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.

from https://oaklandgeology.com/2015/05/04/oaklands-serpentinite-patch/

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 🙂

References:

• Nick Zentner on Ingalls Ophiolite: https://www.youtube.com/watch?v=mfFqEmEYvOI
• The big primary source: Wenatcheee Quad Geologic Map: https://pubs.usgs.gov/imap/i1311/
• https://blogs.agu.org/georneys/2011/02/10/geology-word-of-the-week-o-is-for-ophiolite/
• Nick Zentner Ingalls and Easton terrane story https://www.youtube.com/watch?v=URtNdXMS6ww
• Info on the local glacial timeline: http://faculty.washington.edu/tswanson/ESS/302/ESS%20Readings/Porter1976.pdf
• Info on how serpentinite affects vegetation: https://www.fs.usda.gov/wildflowers/beauty/serpentines/adaptations.shtml

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Goats and surprises – Beverly Creek to Lake Ingalls

It’s been a while since my last “hiking geologist” post. It’s not because I haven’t been hiking! It’s one of two reasons – 1) I’ve been hiking in the same area that I’ve written about previously or 2) I had an amazing trip in the Olympic Mountains and I haven’t wrapped my head around its geology yet. But over Labor Day I checked out a new-to-me area on the doorstep of the Enchantments and felt like a kid in a candy store. Green glassy rocks! Ribbons of igneous dikes? Rocks that look like sandstone from afar but igneous up close. Lots to make me curious, so here we go. This is the hiking post, geologist post to follow.

On Saturday morning I rolled up to the Beverly Trailhead in the Okanagan-Wenatchee National Forest north of Cle Elum. Although I had left Seattle’s rain behind when I crossed Snoqualmie Pass, low clouds still sat over the Wenatchee Range. They hung like a roof over the North Fork Teanaway valley once I passed Cle Elum. I parked next my silver Subaru’s twin (minus the Caution: Geologist Driver bumper sticker), hoisted my backpack onto my shoulders, and headed uphill. Here’s a regional map for context, and a map of my hike so you can follow me around on my hike.

I hadn’t backpacked in a while and my cardiovascular system was protesting. The breaks gave me a chance to survey the view once I got out of the trees. It looked quite a lot like the approach hike to Mordor in my opinion. The dark peaks crumbled down their slopes in gully-carved run-outs. A few hardy trees stood their ground. It looked very different than the granite landscape I was used to exploring off of Highway 2. At least I heard some pika chirps to encourage me.

The sun came out once I had hauled myself 2.7 miles to the junction with the Fourth Creek trail. Lunch was a welcome pick-me-up, eaten once I felt I couldn’t hike any further without having a minor meltdown. The rest of the climb to Turnpike Pass was easy! It wasn’t any less steep, but I was drawn on like a magnet by increasingly shiny exposures of green-tinted rock. It looked like glass and was broken in convoluted folds, nestled into white stone like butter in croissant dough. It lead me up to the top of the pass, with views of the head-water marshes of Beverly Creek to the south and a tantalizing glimpse of Mt. Stuart to the north through the trees.

Honestly, the Turnpike Trail is not great. It descends through an accidental creek full of loose cobbles. It has one view going for it – the trail opens up above the last descent to Turnpike Creek into treeless switchbacks through talus slopes of orange rock and more of the green glassy stuff. I stopped for a snack and to watch jays argue in the ponderosa pines below in the valley. After the steep descent the trail was mostly flat until a smaller drop down to Ingalls Creek. Just before that drop I encountered shallow domes of light orange rock. I confidently assumed it was sandstone. Research would prove me wrong, but more on that later.

Once I had crossed Ingalls Creek and thrashed my way up through meadows of bloomed-out wildflowers, I sat down for a break on some familiar rock. Bright fresh granite, white with black flecks. The bug sounds in that top meadow were so peaceful. Those moments are the reason I backpack. I hung a left on the Ingalls Creek trail and headed to the Ingalls Creek campsite like a horse towards its barn. That is, if I could find it. It wasn’t where I expected it to be. I pushed too far uphill on the Ingalls Creek Trail through dense thimbleberry bushes until I was properly cranky and had to sit for a moment to get my head on straight. I decided to head back downhill to the trail junction, which turned out to be correct as the campsite is actually on the Longs Pass trail. I arrived in time to claim an absolutely primo campsite of pale granitic sand nestled between boulders right by Ingalls Creek. Later in the evening, climbers rolled into other campsites in order to climb Mt. Stuart the next day.

I woke up to an absolutely perfect morning on Sunday and headed up the Ingalls Creek trail to Lake Ingalls. The last red paintbrush flowers bloomed by the creek. After passing 2.5 miles of berry-less blueberry bushes and granite boulders, I finally found a patch on the Ingalls Way trail to snack on, growing on the same orange rock that made up the otherworldly domes to the south of Ingalls Creek.

Note: the Gaia GPS app shows three “trails” that split as “alternatives” to get to Lake Ingalls from this direction. A lower elevation route, a middle elevation route, and a route along the tops of the ridge west of Stuart Pass. Only the middle one is legit. The high path along the ridge is an unmarked scramble and the lower route through the meadow is a boot path that damages the landscape by cutting through marshes and overly steep terrain. Plus only the middle route has blueberries.

