxite. This zone is called the Interbasaltic Formation here. There was also time for water to carve a valley into the landscape. Later, volcanism restarted and a huge volume of lava poured into the river valley! At the time of formation, this deposit would have been a lava lake 90 meters (295 feet) deep! We know it had to have happened all in one event, because there are no weathered layers within it.You can see a basalt cliff at the level of my head in the background of the photo to my right – that basalt was deposited on top of the plateau beside the river valley. The thickness of the lava in the river valley meant that it cooled quite slowly, allowing the formation of the regular 4 to 7 sided columns.

You can see what I just described in the photo below. Note that you can see all three layers behind my mom, but that she’s standing on the Giant’s Causeway basalt that flowed into the valley that was cut into the Lower Basalt Group.

Giant's Causeway basalt annotated photo

My mom Lise, always the best tour guide, is here to introduce you to basalt geology! We didn’t hike up to the Organ Pipes, but they’re a beautiful exposure of both the colonnade and entablature layers of the Giant’s Causeway Basalt formation. Finn MacCool’s Chimneys are precarious free-standing basalt columns whose companions were eroded away on the headland.


Checking out the lower basalt groups – they were physically weathered into rounded shapes as groundwater percolated down into the formation. The fancy name for this is “spheroidal weathering”. You can see a little bit of the Interbasaltic group in the top left corner of the photo, where the dark gray basalt has been chemically weathered into orange/brown minerals.

Whether they’re the ones I studied in Oregon or the Irish ones in this post, basalt flows have a certain internal structure to them. It’s determined by the fact that the molten rock cools mostly from the top down, with a little bit of cooling driven by the cooler ground underneath the flow. The quicker a region of the lava cools, the smaller the size of the cooling features. Air or contact with underlying rock rapidly cooled the lava at the very top or bottom of the flow, giving it a crumbly texture. In the diagram below, these areas are the vesicular top and bottom. Just below the vesicular top, the rock was cooling more slowly. Small cracks propagated from the top of the flow downwards as the rock cooled and shrank. The rock was cooling just quickly enough that the pattern of cracks was somewhat chaotic, creating blocky shapes or the curved and twisting “fanning columns” in this “entablature” zone.

basalt flow interior

Illustration of a basalt flow interior with vesicular zones, entablature, and colonnade from:

At Giant’s Causeway you can see huge boulders from the entablature zone that have fallen down among the columns. They have kind of a “giant meatball” rubbly texture that contrasts with the smooth elegance of the columns but makes them easy to climb.


Below that is the sweet spot of cooling, whose features dominate the Giant’s Causeway. In the “colonnade” zone of the basalt flow the cracking pattern propagates neatly downwards. A hexagonal pattern develops when cooling contraction occurs at centers of mass that are evenly spaced in a homogeneous body of lava. If there are variations in the thickness or composition of the lava then other geometries of fracture may occur, with anywhere from 4 to 8 sides.


Giant’s Causeway’s famous colonnade layer, with geologist for scale.

You can see in the picture above that the columns are broken by joints perpendicular to the ones that define the columns. These are subtle ball-and-socket joints that formed when the area was subjected to horizontal stresses after the rock had cooled and the columns had formed. These ball-and-sockets allow the formation to bend a bit.


concave “socket” column top on the left, convex “ball” column top on the upper right.

Later that day the sun came out and we decided to check out the Carrick-A-Rede rope bridge. It’s absolutely touristy but worth it on a beautiful day like that. The bridge and island are only accessible by paying for a group tour that departs at regular intervals. You end up parking in a nearby abandoned limestone quarry called Larrybane Quarry.  It has beautiful seaside views, and a fight scene from Game of Thrones was filmed here.


Unfenced drops? Cliff edges? Count me in. Spoiler alert, our mom did not keep us close…

How can you ask a geologist to stay on the path when there are cool chert nodules to investigate in sea caves? In the right-hand photo, the black rock is chert. In the photo with my sister and me in it on the left, you can see how these chert nodules are distributed in horizontal bands in the limestone. These nodules are formed after the remains of microscopic organisms like coccolithophores, radiolarians, and diatoms are laid down and start to solidify into rock. Water in the formation dissolves some of the silica-rich remains and redeposits them in layers around impurities in the sediment, forming blobs of chert that are often called “flint” when they’re found in chalk beds like these.

In the top right corner of the photo you can see stalactites – this is the only known location in the Ulster Limestone (a.k.a. Upper Cretaceous Limestone) along the Causeway Coast with these distinctive formations.


When the line of tourists waiting to get across the bridge is longer than the bridge, it might be a tourist trap.

This was just a detour to the main attraction – the Carrick-A-Rede rope bridge. It was constructed in 1755 to allow fishermen access to fruitful salmon fishing groups, and has been developed as a somewhat oversold tourist attraction. It has a neat geologic history though. The little island stands tall because it’s the eroded neck of a volcano! It formed 62 million years ago, just a little bit before the basalt at the Giant’s Causeway. The island is formed of dolerite, a kind of intrusive volcanic rock. When you’re on the island and looking back to the mainland, you can see large blocks of basalt and limestone suspended in a matrix of volcanic ash.



The short hike to the bridge takes you down rocky staircase and along gravel paths with lovely views out to sea. The tour guides don’t encourage the group to spend too much time on the island itself, but we got to take twenty minutes or so to spy on the seagull nests, eat some snacks, and admire the view out to Rathlin Island.


Here’s a map of an overview of the geology around Giant’s Causeway and Carrick-a-Rede that I put together in ArcMap. This is from the 1:500,000km shapefile available from the Geological Survey of Ireland. The more detailed 1:100,00K map excludes Northern Ireland… I guess political animosity somehow spilled over into data collection and sharing here. That’s a shame. So Carrick-A-Rede itself isn’t mapped here.

Northern Ireland Geology

Stay tuned for a geology/archaeology crossover event! My family headed to the Newgrange Stone Age Passage Tomb later that week.


booklet on the geology of Northern Ireland’s Coast:

A field trip at the Sand Atlas blog whose author took some better photos of the formations:

Debbie Hanneman over at GeoPostings did this trip back in 2017 and shared some great photos:

AGU resource on columnar jointing:

Information about the geology at Carrick-A-Rede:

Article about the formation of chert nodules in carbonate beds:

Maliva, Robert G., and Raymond Siever. “Nodular Chert Formation in Carbonate Rocks.” The Journal of Geology, vol. 97, no. 4, 1989, pp. 421–433. JSTOR, Accessed 14 May 2020.

