If you haven’t read Part 1 of my Greenland field work experience, check it out here! If you have read it, you’re probably wondering what research we actually worked on for those three chilly weeks. What were our research goals? What type of data did we collect? And how did we collect that data? To answer those questions, I give you Part 2: An Attempt at Science.
The University of Wyoming and University of Montana’s glaciology group has become highly involved in Greenland Ice Sheet (GrIS) research over the past decade. Because the ice sheet has become of critical importance in our warming climate, many scientists are trying to better understand the dynamics of the GrIS. Our collaborative group asks questions such as, how does meltwater move through the ice sheet? What mechanisms are involved in ice sheet movement? Or, what conditions lay beneath the ice? Answers to these questions help us to better understand GrIS dynamics in a changing climate.
For this field season, we were mostly concerned with the first of those questions. More specifically, we ask: what is the fate of meltwater in the percolation zone? To better understand what the percolation zone is, let’s take a look at the different regions or zones of a glacier (Figure 1). Any glacier (or ice sheet) is divided into two main parts: the ablation zone and the accumulation zone. The ablation zone defines the lower elevations where there is net melting. In other words, over a year-long period this region has lost mass. The opposite is the accumulation zone. Here, there is net gain in mass due to snowfall. These two zones are divided by the equilibrium line altitude (ELA) where the amounts of accumulation and melting are equal. This may seem straightforward at first glance, but a rather unusual region exists within the accumulation zone. Just higher in elevation than the ELA, there is a section of the glacier where snow melts and percolates into the firn. Firn is just altered and compacted snow. We’re curious about the fate of meltwater in the percolation zone’s firn. When snow melts to water, does it flow into the firn and refreeze? Does it percolate all the way down to the glacial ice layers? Or does it runoff toward the terminus (“the snout”) of the glacier and reach the ocean?
To answer these questions, we used a variety of research techniques that look at the structure and temperature of the firn throughout the full depth of the percolation zone, which is thought to be less than 100 meters thick in this area. The five principle tools we used were coring, hot water drilling, videography, temperature sensors, and radar. Coring involves extracting long cylinders of snow, firn, and ice from the ground below us, and then logging the densities and structures of the core. To reach greater depths than with coring, we used a hot water drill to inject hot water into the ground and create a borehole (Figure 2). Once we had a completed 100-meter borehole, we extended a video camera down the hole to visual identify interesting structures (e.g. ice layers) in the firn. In both the hot water-drilled boreholes and the boreholes remaining from coring, we installed long strings of temperature sensors that measure and record the firn temperatures at increasing depths. These temperature data will be recorded for the next year or two, so we will return next summer to collect the data. The final technique we use, ground-penetrating radar, provides insight into the firn layers below our feet. By transmitting radio waves into the ground and then receiving the waves, we can observe variations in firn density and estimate water content. Together, these five techniques provide a means to better understand the behavior of meltwater in the percolation zone.
Before arriving in Greenland, I was highly intimidated by all of the research techniques we had planned to use. I had never been involved in a full field season, never cored or drilled firn, and never even stepped on a glacier for that matter. However, I found that the best way to learn something is to actually just try doing it. With the guidance of a patient and knowledgeable advisor, I learned more than I thought was possible in three short weeks. Being in the field provides such an excellent opportunity to take an immersive approach to science: living, working, and learning in the presence of what you study.
This is the final post in the series of the geology of Maine and the Bay of Fundy. To recap for those of you who might not have read my first post, I documented all the geology I saw recently on a vacation my husband and I took to Maine and New Brunswick, Canada. This is the second post all about the geology of the Bay of Fundy! This one, though, will talk about the famous rocks of the bay and how they got the unusual shapes that made them famous. Remember, the Bay of Fundy is famous because it has the highest tides on Earth.
So what do these tides do to the rocks? To answer this, let’s first go to St. Martin, to the famous Sea Caves. You might be looking at this first image and think “what caves!”? Well, this first image is taken at high tide, so the caves are almost entirely underwater. High and low tide were separated by about six hours, so we saw high tide, admired the lovely scenery, and drove to see the Fundy Trail Parkway, a park that you can drive or hike the entire way through for some GORGEOUS scenery. There are spots to pull over and get out, hike short distances, or just look out from a cliff to see some beautiful sites. Here’s a picture overlooking the Bay of Fundy – remember, these lovely coastlines were largely created by the formation, movement, and melting of glaciers.