After a fun scrambly half-mile I made it to Lake Ingalls and had it all to myself! I found a beautiful spot by the blue water to make my day camp and break out chocolate and a book. Reason # 2 that I backpack. Then I headed off to clamber on the irresistible rock formations. Truly a playground for all ages, if you hop between rocks to avoid trampling the vulnerable alpine plants. I met a marmot with the best view of Mt. Stuart who was sunbathing and not caring at all about me. Little chipmunks were less bold and scurried away as I jumped from rock to rock.

Mt. Stuart from the Ingalls Creek Trail

Lake Ingalls

Orange rocks and Mt. Stuart

Can you spot the marmot?

Interlopers in the orange rock formation caught my eye as I rambled south along the lake shore. Elongated mounds of gray rock nestled among the orange domes, and a long ribbon of gray zigzagged up the southern side of Ingalls Peak. As I went to investigate them, I ran into a darling family of mountain goats – Big, Medium, and Baby. They were ambling down the trail so I went rock-hopping to give them their personal space. They’re so fluffy, but the horns on Big and Medium looked wickedly sharp.

A gray interloper

close-up of gray rock

Goats!

By this time more people had showed up, but almost all had come from the Esmerelda trailhead on the southern side of the lake and stayed there, or on the west side of the lake. I wondered if I could join them from the eastern side and climbed up a huge playground of sloping rock formations. I was stymied by a sheer cliff on the western side of it. I went to go back down but the goats had blocked the gully I had climbed up so I took a reading break to wait for them to clear out. From my perch I saw a bold hiker decide to skinny dip in the lake, and then run screaming out from the cold.

Around 3pm the wind picked up and a light rain started. I scrambled down the side of the big knob of rock to avoid the lingering goat family. Several more marmots shrieked at me as I made my way along the eastern lake shore past the skinny dipper now wearing a puffy jacket. A big billy goat blocked the trail again, giving me a happy excuse to climb the rock playgrounds. The downhill hike back to camp was a romp. I ate my boil-in-the-bag dinner and chatted with tired climbers heading back from conquering Mt. Stuart.

A rowdy flock of bushtits work me up the next morning and I decided that I wasn’t going to return by the steep Turnpike trail. Instead, I would hike another mile down the Ingalls Creek trail and hang a right on the Fourth Creek trail which looked like a more gradual climb on the topo map ( I use both the Gaia GPS app and a paper map). It was sunny and perfect hiking weather, especially when I caught a bit of a breeze. That mile between the Turnpike trail and Fourth Creek trail junctions was a hot mess of downed trees but the Fourth Creek trail itself was absolutely ideal. There’s a big horse-camp site where it crosses Ingalls Creek, and the Fourth Creek trail itself is maintained for horses with minimal blow-downs. Adorable Douglas fir squirrels scolded me from the trees and I saw an elusive Clark’s nutcracker with his bold white and gray coloring. The trail crosses rocky Fourth Creek a couple of times. Fourth Creek Pass overlooks a big bowl of meadows and the craggy Mordor-like Bean Peak and Volcanic Neck. I would love to come back here in the early summer – I bet the wildflowers would be spectacular!

Once over Fourth Creek Pass, I met up with the familiar Beverly Creek trail. The landscape was much less depressing in the sunshine. I was properly tired out when I made it back to my car. I stopped to full up my water from the creek at the North Fork Teanaway Dispersed campground , where a trail lead down to an outrageously clear blue creek. Seriously, it was the platonic ideal of a swimming hole with bedrock walls scoured into sinuous shapes. I soaked my feet and pumped water through my filter in a tiny inlet shaped like a hot tub. I drove back south to meet I-90 on a beautiful winding back road through the Teanaway valley and golden fields.

In my next post, I’ll dive into the rocks that distracted me and their origin. A hint: These rocks are ALL interlopers – part of an accreted terrane. But this terrain came from a deeper source. I was hiking through an ophiolite, a piece of the mantle beached on the continental crust like a whale on a beach. More on this next time!

License to Geologize! I passed the ASBOG PG

It’s almost October, which means that it’s almost time for the Fall sitting of the ASBOG exams. Also about time for me to finally finish this post!

I showed up to the convention center in Tacoma on a cloudy March afternoon along with about 50 other geologists to sit for the ASBOG Practice of Geology exam. I’m usually pretty good at standardized tests and the FG only took me about 2.5 hours, so I thought I could get out of there in time for a well earned happy hour.

Nope. I was sweating down to the last minute on the clock.

But two months later I found out I passed!

In this post I’ll share what I learned about the exam, how I studied for it, and how I applied to take it.

The ASBOG Balrog has been stamped out! (with enthusiastic permission from the artist)

I methodically worked through the Reg Review textbook again to study for the P.G. My company also had a couple of extra practice tests available. The ASBOG website has been getting more and more useful over the years – they have a good list of resources. There are free practice tests in the ASBOG Candidate Handbook. I put together a YouTube playlist of videos I found helpful too. If you can figure out a theme of the videos, you will have discovered my weaknesses…

The topics of exam questions change year to year. I got lucky in a way – the test writer chose to put a lot of remote sensing and geomorphology questions on the exam that my recent M.S. in geography set me up well for. The amount of questions about time and distance drawdown tables gave me a scare during the exam; I totally blanked. There was a question where I could have sworn the writer made up the words to trick us but it turns out that pozzolanic material is actually a thing. I was very glad that I had brushed up on the terms for the equations for petroleum yield. The exam gave the equation, but not the conversion factor from cubic yards to barrels. I was also glad I memorized the hydrogeology equations.