Cool podcast about the tiny creatures that become chalk, courtesy of Radiolab:

Ireland: Mining’s legacy in Glendalough

After Heather and I explored Brittany we headed north to join 35 other van Stolks and their partners in Ireland for a family reunion. No, we aren’t Irish, but the Dutch family wanted to vacation outside of the Netherlands and the American part of the family wanted to spend time in a scenic part of northern Europe. Ireland was a delightful compromise. We converged on a holiday cottage complex just north of Dublin where we spent a convivial time moving from porch to porch catching up on years of news. The whole bunch of us set out in a rather unruly convoy to highlights like Newgrange, Slane Castle, and a sheep herding demonstration further afield in Glendalough.

Ireland trip

Glendalough is a jewel of a lake in the mountains south of Dublin in County Wicklow, a rugged contrast to the gently rolling green hills usually associated with Ireland. We all oohed and aahed at the sheepdogs and their  puppies, and then a smaller group of cousins set out on a hike to work off the cabin fever.We did the “white trail” around the upper and lower lakes at Glendalough. It’s a stunning 7.8 mile loop! We did it counter-clockwise, which results in a gentler upward climb. If you hike this clockwise you have to climb up the hundreds of wooden stairs on the eastern side of the lake… not my idea of a great time. Going counter-clockwise also results in beautiful views of the monastery site from the top of the cliff!

Glendalough white trail

Trail map from

It turned out to be a lesson in the importance of looking at the scale of the contour lines on the topographic map at the visitor’s center. We thought “oh, we only cross one topo line on the map, the trail must stay close to the lake.” Well it turned out that the distance between topo lines on that map was 0.4 kilometers – about 1,500 feet. My cousins with a strong aversion to heights were absolute troopers. The views from the top were amazing!


Hanging out in a textbook-perfect glacial valley, with the old mine buildings in the background. Halfway to the top!


At the top! Two cousins aren’t in this picture because they didn’t fancy spending more time at the top of this cliff than absolutely necessary and they also are much fitter than the rest of us.


The southern cliff is topped with blanket bogs. They’re an extremely soggy and sensitive landscape, so the park put in a couple miles of boardwalk to minimize human impact. I felt like I was somewhere in Tolkien’s Middle Earth!

Glendalough seems like a valley outside time, once you step away from the tourist shops. The paths take you by an old monastery, streams in strange mossy landscapes, and the lake itself surround by hills and forests. It came as a surprise to me when we found the remnants of an abandoned mine at the eastern end of the lake.


It turns out that between the 1790s and the 1920s this area a hive of mining activity. You can easily tell what the miners were looking for in the landscape – the scars of white quartz rubble are the giveaway (see the slope on the right side of the photo above). The miners were looking for lead, silver, and zinc. Specifically, they found it in the minerals galena and sphalerite.

Image of galena (dark gray) and sphalerite (orange-ish brown) in quartz (white) from the Glendalough mine from the National Museum of Ireland.

Galena is a mineral composed of equal amounts of lead and sulphur (its formula is PbS). In this area silver substitutes for lead in the crystal structure around 5% of the time, making it a valuable ore for silver as well as lead. Sphalerite is made of equal amounts of zinc and sulphur (formula is ZnS). But how did they get here, and why are they only found in the quartz?

Let’s take a step back an look at the history of the local landscape over the past few million years, courtesy of an interpretive sign at Glendalough’s ranger center. The information is great so I didn’t bother re-typing it, but you may have to click on the image and zoom to read it if you’re reading this on your phone.


Photo of an interpretive sign of Glendalough's geology at the ranger center.

Photo of an interpretive sign of Glendalough’s geology at the ranger center.

Two types of rocks form the foundation of this landscape: a metamorphosed version of mudstone or shale called schist, and the granite which muscled its way up into those rocks during the Caledonian orogeny. Remember that from a few blog posts back? This Irish granite is a cousin of sorts to the granite that became the Mont Saint Michel. It too was formed as the heat created by the collision of Laurentia, Baltica, and Avalonia created magma that rose up into overlying rocks and cooled into huge lumps of granite (called batholiths in geologist jargon). In the map below, the granite is shown in red. It also shows just how many mines were once active in this area!

Glendalough mining

A map of mining activities near Glendalough – we hiked past #7 and #8, Glendalough Valley mine and Van Diemen’s land mine. This map also shows the geologic contrast in the region between the schist (light pink) to the east and the granite (red) to the west of the lake. This map is from

This particular batholith is called the Leinster Granite batholith and underlies much of County Wicklow. It’s harder than the surrounding schist and creates more rugged cliffs when assaulted with millions of years of wind, rain, and glaciers. In the Wicklow mountains the granite slopes tend to be covered in boulder fields, and the schist slopes are covered in heather and other creeping low bushes. Neither type of rock weathers into particularly inviting soil for plants, at least not in the geologically short period since the last Ice Age.

Rock specimens that I couldn’t resist at Glendalough: Schist with neat protruding flexible sheet of mica (left), granite (center), bits of waste quartz from the mining operation (right)

Here’s a map of the mine site that is #7 on the map above, and the first area we came to on our hike. This map was put together by the educational group “Glens of Lead”. This group put up some great historical signs in along the park about how the old mining operations worked.


And here’s a map of the second area on the hike, #8 on the map.


Very little of the original infrastructure remains today, except for the stone buildings at the Glendalough mine site and the bright white quartz of the tailings rubble from the mines. The shafts and tunnels have been blocked off and the old tramways completely dismantled. The site seems very wild again.


Standing on the schist side of the valley, looking over to the steep granite cliffs and the piles of quartz tailings below the exits of the old mine shafts 1,000 feet below.

Above right: granite with vein of hydrothermal mineralization (foot for scale) in the mining area, compared with schist exposed at the top of the cliff on the south side of the lake.

But how does lead ore get into quartz veins? I’ve written about continental collisions and granite before in this blog, but not really about smaller processes of metamorphism. It’s time to fire up MS Paint again.


Magma bodies (red) rise off of the subducting oceanic crust and cool into intrusive igneous rocks (pink). Water (blue speckles) in the oceanic crust allows the crust to melt at lower temperatures than the surrounding rock, and travels upwards as a part of the magma. Diagram by C. van Stolk.

Back around 300 million years ago, the ocean Iapetus was closing as the old continents Laurentia, Gondwana, and Avalonia moved towards each other. The oceanic crust under Iapetus had to go somewhere; it subducted under the continents. After a few million years of being underwater that oceanic crust was pretty soggy as rocks go. The conveyor belt of plate tectonics drove the heavy oceanic crust down under the lighter continental crust.  It began to melt as it sank beneath the continent and into the upper layer of Earth’s mantle called the asthenosphere.

