I’m going to be a Beaver!

I promise that I haven’t forgotten about the blog. This summer has been crazy for multiple reasons, but most importantly because I’m preparing to move to Corvallis, Oregon in the end of August.

I’m starting a master’s program in geography to study groundwater resource management at Oregon State University!

Image result for oregon state university

The downside of the move is that my budget for out-of-town summer camping trips to see new rocks has been displaced by a budget for a Uhaul rental, Ikea furniture, and other elements of a 2,362 mile move.

The upside about this is that I get to take a 5-day cross-country road trip with my father, through some of the most amazing landscapes in the USA! Which should give me enough blog material for a long string of posts. My mother and sister, who both have experience driving cross-country with me to and from California, have already informed him that it’s best for our health and safety if he drives through the geologically interesting bits. Kansas, however, will be all mine…



Petit Jean State Park: the nerdy perspective

To minimize my off-topic rambling, I’m covering my trip to Petit Jean State Park in two posts: Petit Jean State Park: the outdoorsy view about the hiking, and this one to cover the geology we saw along the way! This second post one may make more sense if you read the first one before it.

“So in the beginning there were the Ninja Turtles, and then the extra Ninja Turtles, and then the volcano erupted and BAM! They got stuck!” That hypothesis spilling out of the mouth of the Boy Scout behind me on the trail seemed like a pretty logical idea actually, given that we were staring at a rocky meadow filled with fractured stone domes the size of small cars.


Let’s zoom back out for a moment.  We need some perspective to see what these turtles are made of, where they are, and why they’ve been able to hang around.

Geologically, Petit Jean State Park lies in the Arkansas Valley region of the state, sandwiched in between the faulted, tortuously folded rocks of the Ouachita Mountains to the south and the flat pile of sedimentary rocks that form the Ozark Plateau.

Arkansas geologic regions

Geologic regions of Arkansas – the park location is mark with a star. Yellow colors indicate unconsolidated sediment, greys and blues are conglomerates and igneous rocks, light green is sandstone, darker green is shale, and blue is limestone.

Because of this pressure from the south, the layers of sedimentary rock around the park are gently folded into shallow syncline ( U-shaped) and anticline (n-shaped) structures. The axis of these folds is perpendicular to the source of pressure, so the folds create east-west trending lines on the surface. Closer to the Ouachita Mountains the pressure exceeded the rocks’ ability to deform into folds; they broke along faults, like the Ross Creek faults on the right-hand side of the image below.

petit jean cross-section 2

Information taken from the Arkansas Geological Survey maps for the Atkins and Adona Quadrangles

The Pontoon Syncline creates the bowl-shaped plateau that the park rests in. From above, the plateau looks like the head of a bird overlooking the Arkansas River.

Petit Jean Mountain Bird

I couldn’t resist messing with the USGS topos…

This topography closely mirrors the underlying geology of the park, showing where the Arkansas River and Rose Creek have broken through the tough sandstone “cap” of the plateau. (Arkansas Geological Survey map of this view can be found here)

Petit Jean specific geologic map crop

The geologic map for the Adona Quandrangle below covers the southern part of the park, and highlights the trails that Jackie and I explored. In the zoomed-in box, you can easily see how Cedar Creek is carving back into the resistant Hartshorne sandstone that caps the plateau to expose the weaker Upper Atokan shale below. Click on this sentence to go to the Adona quadrangle map PDF courtesy of the Arkansas Geological Survey.

Detailed geology of Petit Jean

Nowhere in the park is the stratigraphy more defined than at Cedar Falls! There’s a clear boundary visible between the pale sandstone at the top of the falls and the darker shale at the bottom.




Up-close and personal with the contact between the Hartshorne sandstone and Atokan shale

During the early Pennsylvanian period when these sediments that would become these sandstone and shale rocks were deposited, central Arkansas was submerged under a shallow continental sea. The Atokan shale and Hartshorne sandstone are separated by an eroded gap in the record that erased years of sediments – an unconformity. Their composition tells a story of a changing depositional environment: it was in a coastal swamp or underwater and filled in with fine-grained muds from around 315 to 311 million years ago (mya), ended up above water either by uplift or a dropping sea level around 311 mya, and the re-covered by a blanket of sand deposited by meandering river systems and deltas from approximately 311 mya to 307 mya.

The sandstones and shales in this park are about 10 million years younger than the similar rocks I’ve profiled in Giant City State Park (Illinois Basin), and about the same age as those  I climbed on in the Red River Gorge area (Cumberland Plateau).  They all belong to the Carboniferous period from 299 to 359.2 million years ago.

NA early pennsylvanian crop annotated

Background paleogeographical of the Early Pennsylvanian Period map copyright of Colorado Plateau Geosystems.