Comparing the PG to the FG, I found that the difference wasn’t so much in the difficulty or setup of the questions as in the topics of the questions. Less stratigraphy, more engineering and hydrogeology. Unfortunately, just as many picky mineralogy questions. More of the questions had applications, such as minerology related to concrete mixes. 5 or 6 questions out of the 100 covered business ethics or best practices. The ASBOG compares the two exams on page 15 of the candidate booklet.

Just like when I took the FG exam in Tennessee, the process of applying to take the PG in Washington was enough to make me want to tear my hair out. I submitted my documents in November, and then didn’t hear anything back from the DOL so I thought I was good. It turned out that unbeknownst to me the Washington DOL databases were hacked and frozen. When I did a casual email check-in in early February the staff let me know that they no longer had anything on file for my application. Cue frantic outreach to my references, universities, and a Hail Mary pass to the ASBOG organization. The DOL staff were very kind and helpful once they realized I had been caught up in the hack/freeze.

Deadlines – of course they vary state by state. There are two layers of bureaucracy – state and ASBOG. I took the March 18 exam and the deadline to submit the state and ASBOG documents was January 31 for the state of Washington. The document submittal deadlines are not published on either the ASBOG site or the Washington Department of Licensing (DOL) site, so I’d recommend compiling your documents and emailing your state’s department of licensing at least 4 months in advance of the exam date to find out the deadline. ASBOG does publish the exam dates, found on the ASBOG website here.

Here is a rough timeline of the steps to take the exam. Each state will have their own procedures – Washington State’s are found here.

1. Contact your state’s department of licensing to find out the deadline. This is the time to stop worrying about sending the DOL too many emails. You will be “bugging them” for a couple months now.
2. If you took the ASBOG FG in another state than you are taking the ASBOG PG, send a form from the PG states licensing department’s website to the FG state’s department of licensing. This will prompt the FG state to send another letter back to the PG state verifying that you took the FG. They will not, however, share your transcripts.
3. If you took the ASBOG FG in another state than you are taking the ASBOG PG, order all of your official school transcripts and have them sent to the PG state DOL.
4. Check the state DOL website for their recommendation forms and have two references fill them out.
5. A fee isn’t charged in most states for the PG if you also took the FG in that state. Check with the DOL. I had to pay a fee again because I took the FG in Tennessee and PG in Washington.
6. Email the PG state DOL to make sure they got the FG verification, transcripts, fees if applicable, and recommendations. This is the only way to make sure they actually came through.
7. Once the state DOL has verified that you can take the exam, they’ll send you forms to fill out for the ASBOG.
8. They’ll also send you a link to pay the ASBOG directly for their fee.
9. You now have month and a half left to study. Good luck!

Sweet Rocks in the San Juan Islands

If you like orcas, Canadian layered bar cookies, and rocks that are related to said cookies, read on!

Like many families in 2020 and 2021, mine had multiple false starts trying to plan this vacation during the brief periods of 2020 when society was trying to come to grips with how much we’d have to shut down to protect our communities. But finally in July 2021 the van Stolks made it happen. We loaded up a rental car and boarded the ferry to Friday Harbor on San Juan Island to kick off four days of hardcore relaxation.

My sister and I decided to surprise our parents with a whale watching tour with Maya’s Legacy. We thought it would be a nice nerdy cruise with naturalists even if, as the staff said, we weren’t guaranteed to see whales. Boy were we ever the luckiest though! More on that later. We left from Friday Harbor and cruised around the path on the map below.

Map of our wildlife tour itinerary – see top right for spoilers 😉

The boat cruised past the north coast of Flattop Island to admire the varied lounging positions of happy harbor seals. While we were at it I also admired the stunning layered rocks the seals were sunning on. These neat layers of nearshore sandstone, cobble conglomerate, shale, and storm deposits were laid down on some foreign coast during the Cretaceous period. That foreign coast collided the western shore of North American in the late Cretaceous between 100 and 84 million years ago. This process is very similar to what I wrote about in my post about the Oregon Coast – we meet accreted terranes once more. The San Juan Islands are a whole series of geologic immigrants, separated by five large thrust faults.

So I looked up this formation when I got home in my handy “Roadside Geology of Washington” and had to laugh. That layered formation is part of the Nanaimo Group. If that name is familiar, you likely know it from a layered Canadian treat with a nutty chocolate graham cracker crust, vanilla custard, and chocolate ganache.

A very scientific comparison (c) Courtney.

The rocks in the Nanaimo formation (pronounced nuh-NYE-moh) occur north of the most northerly thrust fault in the San Juan Islands, the Haro Fault. This fault shares a name with the Haro Straight – the boundary between Canada and the US. These rocks on Flattop island have more geologic allegiance to the Canadians than to the rest of Washington State, but with desserts like Nanaimo bars in the game you can’t blame them.

The sediments that make up the Nanaimo group eroded off of a large accreted terrane/mini-continent named Wrangellia that makes up most of Vancouver Island and southern Alaska (think of the Wrangell Mountains) as it was colliding with North America between 90 and 65 million years ago. Coarser sediments were deposited when sea levels were lower, and fine grained sediments were laid down as sea levels rose. Between the sporadic movement of the terrane and other causes of sea level change such as glaciation, the sea levels varied enough to result in frequent flips of sediment type.

Not my MS paint cross section – Steven Earle of Malaspina College drew this cross section of the deposition of the Nanaimo Formation.