We returned to the Sea Caves to see it at low tide-take a look! This picture is from the SAME spot, give or take a few feet. This photo should show you the height and amount of water moved by tides every day in the Bay of Fundy. The presence of these caves is due to mechanical weathering-literally, the waves associated with the tides coming in and out are quite strong and they break down the rocks. Thousands of years of these waves have created immense caves and crevasses. Once you are able to walk across the seafloor at low tide, you can truly appreciate just how incredibly large these caves are and just how strong the tides are! Here’s an image of me inside one of the caves!
There’s one last thing I want to point out about these tides-the effect that they have on living creatures! Snails and barnacles live in high abundance all over the area affected by low tide and these creatures find incredible ways to survive when the low tide means that they aren’t covered by water! Snails will gather in small cracks in rocks where water will pool; barnacles will form more in shadier areas, so the rocks will remain more damp than those exposed to the sun. Sometimes, snails will hang on to a piece of algae just to survive until the water comes back! Check out this image of a snail holding on for dear life!
Now, let’s travel north to Hopewell Park, where the most famous rocks from the Bay of Fundy are. First, let’s look at the difference between low and high tide. These images are taken just about 4 hours apart. So the rock you see here was broken off from the cliffs due to chemical weathering-water percolating through cracks and breaking them apart. But, the odd shape that you see now, where the rock is much narrower on the bottom-that’s due to mechanical weathering. Wave action over thousands of years has caused these shapes to form. These rocks CAN fall without warning (and have, even recently), so park rangers are always making sure to look for signs of instability.
To really experience high tide, my husband and I signed up to kayak through these rocks. To say that the waves here were strong is an understatement! The waves were cresting at just under 4ft-so imagine sitting down on the beach front-you’d be completely covered (if you were curious, kayaking in 4ft waves and high winds was a blast, but also a little terrifying!)! Here’s an up close picture of that same rock you saw in the previous two pictures, from the kayak! Now you can really see where the rock is narrowed at the base-the line between the narrow and wider part of the rock marks the highest the tides can go.
I hope you’ve enjoyed this series! I think one of the most important things I can say here is that this trip made me rediscover my love of geology. Sometimes, when you work long hours every day as a geologist, it can become a little hard to remember just why you love it. If you’re feeling that way, I encourage you to get out and go explore for a little while- a few hours, or even a few months, if you can!
This post is a continuation of my first post, the geology of Acadia National Park. To recap for those of you who might not have read my first post, I documented all the geology I saw recently on a vacation my husband and I took to Maine and New Brunswick, Canada. This post will be all about the geology of the Bay of Fundy! Specifically, this will be about how glaciers have shaped the geology of the area.
The Bay of Fundy is an incredibly famous geologic area for a good reason-it has the highest tides on Earth, with the highest reaching nearly 56ft! The reason why the tides are so high here has to deal with the shape of the bay-the bay narrows quite a bit (as you can see from the map), so as all the water enters the bay, it’s forced to stack up on top of each other, making the tides reach these incredible heights.
Glaciers have shaped a lot of the geology along the Bay of Fundy; as glaciers advance and retreat, they leave telltale signs. One of the best signs are when you see rocks called tillites. These rocks are made of glacial sediment. They’re fairly easy to recognize-often, you’ll see rocks with very large, poorly sorted clasts (meaning, all kinds of different sizes of sediment). These are left behind by glaciers! Here is an example of tillite along the coast of the Bay of Fundy. Look at all of the different sizes of clasts in there! This rock was found at the Irving Nature Center, St. John, New Brunswick. The wave energy in this particular area is very high, which you can tell by the lack of small sand grains and the prevalence of much larger clasts (pebbles-boulders). Another sign of glacial activity is the presence of striations on rocks. Striations are scratches in rocks that are caused by glacial ice moving over them. These glaciers can have lots of rock and sand debris within it, so as they move over rocks, it can cause a lot of surface damage to the rock. Check out this picture of striations on volcanic rocks, also from the Irving Nature Park!