The Carboniferous period is defined by huge jungles of ferns and early trees that flourished in the high oxygen levels, and then were buried to for the coal that now powers our industrialized lives (Carboniferous = Latin for “coal bearing!). You can’t find coal in Petit Jean State Park, but a few fossil traces of this era remain! The best-known fossil location in the park, along the Cedar Creek trail, was covered by an intermittent stream when we were there but signs along the Cedar Fall Overlook boardwalk also give visitors an introduction to the first drafts of trees that once grew here.


Beside the fantastic views from the top of the plateau, there are two smaller-scale geologic features that make this park awesome to explore: the “carpet rocks” and those “turtle rocks”!


Like sandstone rocks in the other two parks, the Hartshorne sandstone contains the dark, wavy, resistant iron formations called Liesegang banding. Unlike the other parks, though, Petit Jean sits on the northernmost fringe of rocks deformed by the rising Ouachita Mountains between 290 and 245 million years ago.  This pressure created geometric series of cracks in the sandstone, and when water enriched by tiny iron-rich hematite, goethite, and magnetite particles entered these cracks it left behind a cement stronger than the surrounding rock. As the weaker rocks are the iron-rich cement was worn away, it left behind the crazy raised pattern of the carpet rocks. Unfortunately the best examples were underwater when I visited the park, but here’s a photo from the Arkansas Geology website:

carpet rocks

You can also see subtler version of them in the cliffs in the first 1.5 “map miles” on the Seven Hollows trail (eastern part of the trail).


The most striking geological feature of this park isn’t found anywhere else – the turtle rocks! No real (or Ninja) turtles were harmed in their formation. The Arkansas Geological Survey blog describes them as:

“unique, mounded polygonal structures that resemble turtle shells.

The processes that generate “turtle rocks” are not clearly understood. One explanation suggests that these features were created by a process known as spheroidal weathering, a form of chemical weathering that occurs when water percolates through the rock and between individual sand grains. These grains loosen and separate from the rock, especially along corners and edges where the most surface area is exposed, which widens the rock’s natural fractures creating a rounded, turtle-like shape.

Additionally, iron is leached from the rock and precipitated at the surface creating a weathering rind known as case hardening. These two processes along with the polygonal joint pattern contribute to this weathering phenomenon.”



These turtles rocks exist at the very top of the plateau, and at the top of the ridges.  This is different than at similar sandstone “caps” on the landscape in temperate regions, like in the Red River Gorge, where the top of the formation is relatively smooth and even. Water is relentless in finding the most efficient path downhill and these turtle rocks, with their crazy honeycomb drainage pattern, defy shortcuts. My idea is that the turtle rocks only exist at the top of the because of the nature of stream drainage patterns, stream flow, and the speed of that flow.

It’s pretty intuitive that intermittently wet ditches feed into into small creeks, which flow into medium-sized streams, which combine to form rivers. On the quantitative side of hydrology this is represent by the “stream order” systems classified as 1, 2, 3…. where order 1 streams have no regular tributaries, order 2 streams have 1 tributary, etc. By definition, in a given watershed order 1 streams are at a higher elevation that order 2 streams (there’s no cheating gravity!), and the stream order increases with decreasing elevation.  By the the time water organizes itself into something that a hydrologist would give an order number it has carved out a regular depression in the terrain that it reliably flows through.

Reliable flow, though, would be lethal for a turtle rock. They only exist because the force of water can’t yet overwhelm the intrinsic weirdness of their structure. A little water emphasizes the shape of the rocks by removing small amounts of sand slowly enough that it doesn’t erase the maze of fractures and cracks that define the turtles’ shells. Because of this, they can only remain at elevations above the highest order 1 stream, where rainwater hasn’t organized itself into defined channels yet.

However they were formed, they give the landscape a surreal Dr. Seuss-ish touch that’s really delightful. And just down the trail from the turtles, there’s a patch of tafoni “honeycomb” weathering interspersed with Liesegang bands that reminds me of a village in “All the Places You’ll Go!”. I know it’s made by pockets of easily dissolved minerals like salt or chalked weathering out of harder sandstone and ancient iron deposits, but my inner eight-year-old sees a miniature cliff dwelling…


Petit Jean State Park crams so many whimsical rock formations, fossils, and cliff-top views into a relatively small piece of land. It makes for a wonderful field trip!

For more information on the park’s unique geology, check out:

“The Geologic Story of Petit Jean State Park”, a field guide written by Angela Chandler

The entry for Petit Jean Mountain on the Encyclopedia of Arkansas



Petit Jean State Park: the outdoorsy view

To minimize my off-topic rambling, I’m covering my trip to Petit Jean State Park in two posts: this one about the hiking, and Petit Jean State Park: the nerdy perspective to cover the geology we saw along the way!

My friend Jackie and I had been trying to put together a camping getaway for a few weeks. On the recommendation of Jackie’s friends, we finally made the commitment and the three-hour drive to head west to Petit Jean SP, near Morrilton, Arkansas. It’s hard to tell from the campsite map but Jackie and I both would recommend camping in the secluded, shady Loop C and Loop D campsites over the wide open Loop A and B sites. Not that we could tell when we finally made it to the park at 11 pm.