It turns out that this water trapped in the crust is kind of the “secret sauce” of metamorphism. The presence of water allows rocks to melt at lower temperatures than they would otherwise. Metamorphism boils down to two variables – heat and pressure. Both increase vertically with depth in the earth’s crust. Pressure also increases horizontally in collision zones. In the presence of equal amounts of heat and pressure, wet rock will melt to a greater degree than dry rock.

Anyone who has taken a ride in a hot air balloon learns that heat rises – the hot air in the balloon keeps the passengers aloft in the cooler surrounding air. The blobs of magma rising from the subducting wet oceanic crust are much like extremely dense, slow-motion hot air balloons – they rise through any weakness they can find in the surrounding cooler and drier rock. The blobs of magma become batholiths of intrusive rock when they cool, like the granite here. As the granite cooled, the heat had to go somewhere, just as the oceanic plate had to go somewhere as the ocean closed. The magma “cooked” the shales that surrounded it into the metamorphosed version – schist (see purple “contact metamorphism” on the diagram below). However the story of the water that magma contained isn’t over.

subduction with contact metamorphism

If water can’t fit into the crystal structure of the magma as it cools into intrusive igneous rocks, it is released from the melt. It takes along ions that can be dissolved in it and travels into cracks in the surrounding rock. Often these “cracks” are caused by faults or by joints caused by horizontal pressure. One of the most common elements carried along this way is silica, which in combination with oxygen forms quartz veins as it cools. This mineral-rich hot water is called a “hydrothermal solution”.

Image with no description

Diagram of hydrothermal alteration from (a) Shows a magma body that has risen into cooler rock and is “cooking” it shown by the purple aureole. (b) Shows magmatic water being released from the magma body through veins. (c) Shows how groundwater moving past the magma body can also carry dissolved minerals away from it to other locations.

As the hydrothermal solution rises and cools, minerals form out of the solution like rock sugar forming out of hot sugar syrup as it cools down. Not every part of the solution is really well mixed – some parts of the solution are like oil and water and stay somewhat distinct as they travel together. Examples of this are silicate minerals (i.e. quartz SiO2, feldspar KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8) and sulphide minerals (galena PbS, sphalerite ZnS). As the solution cools, these two types of minerals form adjacent but separate structures.

So here at Glendalough, you have granite and schist cut through with veins of hydrothermal rocks that contain chunks of sulphide ore minerals in the more abundant quartz. The miners followed these hydrothermal veins to find the valuable ore, and discarded the attractive but comparably worthless quartz in tailings piles at the site after the rock was put through a huge crusher to break out the softer sulphide ore minerals. I was sorry to notice that they were so thorough that a casual geologist really can’t find any of that ore nowadays.

I was happy enough to take away great memories, beautiful views, and a few new rocks in my pocket.


A good brief history of the mines here:

Brief intro to geology of Glendalough here:

detailed geological survey of mining in the region:

detailed geological survey of mining at Glendalough specifically:

geological map of Ireland:

Maps of lead mining in the area by the local education group “Glens of Lead”:

More about the Iapetus Suture, which connects the half of Ireland/Scotland that was once Laurentia (proto-North America) with the half that was once Avalonia (proto-Europe).

Interesting map of the terranes that make up Ireland:

Ireland through geologic time:

Specimen of galena in quartz from the mine:

More about contact metamorphism/hydrothermal alteration/sulfide ore bodies

Contact metamorphism with good diagrams:

Overview of sulfide ores:

Cliffsnotes version of hydrothermal metamorphism:

Detailed review of ore genesis, including immiscible solutions.

Mazes of mines and catacombs beneath Paris

The SacrĂ©-CĹ“ur Basilica was swarming with tourists on the first day that Elaine, Heather, and I set out to explore it. The line for entry stretched all the way across the plaza and we could hear the muffled din of the crowds within the sanctuary spilling out through the doors. We made a unanimous decision to avoid the chaos by heading to the quieter sanctuary of the nearby MusĂ©e de Monmartre. It’s dedicated to the artists and cabarets that gave the neighborhood its bohemian reputation at the end of the 1800s, and was the last place I though I’d find anything geological. But lo and behold, it had a small exhibit on the gypsum mines that used to be active on the Montmartre Butte, as sketched by the Impressionists.

These mines complicated the construction of the Basilica that we had considered visiting that day. In the 1870s the Parisian government committed to building a huge Catholic monument there as an unmistakable reminder of the power of church and state. Montmartre had been the birthplace of the radical socialist Commune movement that had unsuccessfully tried to overthrow the government in 1871, and the government wanted to remind the neighborhood of who really called the shots. However before the structure could rise above the surface, the foundation required 83 pillars sunk 130 feet deep into the rock layers below the gypsum mines.

I had something of an epiphany (or more accurately, and “oh, duh!” moment) – gypsum is the main ingredient in “Plaster of Paris”! So that’s where it came from! In particular, it came from the green areas on the map below:

Mines of paris translated

Montmartre is clearly visible as the ring-shaped cluster of gypsum mines and the center top of the figure. map translated from French by C. van Stolk. By Plan: Émile GĂ©rards (1859–1920) BnF Notice d’autoritĂ© personneDigital copy: ThePromenader – Own work, Public Domain,


Most of the pale building stone that makes the City of Light so distinctive actually comes from within its limits! It gave me a sense of the huge scale of mining in the city that most of what we see on the surface came from underneath it. The gypsum was mined extensively beginning in the Middle Ages to create fire-resistant covering for wooden structures. You can see the distinctive cream or yellow-ish limestone in almost all of the buildings in Paris built before the 1770s, from the Saint-Germaine church to the grand mansions between the Marais and the Place des Vosges. The limestone is riddled with little cone and spiral shaped fossils too, if you look carefully.

These quarries have been active since the Romans occupied what they called Lutece, but the city didn’t get its wake-up call until 1777 when a gaping sinkhole swallowed an entire city block near what’s now the Place Denfert-Rochereau. That’s when King Louis XVI banned mining within the city limits. He also commissioned Paris’s first mine inspector, Charles-Axel Guillaumot, to map the warren beneath their feet and shore up the weak places to prevent a repeat of the “Place d’Enfer” disaster. M. Guillaumot earned the nickname “the savior of Paris” and was one of the few royal appointees of that era to survive the guillotine – the revolutionaries considered him too useful.

Around the same time, Parisians realized that the former quarries posed a solution to another pressing problem – unmanageable overcrowding at cemeteries above ground. Between 1785 and 1814 the bones of over 6 million people who had died since the founding of the city were disinterred and moved in nocturnal religious processions into the properly sanctified sections of the tunnels designated as the municipal ossuary or catacomb just outside what was then the southern boundary of the city. The catacombs were opened to the general public for tours in 1810.