Arguably, the most famous area of the Bay of Fundy is the site called Hopewell Rocks. I’ll discuss a lot more about the Hopewell Rocks in my final post, but for now, let’s talk about how glaciers shaped these famous rocks. As glaciers last retreated from these areas (meaning, the Earth warmed and glacial ice melted), the water from the glaciers filled into the ground and caused cracks to form along the coast. This is called chemical weathering. Water is a chemical and it’s the most common chemical that rocks come into contact with when we’re talking about chemical weathering. These cracks eventually caused these large rocks to be separated from the cliff line. This phenomenon might be more familiar to you when you’re driving- when roads (in colder areas, especially) have small cracks in them and water gets into those small cracks, that water can freeze, causing the crack to expand. After multiple rounds of freezing and melting, these cracks become a real problem to drivers!
During our next (and final) piece about my trip through the Bay of Fundy, we’ll look at how these famous rocks are shaped by mechanical weathering, instead of chemical!
I recently went on a trip with my husband to Maine, USA and New Brunswick, Canada to see some of the best geology these places had to offer! I’ll be showing you a lot of the gorgeous geology (and some cool biology!) through a series of posts. This first post will be all about my trip to Acadia National Park. My husband and I hiked quite a few trails (about 20 miles of trails total!) in the four days we were there and we learned quite a lot about the geology of the park from our adventures.
A lot of the rock you’ll see in the popular parts of Acadia- especially the trails in the main part of the park-will be granite. Granite is an igneous rock that formed intrusively, meaning, it formed under the surface of Earth. You can generally tell whether igneous rocks formed intrusively or extrusively (on Earth’s surface), because the sizes of the grains will be different. The magma that makes up granite cools very slowly under the surface of Earth-the slower it cools, the larger the crystals are! But, I digress. Many of the mountains in the Acadian region are made of granite. This granite was formed when two continents- Laurentia (North America) and Avalonia (eastern North America and western Great Britain) slammed together hundreds of millions of years together. When they collided, it forced a huge amount of magma to pool, creating the famous granite we see today (you can read a lot more about the creation of Acadian rocks at this site)! Here’s a photo of me climbing some of this granite on the Beehive Trail! The mountain is very steep and the trails are very narrow, so it is most safely climbed using metal ladders!
Granite is a very hard, stable rock. What that means is that it doesn’t weather away easily, like other rocks (think of how marble gravestones look like after a few decades-marble is much more easily worn down!) But after millions of years, even the toughest of rocks can start to be broken down! Take a look at these rocks here-you can see the cracks from being weathered (likely by rain!)-these cracks allow rain to penetrate into the rock and break it down even faster! To put it into perspective, think of a windshield-if you put a single crack into it, you’ve weakened the glass and further pressure can result in faster spreading of the break. Rocks respond similarly after the first cracks are formed!
I want to show you some of the cool pictures from the other side of Acadia now. This is a lesser known, but just as beautiful part of the park as the most well known part of Acadia. This area is called Schoodic Point. This is also dominated by the same gorgeous granite-but it’s got something else going on that’s really spectacular. If you take a look, you’ll see the gorgeous light colored granite…but also, intrusions of a dark colored igneous rock (called a diabase); this diabase has tiny crystals-meaning, it cooled quickly! We can tell that the dark colored rock intruded into the granite because of the Principle of Cross Cutting Relationships; this geologic principle means that if a rock “cuts across” another rock, the rock that is cutting across is younger (read more about geologic principles here).
So, with that in mind, these diabase intrusions are the remnants of later episodes of volcanic activity. There are multiple episodes of volcanic activity represented here-many of the intrusions are cut by even more intrusions! What a beautiful place. So even though this is a post about geology, I wanted to show you a little bit of the life here at Schoodic Point-the wave activity at this area is VERY high (one easy way to see that is that there’s very little sand at this coast-the wave energy is too high, so the sand gets washed away). The water crashes up onto the granite and some water will stay up there, giving a perfect spot for lots of little critters to form a home! Take a look at this small pool of water-how many critters can you see?