Walking along the paths of Petit Jean State Park feels like someone took all the most gorgeous parts of four or five similarly sized parks and spliced them together into a highlights reel. Around every corner there’s a jaw-dropping view, a waterfall, a thundering 90-foot waterfall, a rock shelter, or an adorable little brook, and every patch of turtle rocks is more turtle-y than the last.  Jackie and I thought her friends were exaggerating as they described it but they sure weren’t!

You can find a full map of the trails here and of the campsites here on the park website. I went crazy in MS Paint to create the version below:

Petit Jean Annotated trail map

Petit Jean State Park has the distinction of being the first state park in Arkansas, founded in 1923 and endowed with lodges and trails by the work of the Civilian Conservation Corps during the Depression. On Saturday the two of us linked five of those trails in the park into an 8-mile loop.


Jackie playing with her new camera’s settings at the overlook at the trailhead behind Mather Lodge

We started down the Cedar Falls trail early in the morning, hoping to beat the crowds. Several families were already heading downhill, and we ran into my next-door neighbors too. Small world! The trail is rocky but obviously the Civilian Conservation Corps put a lot of hard work into it – the path has dozens of rock steps. It’s beautiful too, as it follows a rocky little creek.


Cedar Falls was worth every bit of the hype. Torrential rains on the Thursday and early Friday before we arrived meant that the falls were flowing at full blast! Look for the people in the photo below for scale…



By the time we left the falls at 10:30, we felt like salmon struggling upstream as we squeezed past a solid line of families bound for the waterfall. Back at the bridge, instead of heading back up to the trail head we took the Cedar Canyon trail west. A few hundred feet past the intersection with the Cedar Falls trail we might have been in our own personal jungle – not another person in sight! This shady trail follows the creek down the valley, with some beautiful views of the flowing water, giant fallen boulders from the cliffs, and lizards hanging out on the rocks. Definitely wear long pants if you want to hike this one – the poison ivy was lush and thriving, but so were the wildflowers. We stopped at a convenient flat rock by the stream to have lunch, which we shared with a flock of very small blue butterflies.


blue flowers

(Jackie’s photo)


Technically, the Cedar Canyon trail dead-ends into the Boy Scout Trail at a sturdy set of stepping stones across the creek. However the massive rainstorms on Thursday and Friday which made the waterfalls so spectacular also raised the creek above the level of the stepping stones. So we got wet. The water was freezing cold and actually pretty refreshing in the noonday heat.


The Boy Scout trail from the stream back up to the road is steeply uphill and an excellent leg workout. On one of our breaks to get some air back into our lungs, we met this little green tree frog taking a siesta!


Jackie’s new camera is amazing for close-ups!!

The Seven Hollows trail is a dangerous place to go with a photographer and a rock-climbing geologist. The trail map said it was a 2 to 4 hour hike– we spent almost 6 on it. We hiked it backwards according the the trail map (counter-clockwise), which turned out to be perfect timing. Most of the families and other hikers we passed hiking to Cedar Falls did that trail as an out-and-back and then drove to the Seven Hollows trailhead to hike it clockwise after lunch. In the first mile of the trail we passed several exhausted-looking groups, and then we pretty much had our own personal trail! That first bit of our hike on that trail (Map miles 4 to 3) descended into one of the seven hollows the trail is named after – 50-foot cliffs rose on either side of the trail, full of hidden caves and swallow nests. It was so peaceful with the burbling stream at our feet and the birds singing. Not to mention, that mile is all downhill.

After “map mile” 3, the trail started to rise into the pine trees and sandstone clearings on top of the ridge. Jackie was so patient with me, because I’m the kind of person who wants to climb every boulder that I safely can, and there was no shortage of boulders.

The one downside of this trail is that it easily becomes a stream in wet weather like we had in the days before our trip, and especially from our “backwards” perspective the path that looks the nicest may actually be incorrect. Jackie and I spent an idyllic (and flat) ten minutes strolling down what turned out to be a trail to private property before noticing the absence of blue blazes. We retraced our steps to discover we should have taken the left-hand fork: the nearly vertical, soaking wet, bare rock face that was actually the trail. Oops.

That slippery slope is totally worth it, though because it leads to the highlight of this section of the trail: The Grotto. You reach it via a narrow, rocky spur off of the main trail that opens up into a rock shelter and cascade that look like a scene straight out of The Land Before Time.


I took a side trail up above the falls, and found a whole herd of turtle rocks!


After the Grotto, the trail turns back uphill has we climbed up the last ridge that the trail crosses before heading north to the trailhead. The peak of this part of the trail has more sandstone clearings and beautiful views to the southeast.

Jackie and I were in a hurry, though, to reach the last big landmark of the hike – a natural bridge. It lived up to the expectations! We hung out there for a while, refueling with trail mix and exploring all the nearby rock formations. For more on how arches like this are formed, you can check out my Red River Gorge post here. Same process, different sandstone!


can i climb it full view

Contemplating whether I was feeling rash enough to free-solo my way up to the top of the cliff by the arch. I decided I wasn’t. It was SO tempting though.