After greeting the seals and the rocks at Flattop Island our captain Dave aimed for a pod of orcas he heard was northwest of Sucia Island. This small island looks like an absolute paradise for kayak-camping, and is made of the Eocene sedimentary rocks that got eroded from the mainland side of the Salish Sea and layered on top of the Nanaimo group. These rocks are the orange layer labeled “tertiary rocks” on Steven Earle’s image above. Dave threaded the boat past the high stone reef north of Sucia Island where more seals sat with their heads just above the waves. We join a couple other tour boats as they followed a family of orcas on the hunt! There was one more professional hanger-on in contrast to us tourists- a NOAA scientist with a net trailed behind the pod in a little boat to scoop up anything interesting left over from their prey.

Lee the naturalist ID-ed the whales by comparing their fins to a digital yearbook of locals. This family was Biggs orcas (formerly known as transient orcas), distinguished by their preference to hunt mammals like seals and smaller whales. We followed this family for a little while, all starry-eyed about beating the 80% chance of seeing the Puget Sound’s most famous residents. Then Lee and Dave decided to take a risk and turn the boat west to try and find another pod they had heard of. The boat made a beeline towards the oh-so-scenic Phillips oil refinery. But here in shallow water we found more orcas!

• 

• 

Mama and baby orca, and the big male orca circling our boat!

Tours have limits on how close we can move towards them in a boat, but the whales kept swimming closer. And closer. Eventually Dave killed the motors on the boat so we wouldn’t have a chance of hurting them. We lost sight of them for a moment until the boat started rocking and a HUGE male orca appeared within a wave beside the boat. A second later, in the next wave, we saw the face of a juvenile harbor seal who knows he’s in big trouble. He dove away and in close succession the large male, two adults, and two juvenile orcas started circling the boat. But where was the seal now?

Turns out he was an intelligent and resourceful seal, so he lodged himself safely between our boat’s propellers where the whales couldn’t grab him.

• 

He rested there for 10 minutes or so while the guide considered shooing him away. He ended up disappearing on his own accord. The guide said he dived and can out-compete the whales in a breath-holding contest. The whales eventually moved west with us in search of an easier dinner. I loved how the baby whales were frolicking around doing little belly flops out of the water! Talk about an ideal day.

Last but not least – a review of Nanaimo bars. After consulting with my mom (an authentic Canadian), she says that the one I bought was about 6 times the size of the Nanaimo bar she grew up with. This makes so much sense! I couldn’t come close to finished the bar in one sitting – the white layer has a texture in between cake icing and fudge. Basically pure sugar sitting on top of a coconut, chocolate, and almond crust. Topped with a layer of chocolate ganache. A delicious sugar overload to share with friends.

Resources:

• Geology of San Juan Island and environs: https://www.dnr.wa.gov/Publications/ger_ofr2003-17_geol_map_rocheharbor_100k.pdf
• Information about Nanaimo Group: https://web.viu.ca/earle/mal-cut/nanaimo-group.pdf

Helenite: can volcanoes really weep gems?

If you are on this blog, you know I’m a nerd. You’re probably a nerd too. Have you ever considered your nerd origin story? Mine began at age 7 or so in the basement of my grandparents’ house in Ottawa, Canada. Behind the washing machine and toy trains, the walls were lined with DECADES of National Geographic Magazines to pore over while the grown-ups wanted me out of their hair. When I was 9 they gave me a subscription so I could amass my very own giant yellow pile of nerdy heaven with priceless pull-out maps. I have an everlasting affection for this magazine. But it’s not the main content of the magazine I want to write about today.

It’s the ads.

In every edition, there’s at least one ad selling the reader some rare, shiny thing – a coin or a gem. The format hasn’t changed since at least 1975. The ad is full of small text raving about the product. There’s a close up with photoshopped sparkles, and a free gift with purchase. This month’s shiny trinket feature seemed tailor-made to my inner magpie. Gems? From a volcano? In my state? How can I be a geologist and never learn about a volcano spitting out gems before!

It, uh, turns out that volcanoes don’t actually spit out gems. More on that in a bit.

First off let me point out some of the positives from this ad, lest I seem too harsh. Helenite is shiny! very green! fairly cheap! 3/3 for Courtney’s inner magpie points. But there is a suspicious amount of purple prose in the ad. Let’s see what a quick google search will reveal.

The ad implies that helenite is a gem linked to the eruption. It weasels out of saying that the gem is naturally created or manufactured, but most people automatically link gems with being natural. The ad also hypes its rarity. Unfortunately they are false on both points.

Mount St. Helens erupted in 1980 in the southwestern corner of Washington, and blanketed the surrounding area in 540 million tons of ash. To give some context, 540 million tons is equivalent to 531.5 USS Nimitz nuclear powered aircraft carriers. Is the raw material rare? You be the judge.

USGS map of ash distribution

The suddenly ashen forest immediately surrounding the mountain was owned and logged by the Weyerhaeuser Company. The helenite legend goes that when Weyerhaeuser went in to salvage their equipment that had been caught in the crossfire, they found a strange effect. Their acetylene torches reacted strangely with the ash as they tried to free their machines. The heat from the torches fused the ash into a novel green glass.

Photo of uncut helenite, from geologyin.com

Of course anything shiny will draw people trying to make a buck, so now helenite is marketed and readily available as a cheap alternative to emerald, or as a souvenir. It’s softness gives it away – it’s only about 5.5 on the Mohr’s hardness scale that ranges from 1 (powdery) to 10 (diamond). An emerald scores 7.5 to 8 on that scale. Manufacturers also add cobalt or gold powder to add a blue or red tint to the finished product, so helenite is sold in a range of colors besides green.