119 years afterwards, Elaine, Heather, and I set out to wait in the long line to enter the Municipal Ossuary a.k.a. the Catacombs of Paris. It’s a rare attraction that appeals the Elaine’s love of spooky things, my love of rocks, Heather’s interest in history, and all of our pressing interest in getting out of the 97 degree heat. We just managed to get into the last tour group before the gates closed for the day! Because of the time crunch we had to fly through the geology exhibition in favor of getting to the creepy bits but I took photos of the placards, some of which I have translated below. For photos of the ensuing Super Spooky Aesthetic ™ check out my travelogue post.

The rocks below Paris are younger than the rocks we clambered on in Brittany – they’re from the Eocene era between 56 and 38 million years ago, when the Paris Basin held a shallow sea that left behind characteristic limestones and shell fossils. The sea went through periods when it very nearly dried up, leaving layers of evaporate minerals such as gypsum.

translated paris paleogeography

Image photographed by author at the catacombs, legend translated

North-south tectonic pressures slightly buckled the basin in the time since the rock was formed. This created the Meudon anticline (A-shaped fold) on the southern side of Paris, which is why limestone and gypsum from different ages are mined at similar elevations on either side of the Seine.

translated cross section of paris

Image photographed by author at the Catacombs, and subsequently translated

Left: labeled layers in the limestone, Right: teensy 5mm stalactites!

Paris has a thriving community of “cataphiles” who risk law enforcement action to explore the subterranean side of the city. National Geographic did a great special on them in 2011. Over the years since the quarries were abandoned in the 1950s, they’ve made the flipside of Paris into their playground and undertaken mapping efforts. Here’s an elegant map of the “Great Southern Network”, with notes and annotations. It’s the kind of treasure map that got me into cartography in the first place.

If you’d like to learn more, Dr. Jack Share at one of my favorite blogs “Written in stone, seen through my lens” wrote two fantastic, extremely detailed posts about the geology of Paris – one focusing on the gypsum quarries and the geologic origins of the Paris Basin, and a second one on the mines and catacombs. I highly recommend those posts, and the entire blog!


We did eventually visit the Sacre Coeur Basilica towards the end of our stay in Paris. It turns out that the basilica is quietest directly after services in the evening, and there is a lovely organ postlude. From the inside it’s a wonderfully peculiar building. Sacre Coeur was built between 1875 and 1919 and the stained glass windows weren’t added until after WWII, and so it encompasses huge changes in the French design aesthetic. The architecture is a mix of the stately Neo-classicical style like the Pantheon and the Byzantine revival style, it got a gloss of whimsical Art Nouveau statuary at the turn of the century, and ended up with weird abstract stained glass windows from the post-war period when artists felt that the world was broken beyond repair. The building is made of travertine from the Souppes-sur-Loing quarry, in the Seine-et-Marne department about 100 km south of the basilica. Travertine is an exceedingly hard, fine-grained stone that releases chalky white calcite when it rains. So basically, it’s self-cleaning and is able to stay gleaming without pressure-washing!

English-language resources:

Paris: From quarry to catacombs

A really excellent post about the mines of Montmartre:

Another very thorough post from that same author on the rest of Paris’ quarries:

reddit post hosting an AMAZING map of all the explored catacombs under Paris:

French-Language resources:

detailed post on mines, mining techniques, and mine inspection in Paris:

Crazy pink rock formations at the Cote du Granit Rose

Part 2 of the geology of my summer vacation. For an idea of where this fit in our trip, check out the travelogue post. This post follows the first post on Mont Saint-Michel.

I had left all of the vacation planning in Heather’s able hands so I could focus on my thesis last spring. My only requirement (only halfway in jest) was that the vacation had to include eating pastries on rocks. And boy, did Heather deliver! Days 5 and 6 of the trip found us near Trebeurden and Ploumanac’h on the fabulous pink granite coast. The sun was shining, the pain au chocolat was as delicious as I had ever hoped for, and a giant granite playground awaited us.

croissant and rocks

my dreams came true!

There isn’t a shortage of granite on the Brittany coast – we met some in the last blog post too. Much of was grey and only visible in isolated outcrops. As we hiked east from the little port of Ploumanac’h along the coast, the grey granite gave way to crazy piles of unmistakably pink rock! I couldn’t help but start wondering what caused the change in color, not to mention the weird shapes!

It turns out that the explanations come in threes: the pink granite is made of three minerals, it belongs to one of three different igneous events in the region, and three different substances have sculpted the granite into the wild shapes at Ploumanac’h.

The pink granite gets its rosy hue from potassium feldspar, while the greyer granite has more creamy-colored plagioclase feldspar in its makeup. I illustrated their mineral composition in the figure below. The natural history museum in Ploumanac’h informed me that the pink granite is  approximately 50% potassium feldspar, 30% quartz, and 20% biotite. They didn’t give details about the less glamorous grey granite and I was too focused on getting to the pink stuff to even take a close-up of it, so I’ve only approximated its composition.

Pink Grey Granite Comparison

Both colors of granite at Ploumanac’h were put in place around 300 million years ago (mya) during the last gasps of a mountain-building event as the ancient continents of Gondwana and Laurussia crashed together to form Pangaea. I talked in depth about this massive game of continental bumper-cars in the previous post, so I’ll skip it here. Over time erosion unearthed the buried masses of granite, as shown in the figure below.

pink granite emplacement diagram.png

Photo of a diagram in the exhibit at the Maison du littoral, text translated by me.

To get even more specific, the granite in the area was put in place in three physically distinct phases around 300 mya. In the first phase, two magmas with different compositions intruded the surrounding metamorphic rock at the same time. The first was rich in silicon and formed the coarse-grained pink granite and the second was poor in silicon and formed the dark gabbro visible near Tregastel. These two igneous rock types melted in the same event from two different types of source rocks, giving them their unique compositions.

During the second phase, another silica-rich magma forced its way into joints in the now-cool first pink granite. This magma had a similar composition  to the pink granite in the first event but cooled more quickly than its predecessor, forming smaller mineral crystals.

In the third phase, a magma with a more basic (as in pH) composition intruded into an dome-shaped weakness in the cooled granite from the first two phases. This magma cooled into the blue-gray granite near Ile-Grande.

The difference between the colors of the ~520 million year old granite at Mont Saint-Michel, the ~300 million year old grey granite at Trebeurden, and the ~300 million year old granite at Ploumanac’h isn’t merely ornamental. The rocks’ mineral compositions give geologists clues to the kinds of source rocks that melted into the granite. Feldspars and quartz have high silicon:oxygen ratios in their composition, and so indicate that abundant silica was present in the source rocks.