There aren’t any more landmarks noted on the park map after the natural bridge, but if you keep your eye out there are two caves in the sandstone cliff on between the bridge and the trail head. After the two caves, at about “map mile” 0.5, there’s a well-beaten path that appears to dead-end in a cliff wall. If you take a sharp left at the “dead-end” and are comfortable scaling a short 5.4 climb, there are some spectacular turtle rocks up top and you can see for miles. The golden late-afternoon light and our haze of exhaustion made it really seem magical. Jackie and  obviously need to hike more often so 7 miles doesn’t turn our legs to jelly.



The only downside of the Seven Hollows trail is that it ends in a long uphill climb whichever direction you do it in.  Another mile up the trail we basked for a while in the evening sun, like two very tired lizards, on top of the rock formations at Bear Cave before making the last 1/2 mile push to the end.


^ The view from the top of the Bear Cave area, and Jackie climbing down

We celebrated with soda and junk food at Mather Lodge around 7pm and then drove back to Bear Cave for a great tour of the area with interpreter BT Jones and 53 other visitors. It was definitely worth it to hear the stories of the pioneer days of the area and to make a giant echo off of the walls of Cedar Creek Canyon.

We slept very well that night, and threw out the pipe dream of waking up to see the sunrise. We got up just early enough to pack up camp and start the Cedar Creek loop trail bright and early at 8 AM, when we had it all to ourselves! This trail is has a brochure that indicates that it’s a self guided tour (you can find it here), but Jackie and I couldn’t find stops 3, 4, or 5. The entire trail look like Middle Earth in the early morning light, it was really magical.


Jackie at a beautiful place for a snack break


The leaning rock along the Cedar Creek trail


Textbook-perfect ripple marks in the sandstone on the southern leg of the trail

After lingering on this loop for an hour and a half, we piled back into the car for a driving tour around the overlooks in the park.


Jackie at the Cedar Falls Overlook. Not only is it beautiful but it’s handicap accessible too.


At the M.A. Richter Memorial Overlook you can see all the way to Mount Magazine, the highest point in Arkansas, 50 miles away!


Jackie enjoying the view at the CCC Overlook


The CCC shelter at the CCC Overlook – there’s a lawn to the right of it that would make an absolutely perfect picnic spot.

We had one last hiking stop – the trail down to the Rock Cave archaeological site. It winds through a phenomenal field of turtle rocks…


There must have been dozens of them!

exploring the rock house

You could easily fit a football field inside this rock shelter, no joke. (Jackie’s photo)


One of the several Native American paintings in the shelter, drawn with red iron oxide paint over 500 years ago.

Jackie and I had one last stop as we headed out of the park: Stout’s Point and Petit Jean’s gravesite.

The name of Petit Jean Mountain and its park have a sweet and possibly even true backstory. The area was first explored by French traders, and the story goes that one of these traders had a particularly devoted sweetheart. Unbeknownst to him, who would have forbidden her to come if he knew, she sneaked onto his ship in the guise of the cabin boy “Petit Jean”. Her disguise held up and she was able to at least be close to him until the story took a tragic turn as they headed up the Arkansas river. She came down with a sudden illness, and only as she was dying did those caring for her discover her secret. Her last wish was to be buried on top of the magnificent lookout she saw from the river, and her grieving trader carried it out.

That lookout is now called Stout’s Point, after the Episcopal minister who led the effort to settle the mountain with white pioneers.

view from stout's point

The view of the Arkansas River from Stout’s Point


Jackie and I didn’t want to leave the park – we agreed that we needed a break in the space-time continuum to add another day to the weekend. Unfortunately we had to face reality and head back east, but now Petit Jean State Park has two more passionate promoters!

CCC overlook both of us

All of Jackie’s photos are cc Jacqueline Arevalo

A Tale of Two Sandstones: Giant City State Park

Earlier this month I found myself driving though the hills of southern Illinois, and decided to take an extra time to spend some quality time with the topographic relief and exposed rock that us residents of western Tennessee don’t see very often.  I spent the morning rambling though Giant City State Park south of Carbondale, and didn’t want to leave! I wandered around the Giant City Nature Trail, which is only officially 1.5 miles but probably more like 3 if you take all the side-trails. After that I stopped by the short Devil’s Standtable trail on a whim, and I’m glad I did! It follows the base of a gorgeous cliff line, and has ample opportunities for scrambling and climbing.


This strategically place trail sign with geologic information might dissuade you from exploring further, but take the well-traveled unofficial trail past it to get to a waterfall!

Southern Illinois is a island of rugged terrain in a state where the elevation rarely exceeds “rolling hills”. It barely managed to escape the Wisconsonian glaciation which bulldozed Illinois north of Highway 13, creating prime cornfield habitat north of the highway and a maze of deep valleys, tall sandstone cliffs, and forested ridges south of Carbondale and Harrisburg. All in all, this section feels more like a misplaced chunk of the Ozarks.