I experienced a more non-traditional field experience that I would like to share with everyone. I recently traveled to Japan for the 16th International Echinoderm Conference and during this conference there was a mid-week field trip to the Ise Grand Shrine. Before we left we were given a brief history on the shrine and what it symbolizes. Basically, it is meant to symbolize eternity. This shrine is rebuilt every 20 years from the ground up rather than patching issues as they arise. This ensures that the shrine ages as a whole! It is also built adjacent to the current standing shrine so every 20 years the shrine moves locations.
The shrine is built of very specific building materials and no nails are used during the construction. The rebuilding of the shrine ensures that the next generation learns the skills required to construct the temple to continue to pass along this tradition. It’s a really interesting concept and I really enjoyed getting to wander around the complex. There were also very interesting rocks as you walked up to the shrine!
The steps were mostly made of metamorphic rocks that are likely greenschist. This type of metamorphic rock is created from igneous rocks that undergo transformation under particular temperatures and pressures. The heat and pressure often comes from different land masses colliding with one another throughout time, caused by plate tectonic movements. Greenschist rocks are normally dominated by minerals that exhibit a green color such as chlorite, actinolite, and epidote. Japan has an incredibly complex tectonic history and I won’t attempt to explain it but if you are interested in learning more check out this report and the Geology of Japan by the Geological Survey of Japan.
Whenever you are traveling or even in your hometown, make sure to look out for what buildings, stairs, and more are made of! You’ll be surprised at the extraordinary details you will uncover in the rocks that surround you in your daily life.
The tent glows orange as the sun shines in, waking me up to a cold, crisp morning. Only, it’s not really morning yet. It’s 3:00 AM and far from breakfast time. The wind rattles the thin flaps of my tent, reminding me of the powerful cold outside of my warm haven. This is the Greenland Ice Sheet. This is the icy expanse where the summer sun barely sets, the temperatures are well below freezing, and the wind can numb your face. This is also where I work.
I recently returned from three weeks of field work on the Greenland Ice Sheet (GrIS) where I helped collect data for the University of Wyoming and the University of Montana’s glaciology group. Our collaborative group consists of two lead professors (one at each university) and a handful of graduate students, postdocs, and associates. This year, six of us flew to Greenland to collect data for our ongoing study of ice sheet dynamics. This was my first field season on the GrIS, and it was like no other experience I have ever had.
Where did we go?
Nestled between the Arctic and the Atlantic Oceans lies an icy mecca for glaciologists: Greenland. Greenland is an island almost entirely covered by an ice sheet, which is a body of glacier ice that covers a very large area (greater than 50,000 square kilometers). Today, ice sheets blanket both Antarctica and Greenland (Figure 1; at left). If the GrIS were to melt it could raise sea level by an astounding 7.2 meters (Church and Gregory, 2001). With such potential for catastrophe in a warming climate, the GrIS has become the center of many studies investigating glaciology, climatology, oceanography, and much more.
Our group set off for the GrIS with the goal of better understanding meltwater flow in the accumulation zone. This is a region of the ice sheet where there is net accumulation of snow. We set up our field site on a snowy spot called Crawford Point (Figure 1, in black square). Aside from a weather station on the horizon, the views were the same in every direction: a flat white ground and a clear blue sky. Of course, that was on a “good weather day.” We had our fair share of days when ground blizzards prevented us from seeing more than a few feet ahead, or when clouds rolled in and the world around us became an empty whiteness.
Figure 1 (on the left) is of the sites of interest in Greenland. Kangerlussuaq (indicated by the yellow circle) is a small municipality of about 500 people. Located next to the ice sheet, Kanger (for short) occupies a flat region at the eastern end of a deep fjord. In fact, Kangerlussuaq translates to “big fjord” in Greenlandic. During WWII, it was founded by the U.S. and used as a U.S. airbase. Though no longer an active military base, Kanger is the site of Greenland’s largest airport and is almost entirely dependent on tourism. Our field site (Crawford Point) sits within the square on the ice sheet.
How did we get there?