A whole host of different kinds of minerals are built from silica and oxygen, ranging from the densest minerals with 4 oxygen atoms  for every 1 silicon atom to the less dense minerals with only 2 oxygen atoms for every 1 silicon atom. In general, the less dense silicon-rich minerals are more represented in the continental crust, while the denser silicon-poor minerals are more common in the oceanic crust.

You can see these relationships between minerals’ properties and igneous rock types below in the igneous rock classification chart every mineralogy student learns by heart by the end of the term. It’s only a guideline – if a mineral was missing from the source rock, it will not show up in the igneous rock created from its melting. For example, amphibole and muscovite are missing from the pink granite.

This indicates that the pink granite was formed predominantly by the melting of low-density, high-silica rocks at low melting temperatures. The grey granite at Trebeurden is a little bit to the right of the pink granite on the classification chart – still a granite, but including more minerals with higher melting points and less potassium feldspar (a.k.a.  orthoclase feldspar). The gabbro at St. Anne is even further to the right, and likely formed from the melting of a chunk of oceanic crust. Sometimes rocks are completely off this chart. For example the magma that formed the pale granite that we saw at Mont Saint-Michel either melted at low temperatures (geologically speaking) of ~600 C or melted from source rock whose chemistry didn’t allow for the formation of dark mica or amphibole crystals.

So I figured out why the granite was pink instead of grey. But what created its otherworldly shapes? And where did all these boulders come from?

Usually boulders are created in steep landscapes where chunks of rock falling off the canyon walls are tumbled aggressively in mountain streams and carried long distances. In contrast, these boulders have barely moved relative to each other since the granite cooled! They were formed in place by erosion, shown in the diagram below. The technical French term for this formation is “un chaos”, which seems very appropriate.

granite chaos creation

The important factor here is a change in the rate of weathering and erosion. In this case, the erosion regime changed from slow dissolution of the rock by groundwater (shaping the granite into boulders underground) to more rapid erosion as the waves crash on the shore (exposing the boulders).

Once the boulders are exposed to the elements, two slower types of chemical erosion nibble them into even more convoluted shapes. Chemical reactions between salt spray and the the mica and feldspar crystals in the rock transform them into weaker clay minerals that wash away, creating divots and creases in the rock wherever salt collects.

As saltwater works on the rocks from the top, organic acids in soil eat away at the rocks at ground level over tens of thousands of years to create subtle mushroom shapes.

acidic soil erosion

The end result is an utter delight to explore!


Heather points out a quartz vein in the pink granite. The boulder on the center left shows a distinct salt weathering divot on its top.

pink granite castle

Climbing to the top of a formation, I found a 2-foot deep crenelated “crow’s nest” formed by salt weathering!

Sources (all are in French):

Great summary from the local natural history museum, the Maison du littoral:

Less technical summary from the local tourist board:

Long and extremely thorough field trip guide published by the Geological and Mineralogical Society of Brittany:

Short summary/technical field trip guide:


Dome Rock and the continuing trials of Jo, the Adventure Civic

Dome Rock Hike: 10/10 would hike again, magnificent view

Drive to Dome Rock north trail head: 10/10 would NOT attempt again in a 2001 Honda Civic

I had originally planned to hike the 10-mile round trip trail from the Detroit Lake information center up the ridge to Dome Rock, but the ranger at Detroit Lake State Park was quick to discourage me. He suggested that it would be much easier to take the Forest Service road to the northern trailhead and just do the prettiest 3 mile section along the ridge top. Sure! Why not?

18% average slope on gravel roads is why. Having to stop and restart my crotchety old car multiple times on said 18% slopes to move away the fallen rocks so I could get clearance is another good reason.

Luckily the beauty of the hike brought my blood pressure back down again within a mile or so. The trail wound though firs, maples, and thimbleberries (snack time!) along the ridgetop above Tumble Lake.

Map of Dome Rock trail

Map from Willamette National Forest USFS website for trail 3381

Directions to the Tumble Creek North Trailhead can be found here on the USFS site. They aren’t kidding when they say “up steep mountain roads”.


At the top of Dome Rock, selfie with Tumble Lake!


View of Mt. Jefferson and the Three Sisters from the top of Dome Rock.

I was hiking in the Western Cascades, which form the more eroded volcanic predecessor to the striking peaks of the younger High Cascade mountains. Magma rising from the subducting Farallon plate created both zones of the Cascades, but the two stages of that subduction made them distinct. Between 35 and 8 million years ago the plate sank under North America at a slightly steeper angle, resulting in the location of the Western Cascades. Around 7 million years ago that angle became shallower, which moved the depth at which the magma rose off of the melting plate to location further east. (Devis 2013)

Inkedwestern vs high cascade Miller page 110_LI

Figure from page 110 of Marli B. Miller’s classic “Roadside Geology of Oregon” – the area of Dome Rock  is circled in yellow

change in subduction zones Miller page 113

Figure also from “Roadside Geology of Oregon”, page 113, showing how the change in subduction angle influenced the location of volcanoes further inland.

All the classic cone-shaped volcanoes of the Cascades such as Mt. Jefferson, the Three Sisters, and Mt. Hood are part of the High Cascades. In contrast, a few more million years of exposure to rivers and glaciers created the more subdued landscape of the Western Cascades. Any volcanic cones from that era have long been ground down to their roots.


Standing in the Western Cascades, looking at Mt. Jefferson in the High Cascade mountains. Photo taken during one of my stops to move rocks off the road…

Dome Rock itself is one of those “roots” – an isolated piece of 10 million to 17 million year old andesite where newer magma punched through a 30 million to 17 million year old area of tuff (cemented volcanic ash) and basalt. (Walker, G.W., and Duncan, R.A., 1989) It’s relative toughness meant that it withstood the 10 million years of weathering since its formation better than the surrounding formation’s softer tuff with basalt, creating the bare knob with spectacular 360 degree views.


Andesite near the top of Dome Rock… next time I’m hiking with my rock hammer.

Jo’s engine may have nearly overheated on the way up, but at least I didn’t have to use the engine at all for seven miles on the way down. After creeping back down the forest service road using a combination of second gear and brakes, I stopped at a peaceful little day use area along Frenchman Creek to eat my lunch. Judging by the size of the boulders in the creek bed, the stream hasn’t always been so tranquil!


Frenchman Creek day use area, about 1.5 miles north of the intersection with Hwy 22

Zach Urness of the Statesman wrote a helpful article on the Dome Rock/Tumble Lake hikes with more information about the lake and its campsites. I didn’t go down to the lake this time, but maybe next trip.