It occurred to me, while eating my lunch on top of a stray sandstone boulder, that the landscape look like a miniature version of the Cumberland Plateau 300 miles to the east. (You can see where those rocks come from in my Red River Gorge Post) These sandstone outcrops had the same iron bands, fragmented blocky weathering structure, and selection of trees clinging tightly to their cliffs. This made me wonder – are these rocks part of the same depositional unit as the ones on the Cumberland Plateau, or do they have a different source but just happen to look similar?


A particularly enterprising tree along the Giant City Nature Trail

Callan Bentley did a great breakdown of the geologic features of the sandstone of the park over at the AGU blog. It turns out that the lacy weathering structure that I had been calling “honeycomb” has the snazzy official name of “tafoni”! I don’t think I can beat Callan’s beautiful photographs and blow-by-blow of depositional features, but I couldn’t find a source for my origins question and set out to research it.

It turns out that the rocks I was admiring, clambering on, and using as a picnic bench were part of the Chesterian formation of sedimentary rocks laid down during the second half of the Mississippian period roughly 359 to 323 million years ago. Therefore, they’re roughly the same age as the rocks on the Cumberland Plateau which were laid down during the Carboniferous era (which is divided the Mississippian period followed by the Pennsylvanian Period).

The rocks in Giant City State Park are on the western edge of what’s called the Illinois Basin, a regional depression in the crust exacerbated by large amounts of sediment deposited when the region was covered by a shallow sea until the Late Pennsylvanian period ~300 million years ago. This same sea also covered the area now occupied by the Cumberland Plateau, and its waves crashed against the shores of the vast deltas carrying sediment down from the rising Acadian orogen of the current Appalachian mountains. The rocks in the Red River Gorge of eastern Kentucky aren’t in the same “family” as the rocks in Giant City State Park, in the sense that they don’t share a sediment source, but instead are classmates from different origins maturing together through geologic time.

There was a bit of a speed bump that separated the Illinois Basin from the Appalachian Basin – the Cincinnati Arch. Now, as we get acquainted with this speed bump, there’s something to keep in mind. Although the older Ordovician rocks at its core might indicate that it’s an anticline (a convex fold in sedimentary layers), this cross section has a trick up its sleeve.


This diagram shows a vertically exaggerated cross-section of the types of bedrock in Kentucky, show that the rocks of the Appalachian Basin (Cumberland Plateau) are separated from the rocks of similar age in western KY/Southern IL by the Cincinnati Arch.

The Cincinnati Arch isn’t a fold structure, but a strip of crust that maintained its original elevation  while the regions to the east and west sagged under the weight of sediment that was piling onto them. I couldn’t find primary resources resource to mention why exactly the Cincinnati arch was able to avoid being down-warped by sediments as its eastern and western neighbors were, unfortunately. (If you know more about that, please contact me!)

That cross-section sparked my interest, so I set out to find a paleogeographic map of North America during the Mississippian period when the Illinois Basin and Cumberland Plateau sandstones were being dumped into place. This map shows a reconstruction of the Early Mississippian, so sea levels would have been a bit lower in the mid- to late- Mississippian period when the Chesterian rocks were laid down.  About 1/3 to 1/2 of northern Illinois would have been above the waves.  I fancied it up in CorelDraw to show the arch, basins, and approximate directions of sediment transport into the basins…

Annotated Mississippian Map 4

Looking at the map, you notice that the arrows pointed to the Appalachian basin come from a mountainous region, and the ones pointing towards Illinois come from part of the land surface that’s relatively flat. This is reflected in the depth of sediment with each basin – the sandstone layers in Illinois are thinner than those in eastern Kentucky. Conversely, because the Illinois basin contained a slightly deeper sea with less sediment input it has thicker layers of limestone in the Carboniferous deposits than the Appalachian basin.

The limestone of the Illinois basin is a major economic resource in the area. Driving down Highway 51 leaving the park (sigh…) I passed the Anna Quarry Company, which has been profiting from that ancient Carboniferous sea since 1865. Their 200-acre, 450-foot deep original mining pit was abandoned when it became economically unfeasable (let’s just say, it now has 350 feet of water in it) but they continue to mine new pits on the property to provide raw materials for aggregate, asphalt, concrete, and agricultural lime.


I got some really funny looks as I parked along the highway to take photos…

Anna Quarry

An aerial view of the Anna Quarry in Anna, Illinois

It was a beautiful sunny drive back to Memphis, but I need to drag some friends back to Jackson Falls in this same area to climb soon!