From the United States, the journey to the GrIS is rich with excitement and with boredom. Most of us flew into Albany, New York and then took a military flight to Greenland. The Stratton Air National Guard Base runs periodic flights from Schenectady, New York to Greenland with their C-130 planes (Figure 2). These are training flights, which means that the pilot and the on-board mechanics are practicing ensuring that these planes run perfectly. Because of that, successfully leaving the base took two days and a few attempts. At one point, we departed on the plane and flew for about an hour before turning around and landing. Finally, we arrived in Kangerlussuaq, which is a small town on the southwest coast of Greenland (Figure 1).
In Kangerlussuaq, we worked for a few days as we prepared our gear and instrumentation for a successful field season. A massive amount of planning and work goes into field preparation, because once we’re out on the ice sheet, there’s little chance of deliveries or spare parts. When our day to fly out to the site finally came, we were ready. A Twin Otter plane (Figure 2) flew us an hour and a half from Kangerlussuaq to Crawford Point. We needed four flights to bring ourselves and all of our gear to the field site, and three flights to leave.
What’s it like to live and work on an ice sheet?
Life on the ice sheet is thoroughly unusual. At Crawford Point, we set up six personal tents, a cook tent, and a work tent (Figure 3). We also dug out a latrine in the snow, which we covered with a tarp to keep out of the wind. The latrine experience was…interesting, to say the least. We actually used our core barrel, which is designed to extract cores of snow and ice, to create a toilet (Figure 4).
Each day we’d eat a modest breakfast and lunch together, and then we would take turns cooking dinner on our Coleman camp stove. The meals became somewhat repetitive, but I appreciated having a warm and filling dinner after a day’s work. However, by the ended of the trip I detested beef jerky, I couldn’t eat another bite of cheese (which is saying a lot, because I love cheese), and all I could think about was a fresh, green salad. Still, I was grateful to have sufficient food while living in a wildly unlivable place.
Aside from the hundreds to thousands of meters of ice and snow that cover Greenland, what really makes the ice sheet uninhabitable is the weather. The cold air and blistering wind demanded rather intense clothing and gear. Every day I wore gigantic triple-layer Baffin boots, wool socks, a thermal base layer, fleece-lined pants, snow pants, a pullover fleece, a heavy jacket, a neck warmer, a hat, thick gloves, and either polarized sunglasses or ski goggles. Getting ready in the morning was quite the feat. One of the many challenges was actually completing work while wearing so many clothes. I would often have to pull off a glove to tighten a small screw, or shed a few layers after I warmed up from shoveling.
Luckily, after our three weeks on the ice sheet, our remaining time in Kangerlussuaq was warm and sunny. We took a day and drove out to the ice sheet margin (yes, you can do that), where we hiked to the Russell Glacier (Figure 5). Standing at the edge of the ice sheet was a humbling and breathtaking moment. The ice glowed blue, the milky river roared as it flowed next to the glacier, and an occasional crash could be heard as the glacier calved into the flowing river. This one moment shifted my perspective of so many things. Those three weeks of field work, the months of lab work, and these couple of years of my master’s finally fit in a bigger picture that I could see right before me. And in that moment, the struggling graduate student in me found the motivation and confidence I needed to keep working, learning, and progressing.
Stay tuned for Part 2 where I discuss the scientific work we completed!
Church, J.A., Gregory, J.M., 2001. Changes in Sea Level, in: Houghton, J.T., Ding, Y., Griggs, D.J., Noguer, M., van der Linden, P.J., Dai, X., Maskell, K., Johnson, C.A. (Eds.), Climate Change 2001: The Scientific Basis, Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, pp. 639–694.
Geology is the physical manifestation of time. The rocky foundations of our planet are the consequence of billions of years of natural processes, many of which continue today. The record of this extensive history is visible not only as layers of rock, but also in what is missing. Although often unnoticeable on human timescales, steady erosion by wind, water, and ice is a tremendous force over millennia. And across millions of years, entire mountain ranges can be uplifted, ground down to their roots, and the resulting sediments compacted into rock and uplifted into mountains anew.
By definition, gorges and canyons are among the best places to view the results of erosion, often combining exposed bedrock with more superficial—but no less interesting—features carved by running water. The bedrock may also record evidence for its own intriguing origin, adding more layers to the story (pun only half intended). The American West is well known for such exposures, the Grand Canyon foremost among them, but the East and Midwest also have their share, most cutting through Paleozoic strata: Letchworth Gorge and Niagara Gorge in New York, the Kentucky River Palisades and Red River Gorge in Kentucky, and many others.