And there have been some studies done that cast doubt on whether helenite is actually made of pure Mount St. Helens ash after all. A 1988 study published in Gems & Gemology melted known Mount St. Helens ash and compared it to a s purchased specimen of helenite. The study found that melted ash from the eruption looked like obsidian – dark gray, not green. The author used x-ray fluorescence and found out that the ash had much more iron and titanium in it which gave the dark gray melted ash its color, and higher quantities of aluminum which made the melted ash melt at a much higher temperature. The genuine Mount St. Helens’ ash melted at 1,300 degrees F, while the helenite melted at 800 degrees F. This variation is much more than you would expect, even given that ash composition within an eruption can vary. I made the dual pie charts from the information in the paper to compare the composition of genuine ash with the composition of green glass…

Even with some canny google searching and combing through the US Patent office, I couldn’t find out who actually manufactures helenite that is sold by jewelers, or how they obtain the ash. Maybe I just have to do an Indiana Jones style Hunt for the Helenite when this COVID-19 thing is over?

All this being said, I would absolutely buy helenite in a gift shop. Especially if it came in teal. After all, my inner 9 year old National Geographic-reading nerd is not that far from the surface.

Shiny!

References:

https://www.usgs.gov/faqs/how-much-ash-was-there-may-18-1980-eruption-mount-st-helens?qt-news_science_products=0#qt-news_science_products

https://geology.com/gemstones/helenite/

http://www.geologyin.com/2016/12/worlds-most-amazing-gemstone-found-in.html

https://www.gia.edu/gems-gemology/summer-1986-green-glass-nassau

https://pubs.usgs.gov/gip/msh/ash.html

https://www.pioneerjewelers.com/blue-radiant-bar-earrings-30h

Hometown aquifer, hometown beer!

Some things just go naturally together. Peanut butter and jelly. Christmas and presents. Geologists and beer. Which is why I got so excited when I went shopping for Christmas dinner fixings at the supermarket near my parents’ house and found that a local brewery had released an aquifer-themed beer!

The Memphis Sands aquifer is part of a larger aquifer system that stretches from the Tennessee/Kentucky border all the way to Gulf of Mexico. It contains layers of sand that transmit water and finer-grained sediments that slow its flow, all laid down by versions of the Mississippi River as the ice ages came and went. I was raised on this aquifer’s abundant and tasty contents. So let’s get down to some serious science. How accurate is the can art? And most importantly, how delicious is the beer?

Descriptive text: 7/10

“From deep within the Earth’s crust, the finest drinking water on the planet springs forth to Memphis. This unique aquifer supplies WISEACRE with the most necessary of ingredients for the production of crisp, light-colored lager. The rains that fell to earth 3000 years ago are filtered very slowly through hundreds of feet of fine grain sand, culminating in a huge underground lake filled with 57 trillion gallons of virtually mineral-free water. From this prestigious water reserve, we supply Memphis with Sands, our one-of-a-kind Lager. Beauteous in its simplicity, it is very low in bitterness and full of delicious flavors of bread and crackery malt.”

First and foremost, the description of an aquifer as ” a huge underground lake” is enough to drive hydrologists to grab another beer to drown their sorrows. It messes up people’s mental image of aquifers and leads them to ask me how the fish survive down there. In contrast the “57 trillion gallons” figure for aquifer volume beneath Shelby County is widely accepted, and the 3,000 year age of the water is reasonable. It’s calculated using the slope of units in the aquifer, information we know about the size of grains of sand in the aquifer, and the distance between recharge areas and Memphis wells. (source) This text got 2/3 scientific concepts correct, so I’ll round up and give it a 7/10. Generosity is part of the holiday spirit.

Can Art: 6/10

The artist had fun with this one – the gold “fossil” background and the blue contrast nicely. However, they made the baffling design choice to assign the blue color with watery bubbles to the aquitards (geologic layers that don’t transmit water) instead of the aquifers! This makes no sense! Why not assign the watery blue color to the units that actually transmit water? I could be a Scrooge and critique the fossil background because we don’t really find dinosaur skulls around here, but find the print too cute to complain about it. It gives the can a kind of easily recognized “hey, science!” vibe which appeals to me.

The artist also shrunk down the scale to fit with their placement of the info blurb, rendering it inaccurate. 3,000 feet below the ground surface should really correspond to the bottom of the units layered “Other Cretaceous Units”. An easy fix to make the scale bar fit above the blurb and stay accurate would be to just have it cover less ground – stop at 1,500 feet or so. At least the artist got the names of the units correct. I think the artist based the design on a widely republished diagram from the local chamber of commerce, exhibited below. It also assigns a blue color to the aquitards and a sandy tan color to the sands that make up the aquifers, which may have been what threw the artist for a loop with the color scheme.

from https://www.memphisflyer.com/NewsBlog/archives/2019/12/10/board-pauses-carrier-plan-to-inject-treated-wastewater-into-memphis-sand-aquifer

I think it would be really cool if Wiseacre could tweak this can design to be a little more scientifically accurate. After all the beer-drinking public is much larger than the portion of the public that reads aquifer articles in the local paper. Why not spread some sneaky science exposure on Memphis’ great underground asset to those who crack open an ice-cold can at the end of the day?