Giant City State Park website: https://www.dnr.illinois.gov/Parks/Pages/GiantCity.aspx

breakdown of geological formations: http://blogs.agu.org/mountainbeltway/2011/09/20/giant-city/

Chesterian sandstone, which includes the rock at the park: http://isgs.illinois.edu/ilstrat/index.php/Chesterian_Series

A retro but generally accurate backstory of the geology of southern Illinois: https://www.ideals.illinois.edu/handle/2142/42765

A more approachable take on the ancient landscapes of Illinonis: https://www.isgs.illinois.edu/outreach/geology-resources/build-illinois-last-500-million-years

Source of KY cross section: https://www.uky.edu/KGS/geoky/beneath.htm

Source of paleogeographic Mississippian map: http://deeptimemaps.com/wp-content/uploads/2016/05/NAM_key-345Ma_EMiss.png

Source for information on Cincinnati Arch: http://ncad.net/Gp/Erla/ErlaGeol.htm

Blog post about Cincinnati Arch: http://historyoftheearthcalendar.blogspot.com/2014/03/march-10-cincinnati-arch.html

Bedrock Geology of Illinois Map: http://isgs.illinois.edu/sites/isgs/files/maps/statewide/imap14-front.pdf

Bedrock Geology of Illinois Strategraphic Sequence: http://isgs.illinois.edu/sites/isgs/files/maps/statewide/imap14-back.pdf



Happy Birthday, GRACE!

NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites had their 15th birthday this week! The mission was only meant to last 5 years, but dynamic duo of earth-monitoring satellites has kept on observing gravitational anomalies from orbit since they were launched on March 16, 2002. NASA put out this graphic to celebrate:

GRACE satellite

So why do we care about gravity enough to collaborate with German’s space agency (GPZ) to spend 127 million dollars to launch a payload into space to measure it more precisely?

  1. If this gravity tugs Grace 1 and Grace 2 out of the perfect elliptical orbit, it can do so with the very sensitive GPS satellites. This gravity data allows us to re-calibrate GPS data to take minute variations in satellite orbit into account.
  2. We can measure inch by inch the slow upwelling of the mantle as the continents rebound after the last ice age.
  3. Satellites calibrate elevation data by assuming that the height of the ocean surface is essentially spherical, but gravitational anomalies (subduction trenches, mid-ocean ridges) can locally affect sea level. Previous satellite missions such as JASON and TOPEX/POSEIDON very precisely measured the distance from orbit to the sea surface but prior to GRACE, trying to figure out ocean current patterns was like trying to guess the the thickness of hair on someones’ head when the person had a bizarre bouffant hairstyle and we had only vague ideas of what the head underneath was shaped like.
  4. My favorite reason – we can track changes in ice caps and water resources such as melting or accumulating ice, floods, and groundwater recharge or withdrawal!

The two GRACE satellites (GRACE-1 and GRACE-2) are roughly the size of two large couches, and are in constant contact via a laser beam which continuously measures the distance between them. If one of the two flies over an area with a large gravitational anomaly it slows down, which either increases or decreases the distance between the two depending on whether the lead or following satellite is slowing down. This distance data is then compared with GPS information of the two satellites that is collected at the same time to create a “geoid” – a vertically exaggerated model of the imaginary topographical surface of the earth where areas with higher gravitational pulls have a high elevation, and the opposite for areas with lower gravitational pulls.


Earth's gravity field as seen by GRACE

Simulation of the geoid, courtesy of NASA Earth Observatory

The image above come from https://earthobservatory.nasa.gov/Features/GRACE/page3.php, which also does a much  better job of describing GRACE and the geoid than I can. When this data is combined with data from other satellites and ground-based systems, it has the illustrious scientific name of the “Potsdam Gravity Potato“, based on the city in Germany where a research team specializes in this melting pot of remote-sensing data.


The 2011 Gravity Potato – but does it taste good with butter and parmesan cheese?


The magic of the GRACE data comes in its 15 years of data. In that time period certain features on the geoid are almost stationary (The Himalayan mountain range, the depression around Hudson Bay where the Laurentide ice sheet depressed the earth’s surface). However, water is heavy and constantly moving, and these satellites give us a quantitative idea of exactly how much mass is shifting (i.e. being melted or withdrawn) without having to deploy squads of intrepid graduate students to take GPS elevation readings all across Greenland.

The University of Colorado –  Boulder created an online platform to explore the GRACE data – click HERE.

GRACE CU Boulder portal

GRACE’s ability to monitor change also gives us an unprecedented look at the invisible water we rely on – groundwater! While we still don’t have a way to take an MRI of the earth a determine the volume of water in an aquifer, GRACE can at least note when an area becomes relatively heavier (aquifer is recharged by rain or snowmelt) or lighter (aquifer is pumped, and the water flows away through rivers to the ocean). Calculating the rate of this change allows us to discover which aquifer systems are declining at rates that could endanger future use.

UC Irvine groundwater storage trends from NASA's GRACE (2003-2013) for Earth's 37 largest aquifers.