Ohio has a number of notable gorges, many easily accessible to visitors within regional or national parks. Clifton Gorge, in John Bryan State Park near Dayton, cuts through Silurian strata that are age-equivalent to those at Niagara Falls. Numerous small gorges and valleys near Cleveland slice through Upper Devonian, Lower Mississippian, and Lower Pennsylvanian rocks, including the great Cuyahoga Valley (and its eponymous National Park). And south-central Ohio is home to the Hocking Hills, where great sandstone cliffs form ridges, gorges, and natural bridges within a lush, relatively undeveloped forest.
Situated near the western edge of the Allegheny Plateau, about 45 miles (~70 kilometers) southeast of Columbus, the Hocking Hills expose shales and sandstones of Late Paleozoic age. Unlike the northern and western regions of Ohio, this area was not beveled flat by glaciers during the Pleistocene and thus retains a rugged topography. Hocking Hills State Park, as well as a variety of other nearby nature preserves and local parks, is the iconic centerpiece of this scenic area, a popular destination for hikers and other nature enthusiasts. The park contains numerous gorges, waterfalls, “caves”, and cliffs, all worn out of a picturesque orange to tan sandstone.
This rock is the Black Hand Sandstone. Early Mississippian in age (roughly 355 million years old), the Black Hand is a coarse, sometimes conglomeratic quartz sandstone. It is massive in nature, without many discrete beds or major changes in its consistency. However, a number of features are visible at some localities, including cross-bedding, the angled bedding of ancient ripples or dunes, and graded beds, where layers of coarse pebbles transition upward into layers of smaller pebbles and then into sand, an indication of sorting by water.
Another common feature of the Black Hand is liesegang banding, concentric, sometimes twisty patterns of rusty staining. In contrast to cross-bedding and graded beds, which show evidence of what was going on at the time when the sand was deposited, liesegang banding formed much later, as groundwater percolated through the sandstone, carrying iron and other minerals with it. These minerals precipitated out of solution over time, forming the colorful bands. This can be seen as a form of weathering, rather than rock formation, though the distinction is rather blurred in this case as the bands can comprise lumps and stringers that are more resistant than the surrounding sandstone.
A number of waterfalls that cascade through the local gorges, including the Upper and Lower Falls near Old Man’s Cave as well as the nearby Cedar Falls. These falls have cut smooth channels into the Black Hand.
Geologists consider the Black Hand Sandstone a member of the Cuyahoga Formation. The sandstone’s lower contact is apparently erosional, with the sandstones of the Black Hand cutting down into the shales and siltstones of the Fairfield Member of the Cuyahoga Formation below. Meanwhile, the top of the Black Hand is capped by thin conglomerate, the Byrne Member of the Logan Formation. The Logan is also sandstone-rich, but less massive than the Black Hand below and may have been deposited in deeper water.
Several hypotheses have been put forward to explain the origin of the Black Hand. One suggests that it is a part of a great delta, deposited offshore in the shallow sea that blanketed the midcontinent during the Mississippian. Another proposes that the Black Hand is in fact a channel itself, formed in an estuary or river that carved its way through the underlying strata during a brief episode of low sea level. In either case, the relatively large and well-worn quartz pebbles and sand that make up the sandstone must have come from land to the east, near what are today the Appalachian Mountains. Research on this matter is ongoing at the Ohio Geological Survey and elsewhere.
While Hocking Hills may be the most famous exposure of Black Hand Sandstone, it is by no means the only one. The name was coined for prominent exposures of the rock along Black Hand Gorge on the Licking River east of Newark, Ohio. (The Gorge itself is so-named for a Native American petroglyph featuring a large black hand that was once emblazoned on one of its sandstone walls; sadly, this rock art was destroyed by 19th century construction in the Gorge. The name may also be spelled Blackhand, but the split version is preferred herein.)