With all the time that skipping the extra 7 miles of the hike saved me, I stopped by Marion County’s Niagara Park on the North Santiam on the way home. My phone was dead, so no pictures this time, but if I’m by there again I’ll definitely stop to take some. The site was ambitiously called “Niagara” by hopefuls in the late 1890s aiming to build a dam where the Santiam is funneled through a 4-foot-wide crack in the underlying rocks. The dam failed repeatedly and they gave up in 1912, leaving a park with picturesque ruins. About a half-mile up the stream from the failed dam lies a  misshapen mound of rocks eroded into a perfect picnic spot and place to cool your feet off in the river.

I was sorry to have to leave the parks and head back home… and on the way back I got Jo a well-deserved car wash.


My sister posing with Jo the Adventure Civic on another trip that I’ll be blogging about soon!

Field work: Week 2

This past week Jen and I headed back out to the Walla Walla Basin, but primarily for another project: doing the quarterly water level check and data collection download at observation wells in the Umatilla and Walla Walla watersheds. In between monitoring wells we collected the five remaining samples budgeted for the geochemistry project.

After visiting 60 or so wells, each with their standard blue wood-and-aluminum housing, they started to blur together. A few things stood out…

Cozy mouse nests and resident spidersimg_20180709_135009456

Granite boulders 200 miles from where they ought to be


and the earth-shaking exploding munitions that I was discouraged from photographing.

Those munitions were on the Umatilla Army Chemical Depot, where OWRD has a handful of  monitoring wells. Atlas Obscura has an intro and some interesting photos… The site was created during WWII to store weapons and supplies, and since then has been the location for disarmament from weapons stockpiled for use in the Pacific theater of the second World War as well as the Cold War. Our guide said that they had indeed gotten rid of all the chemical weapons stored onsite, and the current mission on the base is making sure that the old explosive weapon destruction pits are done exploding. That explosion while we were sampling was proof that the second look was necessary. The end goal for the site is to render it harmless enough for limited non-military use such as stock grazing.

Not much explanation is needed for the well housing tenants – the structures form hospitable shelters in the middle of wide-open grain fields. A perfect bed-and-breakfast for four-legged or eight-legged creatures. Luckily we didn’t see any of the region’s black widow spiders – just harmless, fuzzy Phidippus audax. For the sake of my arachnophobe friends I won’t post a portrait, but google them if you’re curious. They’re actually kind of cute.

That granite boulder, on the other hand, is a long way from home. Like, 100 to 200 miles. And it’s not a small boulder – it’s about the size of an oven.  Below is a map showing the “closest” granite outcrops in purple, and the location of this lonesome rock with a pink star. What on earth is it doing by a well in Morrow County, Oregon?

pnw granite and erratic

Like so many geological oddities in the Columbia River basin, it hitched a ride on the epic Glacial Lake Missoula floods (shown in blue below)! It likely came from somewhere around Spokane.

pnw granite erratic with floods

Glacial flood extent created by ESRI user jcleveland0, accessed via ESRI Online. Granite outcrops selected from the USGS Preliminary Integrated Geologic Map Databases of the United States shapefiles for OR, WA, MT, ID.

The Missoula Floods were an amazing manifestation of the latest Ice Age between 13,000 and 15,000 radiocarbon years ago. An ice sheet repeatedly dammed a predecessor of the Salmon river at its headwaters in Montana, creating a lake over 200 miles long. Then as water likes to do it eventually blasted through. Again. And again. In each flood event water racing at over 10 million cubic meters per second scoured the landscape in northern Idaho, Eastern Washington, and northern Oregon. These floods meant business, creating ripple marks bigger than houses, amphitheater-sized waterfalls, and topsoil stripped from Spokane to be deposited in Salem. That flow picked up boulders the size of buses only to set them down them hundreds of miles away, so the moderately sized one we saw on our rounds would have been a piece of cake.

The Washington Geologic Survey created a beautiful, user-friendly introductory website for the floods here. I really recommend it! It not only shows the scientific knowledge surrounding the floods, but the process of science that connected all the disparate observations into one phenomenal story. At least, phenomenal if you’re as nerdy as I am.

Our own research for the week was unfortunately nowhere as riveting as this rock’s journey. In the coming weeks I’ll wait with bated breath for the laboratory results, learn how to process four months of water level transducer data for a few dozen wells, and start my literature review. However any blockbuster geologic story like the Missoula floods was assembled out of thousands of seemingly trivial observations, so I’m happy to work away in my own little corner of science.


It’s not a bad-looking corner at all, just a bit hot…

Strike, Dip, and Skis

Hoodoo summit

Mt. Washington selfie on top of Hoodoo Butte!

It’s been something of a theme in my recent blog posts that the west-coast mountains are a source of nerdy joy for this recently transplanted geoscientist. This winter I went on my department’s grad student ski weekend to try out this whole zooming-down-mountains-on-sticks thing and get a chance to hang out at Mt. Bachelor with a convivial bunch of folks. I got thoroughly hooked despite spending much of my time crashing on the bunny hill and watching the 4-year-olds effortlessly ski past me. It’s a whole new way to appreciate the volcanic history of the northwest! (hmm, that sounds like a blog post series once this term is finished…)

Two weekends ago I progressed to wiping out on the blue-level slopes instead of the greens (baby steps!), and a thought hit me out of the blue that dramatically improved my control over my skiing.

‘What would a Brunton compass tell me about this line?”

I promise I hadn’t hit my head and lost my marbles on the previous “yard sale” fall where my scarf, poles, and skis ended up strewn around me. For my non-geologist readers, a Brunton compass is the strange but useful combination of a compass, mirror, and level that geologists use to measure the dip (steepest angle) of a tilted piece of rock as well as the strike (cardinal direction perpendicular to dip, and the direction where the Brunton is completely level).

I was skiing down the Glade route at Timberline and my trusty “aim to the edge of the run to slow down” method was failing me miserably half of the time. I had a flashback to the last time I was in mountains, swearing at my Brunton at Indiana University’s field camp in the mountains of Montana. In that moment of clarity I realized that if the mountainside was a tilted rock layer I was expecting the route to be perpendicular to the strike (true dip, i.e. straight down) while it was actually at an angle (following a shallower apparent dip). By aiming to the edge I was going to the steeper true dip and accelerating – exactly the opposite of what I wanted to to do!


It’s a universal truth in physics, particularly noticeable for people who ski or mountain bike, that the steeper your trajectory the faster you’ll accelerate. Friction determines the maximum speed. In my case gravity conspires with my properly waxed skis to set my maximum speed on the steeper blue routes much faster than I have the skill to control, hence the wipe-outs.