Image from the 2015 study by Richey et al. 2015, courtesy of NASA Jet Propulsion Lab

The world map above shows 37 of the most critical aquifer systems humans depend on, and whether their amounts of water in storage have increased or decreased between 2003 and 2015. (For more information click HERE) Decreases are shown in varying shades of red and orange (as in California’s central valley, or northern India), and increases are shown in shades of blue (High Plains aquifer, Murray-Darling Basin). Before GRACE, the only way to approximate this information would be to check hundreds of wells around an aquifer every single month! Compared to the resources needed to drill thousands of wells and employ scores of technicians, $127 million to launch some satellites seems like a steal.


The above map shows a more general view of terrestrial mass change from GRACE data between 2003 and 2009, and was quoted in this article by Dr. Mohammad Shamsudduha, (Institute for Risk and Disaster Reduction, University College London, UK) about groundwater drawdown in northern India, for example.

The dilemma of being a scientist is that the “OMG isn’t it fantastic that we can get all this data to learn about the earth!!” feeling is countered by the “Well darn this data gives us terrible news” feeling. The upside is that the GRACE mission, for the first time, gives us accurate month-by-month information on the state of our ice caps and aquifers. If nothing else this gives scientists a powerful tool to understand natural seasonal variations and tease out man-made changes. If we can’t measure a phenomenon, we can’t accurately improve our reaction to it. I hope that through this data scientists can show policy-makers how we’ve caught ourselves red-handed draining the earth’s accessible water stockpiles, and incite action to preserve what is left.

I was geeking out about these satellites to my sister, who immediately had the same mental image – I just had open up MS Paint to draw GRACE-1 and Grace-2 wearing fluffy, sparkling quinceneara dresses in honor of their 15th birthday. See below for the delightfully ridiculous result.

Satellites in quinceneara dresses

P.S. For more of the nuts-and-bolts mathematical and engineering behind how these satellites work, you can check out this informative circa-2003 internet flashback.

P.P.S. for even more information, check out these links!


CU Boulder geoid team – http://geoid.colorado.edu/grace/about.html



Discovering Geographical Information Systems: Quantum GIS

I had gotten frustrated with creating site maps in AutoCad 12 LT, and yesterday’s field work was postponed because of rain. Additionally, Quantum GIS software is free. This turned out to be a great combination.

Not to bash AutoCAD 12 LT (for non-technical readers – AutoCAD LT is the “Lite” version of a common engineering drafting software program)- it’s been great for creating site maps for industrial clients who can send me their base plans already in AutoCAD format. I add some new layers for their hazardous waste locations and protocols, drop it into my company’s standard frame, and voila. However, I was going back to my company’s decade-old protocol for mapping monitoring wells in AutoCAD and found it cumbersome. In order to make an accurate map I had to take a screenshot of Google Earth, save it, attach it as an external reference file, adjust the raster DPI so it didn’t look like an 8-bit video game, and then set the layer properties so it wouldn’t accidentally be moved while I added feature points. With that done, I had to go back to Google Earth and transfer a scale – and good luck if I had zoomed the map to fit the site boundaries while in AutoCAD. Once the well locations and site outlines were traced, I would delete the base map. I figured that there had to be a simpler way to do this.

I got the decisive nudge towards exploring Quantum GIS from a geologist friend whose specialty is managing complicated Oracle/ESRI ArcGIS systems.   We were having our usual nerdy kind of conversation over dinner on Friday (planetary plausibility of Star Trek, using radar to map the subsurface of Mars, oil pipelines, etc) when I brought up my mapping conundrum. I had been using the free version of Google Earth Pro but it lacked some of the features I wanted, and he suggested QGIS as the next step up.

Quantum GIS (QGIS) can be downloaded here.

I will freely admit that even though I had done some basic cartography in ArcGIS a few years back, I had little idea what to do next. QGIS has a graphical interface comparable to AutoCAD LT, actually – helpful enough but not completely intuitive. Luckily, there’s an instruction video for pretty much everything on YouTube.


Klas Karlsson created a clear, concise, and useful walk-through of a basic project – you can find it here.

Next I wanted to find a general overview of what the software could do – which“A Gentle Introduction to GIS” by T. Sutton, O. Dassau, and M. Sutton of the Department of Land Affairs of South Africa does nicely. This free text serves as an introduction to geographical information systems in general, but focuses on QGIS. It does a good job of making the software less intimidating, answered my questions about the cartography projections I had to choose between,  and gave me a basic view of the analytical capabilities I can learn in the future.

So, to compare map outcomes (…drumroll…):

Estimated water table surface map made with AutoCAD 12 LT:


Versus a map of the same site made with QGIS (client data blurred out):


This landfill in West Tennessee hasn’t had any contamination in the years my employer has been sampling here – good for the planet and keeping my job simple!

For now I drafted the water surface elevation contours and flow direction by hand and then digitized them, as my company has done in the past. However, I know that somewhere in the jungle of optional plugins there’s a way to make QGIS create groundwater contours based on my data points. That’s going to take more than an afternoon’s study to master though, and I look forward to getting to that point!

UPDATE 6/1/2017: the “contour” plugin is really easy to use. Luckily my hand-drafted curves weren’t too terribly off from the calculated curves. The figure below shows the calculated curves in brown.