Thus Black Hand Gorge is the type locality of the Black Hand Sandstone, the primary place that geologists should refer to when determining what the Black Hand Sandstone is, what it correlates to, and other questions. Although the process of naming rock units is now codified by the rules of the International Commission on Stratigraphy, rock units were less rigorously defined in the 19th and early 20th century. Additionally, some localities that once provided excellent exposures are now gone, naturally weathered away, covered by vegetation, flooded, or destroyed by later human development.
Fortunately, the Black Hand is still well exposed in its type area, easily accessible from a hike-bike trail that follows the Licking River through the gorge, passing sandstone cliffs, fallen boulders, and old quarries. In addition to the Gorge itself, nearby roadcuts afford excellent views of the sandstone cliffs to casual observers.
True Black Hand Sandstone is only exposed in Ohio. However, some other sandstones in nearby states are believed to be of a similar, perhaps even equivalent, age, including the Burgoon Sandstone of Pennsylvania and the Marshall Sandstone of Michigan. Elsewhere, such as in northern Kentucky, the same timespan is represented by shales and is much thinner. It is sobering to note that the time period that forms towering cliffs in central Ohio is elsewhere represented by just a meter or so of mud or, in others, by nothing at all.
Similarly scenic sandstone gorges are exposed throughout the Midwest, including the previously mentioned Red River Gorge in Kentucky and Turkey Run State Park in Indiana. However, these sandstones are typically younger in age than the Black Hand, often Pennsylvanian, deposited as the American midcontinent sea was shrinking into oblivion.
At the end of January, I was in College Station, Texas sampling sediment cores from my recent IODP expedition (more to come on that soon!) and editing our science chapters. It just so happened that while I was in Texas, I also celebrated my birthday. Of course, I had to do something extra fun, so my friend and I (who also sailed with me last summer in the Tasman Sea) went fossil collecting!
College Station is a relatively small town in southeast Texas, made famous as it is the home of Texas A & M University. There’s plenty of bars and restaurants, dancing spots and cowboy hats (seriously, I’ve never seen so many people wearing cowboy boots!). But if you know where to look, College Station is also home to another gem: Eocene-aged (~41 million years ago) fossils!
It just so happened that while I was visiting College Station, I was given a 2018 silver Camaro by the rental car company. Needless to say, we were paleontologists cruising around in style! So my friend and I hopped in the car in our best fossil-collecting gear and made the 15 minute trip to find the ‘most fossiliferous site in Texas’. The outcrop itself is under the Whiskey Bridge on the Brazos River, a bit closer to Bryan, TX than College Station, really. The parking area was located near the bridge, which required pulling off the interstate on a dirt road to get to. Once we were there, it was a short hike under the bridge, and we were instantly in fossil haven!
During the Eocene, this part of Texas was covered by a shallow sea, probably between the shore and the shelf-slope margin, with the shoreline estimated to be about 50 miles away. So, this area was never very deep, but comparable to the continental margin of the east coast U.S. today. Because the water was deep enough that energy from waves didn’t reach the bottom, fine-grained sediments accumulated here. Most of the outcrop was very fine-grained and dark in color, which geologists would call a mudstone. The dark color indicates that the rock is high in organic material from animals, plankton, algae, and bacterial that lived in the upper water column when the sea was here. There are also sandstones preserved at this location, indicating that sea level dropped at one point, and that major storms likely brought in thin sands from shore.
It’s partly due to the fine-grained material that tons of delicate, tiny fossils were preserved in the strata. The dominant fossils that can be found at this location are invertebrates, including gastropods (snails), bivalves, scaphopods, bryozoa, and corals. There are few vertebrate fossils preserved, such as shark teeth, gar teeth, otoliths (fish ear bones), and squid beaks. Even rare trace fossils (preserved movements and burrows from animals) can be found, including coiled worm tubes. We didn’t have much time to collect, as we were just supposed to be gone for about an hour over lunch.
Even though we didn’t have much time at the outcrop, we sure did leave with some awesome fossils! Most of what we found were gastropods- species of Pseudoliva, Latirus, Protosurcula, and Turritella. All were small, with some only being about 3 mm in length! There were few clam shells, as they were mostly delicate and fell apart when we tried to pry them out of the sediments. I felt pretty lucky to have found a fish otolith, or inner ear bone (I didn’t realize that’s what it was until I took it out to write this post)! Towards the end of our trip, my friend found a large (~2 inch) shark tooth! It was her first time finding one, so that was pretty thrilling! Content with our finds, we hopped in the car, muddy and happy, to head back to sample cores in College Station.