If the route is straight downhill following the “true dip” of the geologic example, I can ski either to the right or left to decelerate to a more comfortable speed. This holds true for the “Over Easy” route I first skied/slid down at Mt. Bachelor, most routes at Mt. Hoodoo, or for the Magic Mile routes at Timberline. These routes are aimed pretty much straight down the side of the mountain.

true dip skiier

However if the route is at an angle to the steepest possible line, then it is following the geologic “apparent dip” of the landscape. In that case, if I ski to my right, away from the angle of the route, I would find myself skiing at a steeper angle towards the true dip and accelerating into a snow bank.

apparent dip skiier

Geology students find ourselves tripped up in less spectacular ways when faced with eroded inclined structures, where the true dip of the rock bed isn’t perpendicular to the eroded top of the formation.


Week 5 of field camp: why the heck is the hillside shaped like an “M”?

On a contorted landscape like these hills near Doherty Mountain in Montana, it was all too easy to ignore the wobbling level bubble in my Brunton compass in the rush to finish surveying an area. After the first day we all put our notes together and realized that none of us agreed on the dip of the hillside. We had been fooled into interpreting the easiest path to walk across the hill as “horizontal” and measured various apparent dips.

apparent dip geologist

As enjoyable as my class made it to trek up those hills through the bushes and snakes, wouldn’t it be even more fun to ski  down them over a nice smooth blanket of snow…


Applying to graduate school with Courtney and Beaker


If personal narratives aren’t your cup of tea I totally understand if you want to skip this post and wait til I post something involving rocks (Road trip part 4 is coming soon, I promise!). I’m writing this post for those who stand where I stood in May 2013, struggling to define their academic goals and career path.

Tl:dr version: You aren’t alone if you don’t have any idea of what you want to do for grad school or careers straight out of undergrad. Take the scenic route, try out jobs, and ask a lot of questions!  And just like in any scientific endeavor if you fail, take a good hard look at your methods, gather a team, and try again.

If I hear someone say “You can do anything!” one more time, I will probably have an allergic reaction that causes me to sprint out the door and down the street while making small panicked noises like Beaker in the Muppets.beaker_meep__meep__meep__animated_badge_by_blue_staple_studios-d94gpzx

(possibly my spirit animal)

‘Tis the season for graduate school applications, so I thought I’d share how I ended up at Oregon State! It meant taking some relatively risky moves instead of the safer option of staying in one place, as if my true calling would one day show up on my doorstep if I was patient enough. This was nerve-wracking but rewarding and involved doing things like decamping to California for a seasonal job, or prying myself out of my introvert shell to cold-email dozens of people. Early in the process of thinking about graduate school, when I heard a well-meaning “you can do anything you want!” some part of my brain translated it it to “you should do everything, if you aren’t then you’re failing, and what if you miss an opportunity of a lifetime while you’re doing something else?”

Because of that fear of commitment, graduate school application was initially an intimidating process for me in my senior year of university. Grad schools require a different mindset than undergraduate programs to apply because the academic and personal fit between the applicant and advisor is so crucial. There’s no Princeton Review guidebook to give a tidy 1-100 ranking of schools. I didn’t even know how to formulate the questions to get help choosing a program then. I would have needed my advisor to dive inside my head and read my mind, which is still firmly in the realm of sci-fi. Talking to grad students at Vanderbilt, they made it seem so effortless to make up their minds about what subject they wanted to devote 2-6 years to. It flowed out of an undergraduate research project, or a natural interest, or something that “just made sense”.

It didn’t help that, by the fall of my senior year, the interdisciplinary major that I had designed to study climate change was revealing to me exactly how complicated that issue was and how it could weave itself through any narrative I looked at. Did I want to study paleoclimates, or atmospheric sciences, or environmental justice, or energy sustainability, or…..? Indecision froze me like a deer in the headlights.


Beaker trying to disappear

Several different possible paths occurred to me that spring of my senior year. I could go into private or public research, which would eventually require a higher degree and those mystifying applications to graduate school. I could look into becoming a park ranger, guide, or outdoor educator, based on both my academic and non-academic passions. I could go into the nebulous field of “consulting”, based on a conversation at an environmental careers dinner. So, I figured that it would be best to try them out.

To start off with I got a fantastic GeoCorps internship at Mammoth Caves National Parks, where I learned that being a park ranger involves unlimited outdoor time frolicking through natural science (and facilities maintenance), but also finding a new posting every six months and a best-case scenario of being promoted to a stable management job where I would be banished to an office.

Who needs free weights when I have a hammer drill and a 6-mile hike to the cave entrance?

With a bit of legwork I got a position as an intern at an environmental consulting firm where I learned the nuts and bolts of regulations and customer service, and how complicated it is to balance clients’ business interests and the environment.

C with tanks.jpg

After the terms of that internship came to a close I headed out to California to work for Naturalists at Large, where I learned that no matter how much I can geek out over geology, rock climbing, and birds, keeping classes of middle school students amused is not my forte, and neither is finding a new outdoor recreation gig every single season.

This process of elimination left grad school, probably earth science as a career, and my nature cravings as a side hobby.

While in California I had applied to Indiana University’s summer field school (and only that one field camp, because I still felt like relying on dumb luck), because I figured that if I were to go the grad school route I would need it. In a ringing endorsement for dumb luck I got in, and it changed my life. No, seriously. I was doing science! I didn’t have to worry about whether I was cut out to be an earth scientist, because I was doing the earth scientist things, and doing them well! Hiking around the Tobacco Root Mountains of Montana wasn’t half bad either.

Stream temperature experiment/pool party at the Firehole River in Yellowstone National Park

In hindsight, field camp bumped me up to about 40% ready to apply to graduate school from 10%.

The next 20% was acquired over months of job applications, paper-reading, blog-writing, talking informally with professors and professionals, tutoring middle- and high- school students in earth science and English literature, volunteering with a USGS data analysis project, and getting hired full-time at the environmental consulting firm where I had interned. I went to visit professors at University of Pennsylvania, University of Delaware, and Johns Hopkins while living on my sister’s couch for a few weeks, which gave me practice talking with professors, a sense of how graduate programs were structured, and desensitized my anxious self to interviews. Volunteering as a data analyst with the USGS gave me an additional recommendation-letter-writer as well as experience with data analysis! Through all that, I narrowed down my impossibly wide interest to water issues stemming from climate change, leaning towards quantity instead of quality.