Taste: 8/10

This is a great basic lager. I would guess that Wiseacre is aiming this at beer drinkers who would otherwise drink Budweiser and Miller High Life? My dad, my sister, and I split a can as part of an impromptu beer flight. I noticed that the fizziness is a bit unique – it looks flat when I pour it, but the fizz comes to life in my mouth. My sister says it has a bit of a floral and toasty note in the aftertaste. It’s a little bitter, mostly malty, and quite smooth. We didn’t taste a strong hop flavor. We all agree that it’s very drinkable: the kind of six-pack that would be popular at a cookout or camping trip.

In an ideal, non-pandemic world Wiseacre’s tap room on Broad Avenue would be on my must-visit list for my trip back home. I suppose there’s always next year!

P.S.

The aquifer was recently in the news because of a groundbreaking legal case where Mississippi sued Tennessee for “stealing” groundwater. Mississippi argued that the cone of depression caused by Tennessee’s groundwater pumping caused Mississippi’s water to slip away into Tennessee, and wanted $615 million in damages and a halt to pumping. The Supreme Court appointed a Special Master to determine the case, Judge Eugene Siler. Last month he decided that groundwater is a flowing resource, not a static one. Therefore, the water should be distributed as surface water is distributed in the eastern states, by equitable apportionment. Judge Siler’s conclusion is the legal equivalent of locking two misbehaving kids in a room until they sort themselves out. He rejected Mississippi’s appeal for damages and ruled that if the two states find themselves so affected by groundwater pumping, they can apportion the aquifer to determine fair allotments. It only took 14 years – the case was first filed in 2006!

Useful article from the Memphis Flyer: https://www.memphisflyer.com/NewsBlog/archives/2020/11/06/federal-judge-sides-with-tennessee-in-water-rights-case

Shout-out to my thesis advisor’s blog, where he posts an interesting opinion from his colleague on the case: https://www.waterwired.org/2020/11/jjr-ms-v-tn.html

Further Resources:

The defining 2016 article in the local paper that brought awareness of the aquifer to the general public: https://www.commercialappeal.com/story/news/environment/2016/12/16/memphis-sand-aquifer-buried-treasure/93814278/

Dense 1983 US Geological Survey paper on the aquifer: https://pubs.usgs.gov/wri/wrir88-4182/pdf/wrir_88-4182_a.pdf

Wiseacre Brewery! https://wiseacrebrew.com/

Thunder Mountain Lakes Blew My Mind

Note to the reader – this blog post describes a trip to fragile ecosystem via a risky trail. If you decide to follow me here, please use caution and turn up your leave-no-trace skills to 11. 🙂

The third time really is the charm. In June I tried to make it here but the road was still snowed in. In early July I started from a different lower-elevation trailhead, but the pass was…. still snowed in. The snow finally melted in early August – success!

I finally completed this truly magical backpacking trip.

I started from the Hope Lake Trailhead up Tunnel Creek Road off of Highway 2, just a few miles west of Steven’s pass. The Hope Lake trail heads uphill to connect with the Pacific Crest Trail, where I turned south. There’s a rockfall just south of Hope Lake that has a booming and adorable small mammal population – I saw 2 families of marmots and a family of pikas! After the steep first 2.5 miles of the hike the trail flattens out, the trees open up, and all of a sudden you expect Julie Andrews to pop out and start singing the Sound of Music.

The hike from here to Trap Lake is a delightful ramble through wildflower meadows and groves of pine trees.

I got to Trap Lake around noon, claimed a campsite, and made ramen for lunch. And then I started to climb. To get to Thunder Mountain Lakes you head up the PCT to Trap Pass, and then turn south onto a seriously sketchy trail that follows the county line south and up to Thunder Mountain Ridge. Sketchy as in if you slip, you fall 500 feet. Not for the faint of heart, and it could be risky for dogs.

The trail takes you up above the snow line, and starts to be marked with cairns to guide hikers through the snow field and bare granite. There are a few islands of vegetation, including stunted pine trees, pink heather, and blue dwarf lupine. The bees were going wild on the heather – I guess they only have a short window for foraging up here.

At this point I was 6.5 miles from the trailhead and 3,300 feet higher up in elevation. Just as I was having to start counting my paces to keep myself going, I turned a corner and my jaw dropped.

I had made it to Thunder Mountain Lakes! I could see all the way to Mt. Daniel and Hinman Glacier in the distance.

I hiked down to the lake and sprawled on the nice warm granite to eat a chocolate bar. As I got up to look down at the lower lake, I heard a rustle….

… and there was a mountain goat with her fuzzy baby! They’re such lucky creatures, getting to live here full-time. I hung out with them until they made their way along the ridge. The baby kept trying to sprint up onto rocks only to fall – luckily straight into its mom. It takes true love to be your offspring’s bouldering mat.

I lingered up by the lakes until the sun started to sink close to the ridgetop. The nice thing about hiking downhill is that it leaves me with more energy to spare to admire the rocks. The downside of admiring the rocks is that I get distracted and loose the trail. But these rocks were great!

They’re all granite, but conceal a subtle story. Textbook illustrations often depict magma bodies as single lumps that rise and cool neatly independently. Reality, as always, is more messy. Magma bodies (or batholiths, as they’re referred to once they cool down) in reality can merge, or pick up bits of other batholiths, or be reworked once they’ve cooled.