QGIS contour comparison redacted

Advantages to AutoCAD LT:

  • Ability to draw splines/curved lines, easily rotate shapes and text
  • Faster rendering time between zoom frames
  • Option for typed commands instead of click-and-select
  • Format is widely used across engineering and environmental consulting fields

Advantages to Quantum GIS:

  • Base maps are so easy to insert, delete, and switch out!
  • Ease of entering attribute data, and ability to make any variable of that attribute data a visible tag on a feature location
  • Can enter well locations based on the coordinates measured in the field
  • Easy to measure distances
  • Instant scale
  • Instant and easily modified legend
  • Spatial analysis, once I figure out how to use it
  • FREE

After this intro I’m hooked on the possibilities of QGIS. I’m seriously tempted to digitize my hand-sketched field camp maps and start using it for my Phase I Environmental Site Assessment maps…

I definitely have enough left to learn to fill many a rainy day to come.

How do you use GIS in your work and research? I’d love to hear about it in the comments.

I defeated the ASBOG FG!

All three times that I went to the Geological Society of America conferences, I picked up something from the Association of State Boards of Geology (ASBOG) booth. I won a rather nice tape measure from them in 2015. All three times, the booth staff admonished me with “you should take the Fundamentals  of Geology exam before you forget everything you learned in university!”.

And then I found myself thinking in the summer of 2016 – what am I waiting for? I took all the necessary coursework and more that I need to be licensed, I’m working under two licensed professional geologists, why not take the exam and get on the path to making all that work official?

I ordered the RegReview study guide, said farewell to my three-times-a-week climbing gym habit so I would actually make time to study, and got to work.

I really should have taken it right out of college, but wasn’t as rusty as I had feared. Even though I felt like throwing my study guide across the room after the fourth page of ore mineral formulas, studying for the exam actually reminded me why I want to be a geoscientist. One night I was messing around with formulas for mapping groundwater draw-down and projection of cross-sections onto a map view and didn’t realize that it had gotten to be 1 AM. (I had to get up to be at a job site at 6 AM. Oops.) I got to spend quality time with fields like seismology and structural geology that don’t show up often in my day-to-day work.

Not to mention that my sister drew me this gem of a Lord of the Rings/Geology crossover: Meet the ASBOG Balrog.


So that’s how I found myself at 7 AM at the Department of Commerce building on September 30 armed with a calculator, protractor, and 1 liter thermos of steaming hot caffeine. Walking through the door, I could immediately identify my fellow geologists waiting for the exam – plaid shirts, practical shoes, Patagonia vests, and looks of acute anxiety were all giveaways among steady stream of state employees heading to the elevator.

We all walked out of the exam room four hours later, exhausted and convinced that we had failed. Thankfully, today I found out that I actually passed! With acceptable marks in all categories, even the ones I was freaked out about! (I’m talking about you, engineering geology)

When I was studying for the exam, I scoured google and reddit for advice from people who had taken the exam, and couldn’t find much. Much of the advice pertained to the second exam, (the PG), like this excellent blog post over at Accidental Remediation. In the hopes of helping someone like me taking the FG, here are some of the things I found most helpful:

  1. There is no way on earth that you can cram for this exam. I did one chapter per week in the RegReview book, and that was almost pushing it. I should have started studying earlier – the ASBOG website isn’t joking when is says six months in advance.
  2. Take a close look at the application to take the exam. I got taken by surprise by the fact that after I had submitted my exam to my states professional licensing board, and I had to submitted a completely different application and fee to the national ASBOG organization.
    1. step one: State of Tennessee Geologist Licensing Forms (or your state’s equivalent). For Tennessee, this meant filling out two forms: the Geologist FG Exam Application, and the Geologist Course Reporting Form.
    2. step two: after the application is accepting by the state board, that agency will send you a candidate request form that you will need to send, with a check attached, to ASBOG.
  3. The actual exam questions were slightly easier than the ones in the RegReview book, and didn’t need quite as much math. However, they were still by no means easy. Looking back at my university quiz and test questions, the ASBOG questions were comparable to the more difficult 25% of them. They were very similar in difficulty to the questions in the official ASBOG candidate handbook.
  4. Memorize the picky mineral characteristics/formulas and mining terms. They were on the exam, believe it or not.
  5. Don’t underestimate the power of handwritten notes…
  6. …or flashcards, either. If you use the RegReview cards, add in a few additional handmade ones for ore deposit types, water quality standards, dating methods, Bowen’s reaction series, and engineering characteristics of earth materials (elastic properties, etc).
  7. And then working the practice problems a second time.
  8. I don’t recommend bothering to study in the two days immediately before the test. I know I was too keyed-up for any more information to stick, anyways.  Eat well, try to get some sleep, and do thing that clear your head. In my case it was lunch with an old friend and wearing myself out on the rock wall.

Have you taken the exam? What impacts have being licensed (or not) had on your career? I’d love to hear your opinions in the comments.