The last 40% was gained in four months of targeted cold-emailing of potential advisors, phone calls with those professors, obsessive research in my field, and a 2015 Geological Society of America conference where I walked up to random people and piped up “Hi, my name is Courtney, I’m currently working in environmental consulting, what do you do?” followed by a few minutes of listening, followed by “where should I go to graduate school to study how climate change and human use patterns affect water resources?”. You’d be surprise how well that works. It’s shockingly easy. If you had told me in my senior year of college that I would do that 15-20 times in a day I would have backed away quietly with a polite and petrified grin plastered across my face. Geologists being a friendly bunch, sometimes people told me “ask that guy over there, I’ve got no clue”, and most were happy to give me a lead or two.

I explored civil engineering, hydrology, geology, and geography masters programs. Because of my interdisciplinary interest, I ended up focusing on large state schools that had the breadth of faculty and funding to have created a dedicated working group for water resources. I had enjoyed creating my own major in college, but wanted the stability of an existing program to give my Masters degree more weight and to not have to explain it in detail to everyone I meet. Geography programs really stood out here – Vanderbilt didn’t have a department in this field, but I realized that it was pretty much perfect for me!

Based on all of these conversations at GSA and elsewhere, I figured out what angle I wanted to take on “water issues stemming from climate change, leaning towards quantity instead of quality” – geographical methods, instead of strictly hydrological or ecological.

Then I made a spreadsheet based on that info, and set about fleshing it out.

grad school spreadsheet screenshot.png

It has 34 rows, one for each potential advisor I contacted at twelve schools.

This might give the impression that I’m a naturally organized person who loves cold-calling, which isn’t the case. It’s challenging for me and sometimes prompts me to curl up in a blanket at 5:30 in the evening with soothing instrumental folk music. However, it’s the hurdle to get to science that I love and opportunities that I need, so I made myself the tools to get over it. I set a goal of four professors or current grad students contacted per week, and met it most weeks. I found out that no matter how many intelligent questions I think of before I call a professor, they will all fly out of my head once I’m on the phone unless they’re written on a sheet of paper in front of me, preferably in several eye-catching colors of pen. I have a wonderful sister who will reassure me that I’m a worthwhile person when I text her at midnight after hours of tying my thoughts in knots about an awkward conversation. Spreadsheets help me fish thoughts and information out of my brain, put them in words, and manipulate them in a useful way.

For example, University of Arizona took about 10 hours of research, 3 calls to current grad students, 3 calls to faculty, and a spreadsheet of its own to sort out the tangle of water research options and who teaches where.

u of a spreadsheet screenshot.png

Based on all that information, I narrowed my choices down to geography programs at five universities. That done, I had to make it easy enough for myself to keep track of the five applications that I would actually complete them and not forget anything. This meant another spreadsheet… and a whole lot of refreshing my email inbox.

apps spreadsheet screenshot.png

And after all this work, I got into exactly 0 schools in the spring of 2016. For reasons related to over-committed professors, funding cuts, and the fact the I applied to the most competitive programs in my field, I wasn’t judged to be a suitable enough fit to accept and fund. April was a pretty ghastly month for my mental state as I frantically tried to piece together another timeline for my life that didn’t involved driving off into the sunset towards a graduate program in August 2016.


Beaker’s file being tossed…

I allowed myself about two solid weeks of denial, self-pity, and comfort food, and then I reached out to some lovely friends who shut down the pity-party. We made a list of next steps:

  • Reach out to the schools to request a post-mortem of my application
  • Take the ASBOG exam to work towards professional development and freshen up my geology skills
  • Continue with my current job
  • Take a statistics course
  • Write appealingly nerdy things on my blog
  • Get a gym membership and start climbing again with my newfound free time
  • Restart the grad school search in August 2016, and try to focus it more on research
  • The silver lining: I now had an extra year to make myself that much of a better candidate.

In the fall of 2016 I reapplied to Oregon State and applied to San Diego State, University of Waterloo, and Southern Illinois University using the same tools and all that knowledge I had gleaned from potential professors/advisors in 2015. I had described a broader focus on my 2015 applications, but had focused my interested down to the geography of groundwater management during the 2016 applications. This 2016 specialization allowed me to better pinpoint potential advisors and make the case for how I could fit into their programs, and also probably made me look like a more committed candidate on my applications. I figured that if I had gotten into 0/5 schools in 2016, I might get into 1 out of 4 schools in 2017.

What did I do differently?

  • Reached out to professors earlier in the fall
  • Had a more defined research interest
  • Asked more specifically if they had research they could fund me for, or if not who in their department did
  • Posted on the Earth Science Women’s Network Facebook page asking for recommendations of schools with ambitious and possibly underrated groundwater faculty that weren’t on my radar
  • Stayed in closer contact with my letter-of-recommendation writers

In the spring of 2017 I won the grad school applicant lottery – I got into all! Four! Schools! All the important people in my life had to deal with text messages IN ALL CAPS ALL THE TIME HOLY MOLY.


Beaker playing “Ode to Joy”!

I hope that the takeaway of all this is that if you’re applying to graduate school, you need to talk to people. As many people as possible. This was my biggest obstacle when I first started applying – I didn’t want to bother anybody. Additionally, I was ashamed to ask for help even when I knew how to articulate my questions, as I thought it would make people think I wasn’t good enough to begin with. Eventually I learned that few people are bothered as long as I did research beforehand to avoid asking them to regurgitate the contents of the personal website for my benefit, which nobody has any inclination to do.

I found that academics, students, and professionals alike generally like talking about what they do and helping people out if they’ve got the time. An applicant can take respectful advantage of that to learn what’s out there. The worst anybody can say to you is “no”, and it’s almost never personal. It boils down to seeing if the professor is doing what you want to study and has funding, and then convincing them that they really do need your unique talents and brainpower.

And don’t worry if those talents change from conversation to conversation, especially if you have an insanely broad initial focus like I did. I settled on a messy process of deciding on a certain way of selling my skill set to a potential advisor so they would at least talk to me, using what I learned from that conversation to improve my focus, and then pitching that improved focus again or to another professor. Sometimes I talk about different research ideas with different potential advisers, just to see which one I enjoyed talking about the most. I had barely managed to pull together a coherent idea of a academic goal as I careened into the December 2015/January 2016 deadlines, and came up with the new and improved version 2.0 by December 2016.

If I have to pick a metaphor for finding my calling after college, it’s less like a package delivered to my doorstep and more like a Pony Express run to deliver a shapeshifting package to an address I can only find at the end of a scavenger hunt. But I made it, and you can too.

Happy trails!

If you want to pick my brain, to commiserate, a copy of my spreadsheets to use as a template, or advice for cold-emailing, let me know in the comments.