For example, this photo (above) shows a light gray batholith that cracked under pressure once it had cooled. A different kind of magma forced its way through the cracks as it rose, forming the dark grey stripe. Later the line of weakness was reopened and filled with hydrothermal quartz, creating the white streak. It’s kind of like a turducken of igneous rock.

And in this photo, the dark grey magma body ripped up chunks of a paler batholith as it rose and incorporated them into its mix, Pac Man style.

As I headed north back to Trap Pass I got phenomenal views of Glacier Peak as well as glimpses of Mt. Baker to the northwest.

Heading downhill back to my camp I met several fat marmots. Two of them were engaged in a clumsy but effective high-speed chase and high-volume screaming match. Their counterpart above Trap Lake obviously don’t think much of humans and screamed at me to let me know it. (lower left photo)

Trap lake was an idyllic place to spend the night, especially on a Sunday night when most of the weekend backpackers were long gone. I really got a prime campsite (above right) and enjoyed the luxurious packable chair that my sister (the one featured in all the Twin Trek posts on this blog) gave me for our birthday. Glamping all the way!

I spent a leisurely Monday in camp and then headed back to the trailhead at an equally leisurely pace. I really didn’t want to leave. Between snack, scenery, lunch, and pika -appreciation breaks I managed to stretch the 5 miles into 6.5 hours.

I may have had to drive back to civilization that day, but I’m definitely coming back here!

Rampart Ridge Rocks!

At Vanderbilt University’s Wilderness Skills club we classified adventure into two types of fun. Type 1 fun was fun to experience and fun to remember. Type 2, the slightly more common type, was miserable while it happened but either has a great reward or created a story that got you attention at parties.

The hike up to Rachel Lake after work with a 30-pound pack on my back was decidedly Type 2.

Where in the world was I? Trailhead marked in blue, trail in dark green. map created in ArcMap by C. van Stolk using trail shapefiles created by the US Forest Service and ESRI’s Streets basemap.

Trail in bright green – map created in ArcMap by C. van Stolk using trail shapefiles created by the US Forest Service and ESRI’s terrain basemap.

I got off work early on that Friday, headed east on I-90, turned off at the exit for Kachess Lake, bounced up potholed gravel roads to the trailhead, and set out for adventure. I knew the hike went from 2,800 to 4,800 feet in four and a half miles. What I had foolishly overlooked is that it gains 1,400 feet in the last 1.2 miles. A significant distance of that 1.2 miles is literally in a creek bed. It had me questioning my life choices. I had planned to go all the way up to Rampart Lakes at 5,100 feet but I was absolutely done by the time I got to Rachel Lake. I was too cranky to eat my ramen noodles. I set up my tent at the outskirts of an inordinately crowded back country campground just as it got dark, made a cup of tea, and turned in for the night.

The next day was 100% heavenly Type 1 Fun.

I left the burden of my camping stuff where it lay and headed uphill into a clear blue day. My goal was Alta Peak at the northern end of Rampart Ridge, elevation 6,152 feet. I climbed up the ridge past fields of glacier lilies and heather and creeping phlox. It took me about two hours to make it to the top, with views of Mt. Rainier, Mt. Adams, and Glacier Peak. I settled in for an hour with my chair and my map to plan further adventures while I could see so much of the landscape!

Alta Peak, looking south at Mt. Rainier (center) and the Summit at Snoqualmie ski routes (center right).

Alta Peak, looking north (the white tip of Glacier Peak is peeking out from behind the Four Brothers on the center right)

Looking down past the snowdrifts to the basin below Alta Peak

I then rambled downhill to have lunch at Lila Lake. It was hopping with backpackers but I found a nice spot to eat my snack assortment and get yelled at by a marmot.

Once I had my fill of exploring the bouldery outcrops at Lila Lake, I headed south to Rampart Lakes. I spent the rest of the afternoon basking on a rock with a view at the Rampart Lake furthest along the trail. I braved the water for a swim and dried off in the sun while reading a mystery novel and enjoying my sippy flask of rosé. I did not join the hikers who were penguin-sliding down the snowdrift straight into the lake, though.

Rampart Lake, looking up at Rampart Ridge.

Around 6pm I headed back down to Rachel Lake to cook dinner and explore the campsite possibilities in the main campground for next time. I went to sleep in an exponentially better mood than I had the previous night.

Sunday morning I hoped to make it down the horribly steep creek bed part of the trail before the day hikers would be heading up it. Mission successful! I took loads of photos of wildflowers. I set up to finish my novel and eat lunch at a rocky waterfall overlook about a mile from the trailhead.

By this point Friday’s uphill slog was completely a thing of the past. All things considered, the trip had been a delight.

But wait! I couldn’t ignore the cool rocks. You know me.

The rocks exposed up at Rampart Ridge were gray with white clusters of larger elongated crystals. I thought they were really distinctive, but didn’t know their name.

It turns out these rocks have the epic moniker of “glomeroporphyritic basalt”. Glomeroporphyritic translates out of science Latin into “collected-together larger crystals”. In geology-ese, “porphyritic” refers to an igneous rock texture where larger crystals are set in a matrix of rock crystals with a much finer texture, like blueberries in a muffin.

Porphyritic igneous rocks form in two stages – the first one at deep in the earth’s crust, and the second in a shallower, cooler zone at or near the earth’s surface. The large white crystals in Rampart Ridge’s basalt formed when the magma was deep underground. They had plenty of time to slowly cool into large crystals in the hot environment at depth. However, some igneous or tectonic process suddenly shoved the magma body up towards the surface. This made the rest of the magma cool suddenly. Because these newer crystals did not have time to grow, they stayed very small.

But why did this one white mineral form crystals at depth, and not the others?  I turn to a familiar chart from my geology textbooks for the answer. It’s called Bowen’s Reaction Series, and describes the order in which minerals crystallize out of molten rock. This series springs from painstaking experiments involving pulverized minerals, a very very hot oven, and more patience than I possess. They revealed that minerals form into crystals at the different temperatures along a gradient.

Diagram from http://jersey.uoregon.edu/~mstrick/AskGeoMan/geoQuerry32.html

The elemental mix of magma that becomes basalt creates the white mineral calcium plagioclase and the dark gray/black mineral pyroxene, with only trace amounts of other minerals. Calcium feldspar has a higher melting temperature, and so solidifies at a higher temperature while pyroxene has not yet formed into crystals. An important caveat is that not all magma contains all the elements necessary to make every rock in the series, so several minerals may be “skipped” in a certain magma body.

For example, quartz has the lowest melting temperature of all the common minerals, which is why it often forms decorative crystals or veins in the voids left when other minerals have already crystallized.

Quartz veins in volcanic rock higher up on Alta Peak.

The two kinds of rock I saw on this hike date mainly from the Eocene and Oligocene time periods between 55.8 and 23 million years ago. Washington was roughly at it’s current location on the globe back then and the volcanoes of the Cascades were starting to rev up. Since then, these rocks have been folded by tectonic forces, broken by faults, and eroded until they cropped out in the patchwork patterns that geologists map today.

Summarized in MS Paint from the original Snoqualmie Quadrangle Geologic Map by Tabor, Frizzell, Booth, and Waitt of the USGS: https://pubs.usgs.gov/imap/i2538/

The glomeroporphyritic basalt dates from the late Eocene period. It’s colored medium green and marked as Tnbg on the map above.

Tv and the light pink color stands for Oligocene volcanic rocks – an igneous jumble that’s a few million years younger than the glomeroporphyritic basalt. The rocks on Alta Peak are describe in the USGS pamphlet for the Snoqualmie quadrangle as “coarse volcanic breccia and tuff with minor ash flow tuff). They look almost like concrete made with blocky, angular aggregate. Breccia describes rocks created when magma shattered and engulfed surrounding rock as it erupted. Tuff forms when ash becomes cemented by its own heat, like how I described in the Smith Rocks post from 2018. Breccia makes up the ridgeline of the photo below – you can really see how this one rock classification encompasses a bunch of different kinds of rocks that erode differently to create a mix of straight ridge lines and messy talus slopes.

It’s hard to get a sense of the scale of the waterfall in the center from the photo. I could hear it roaring down the rocks from a quarter mile away!

I’m still doing research about how these rock types ended up juxtaposed. Western Washington’s rocks tell a complex story of bits of foreign continents (called accreted terranes) that were stuck onto the rest of North America by subducting plates, then covered with volcanic rocks and shuffled around by faults. It’s the northern relative to the process in Southern Oregon that I wrote about in my accreted terranes post. Up here, the terranes were even more altered by volcanism and faulting.

It definitely created a fantastic landscape!

Volcanic breccia on Alta Peak

Resources:

Definition of glomeroporphyritic basalt: https://blogs.agu.org/georneys/2011/07/14/geology-word-of-the-week-g-is-for-glomeroporphyritic/

USGS map and pamphlet for the Snoqualmie Quadrangle: https://pubs.usgs.gov/imap/i2538/

Info on volcanic breccia: https://en.wikipedia.org/wiki/Breccia#Volcanic

Information on Bowen’s reaction series: https://courses.lumenlearning.com/physicalgeology/chapter/3-3-crystallization-of-magma/

 

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.

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.

Resources:

https://en.wikipedia.org/wiki/Newgrange

https://www.ancient.eu/Newgrange/

Granodiorite at the Mourne Mountains: http://www.mournelive.com/how-the-mournes-were-formed.htm

Gabbro on the Cooley Peninsula: http://www.3roc.net/assets/CooleyPeninsulageology.pdf

 

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.

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.

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.

Illustration of a basalt flow interior with vesicular zones, entablature, and colonnade from: https://jgs.lyellcollection.org/content/157/4/715

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.

Image from: http://homepage.usask.ca/~mjr347/prog/geoe118/geoe118.054.htm

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.

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

Resources:

https://www.geolsoc.org.uk/GeositesGiantsCauseway

booklet on the geology of Northern Ireland’s Coast: http://ccght.org/wp-content/uploads/2012/05/geology_booklet.pdf

A field trip at the Sand Atlas blog whose author took some better photos of the formations: https://www.sandatlas.org/giants-causeway/

Debbie Hanneman over at GeoPostings did this trip back in 2017 and shared some great photos: https://www.geopostings.com/category/giants-causeway/

AGU resource on columnar jointing: https://blogs.agu.org/georneys/2012/11/18/geology-word-of-the-week-c-is-for-columnar-jointing/

Information about the geology at Carrick-A-Rede: http://www.habitas.org.uk/escr/site.asp?item=1145

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, http://www.jstor.org/stable/30078348. Accessed 14 May 2020.

Cool podcast about the tiny creatures that become chalk, courtesy of Radiolab: https://www.wnycstudios.org/podcasts/radiolab/articles/190284-war-we-need