But unfortunately, that wasn’t the end of our journey that day. After being on the interstate for 2 minutes, I was pulled over by a state trooper for speeding 3 mph over the speed limit. The officer asked us where we were going, and that he was only going to give me a warning. I then had to get out of the car to get my license (it was in my book bag in the trunk, with my fossils) when the officer asked what was in my bags. Happy for the distraction, I enthusiastically showed him my fossils and began prattling on about the Eocene, in hopes he would lose interest and let us go. Instead, he was totally interested in the geologic facts I was spouting at him! He then said, ‘I wondered what you two were doing under the bridge’.
So as it turns out, driving a new Camaro onto a muddy dirt road near a bridge is a great way to gain the attention of state troopers. I’ll be sticking to my muddy, beat up Jeep for future fossil collecting trips 🙂
Click here for a link to field trip guides, fossil ID guides, an outcrop guide, and a link to a paper about the Whiskey Bridge outcrop!
Last summer, I was lucky enough to be chosen as one of the scientists to sail on the International Ocean Discovery Program Expedition 371 to the Tasman Sea (read more about my adventure here). The ship we sailed on, the JOIDES Resolution, left from the port of Townsville, Australia. Because I was already flying to the Southern Hemisphere, my husband and I decided it was the perfect opportunity to take our delayed honeymoon (we had been married two years at that point, but better late than never!). We stayed on Magnetic Island, located right offshore from the city of Townsville for a week, sight seeing, koala-petting (Queensland is one of the few places in the world that allows you to pet wild koalas), and snorkeling.
Being a naturalist and animal-lover, I have quite a lengthy bucket list. One of the items on that list was to snorkel the Great Barrier Reef. Lucky for me, the reef was just a 2 hour boat ride from Magnetic Island! My husband and I signed up months in advance for a snorkeling adventure on the reef, and we were both extremely excited about it! I prepared for the snorkeling adventure by doing extensive research on the reef, learning species of corals, fish, and sharks that are common on the reef, and also what human-made products (such as sunscreen) were harmful to the reef so we could avoid using them the day of our snorkel. But I also had to prepare myself mentally for what I knew was unavoidable: witnessing a reef community in peril.
Before I explain, allow me to dazzle you with reef facts. Reefs all over the world are amazing places (OK, this is probably more of an opinion, but I’m not wrong, right?). They are home to a huge number of animal species, all who interact with each other. Reefs themselves are defined by the community of corals, fish, crabs, etc. that live together. Reefs are located in warm, shallow, clear waters, and that is why they are found in tropical waters. Reefs occur all across the world, but the biggest and most impressive reef, by far, is the Great Barrier Reef. Check out this Google Street View of Heron Island, Great Barrier Reef to see some of the wildlife and coral species that live on the reef.
The Great Barrier Reef (I’ll refer to it as the GBR from here) stretches 2,300 kilometers (1,430 miles) along the Queensland (northeastern Australia) coastline. It covers about 344,400 square kilometers (132,974 square miles) of area, which is approximately the size of 70 million football fields, or the size of Italy. Because of its size, the GBR is visible from space, and is listed as one of the 7 wonders of the world. Together, the GBR is made up of 2,900 individual reefs, and contains 600 continental islands. It also includes about 300 coral cays (cays, or keys, are small sandy areas located near a coral reef) and ~150 mangrove islands (mangroves are an important plant that live along coastlines; their roots offer protection for small fish and animals and help stabilize the soil in which they grow).
The reef itself is home to over 1,625 fish species, which accounts for ~10% of the world’s fish species! The fish rely on over 600 species of corals for protection and shelter. Over 133 species of sharks and rays also inhabit the reef, feeding off fish. Sea snakes slither their way across the reef, with about 14 different species found in the GBR. 30 species of whales and dolphins also visit the warm, clear waters of the reef to raise their young every year. Of the 7 species of marine turtles alive today, 6 can be found in the GBR. Thus, the GBR is a true natural treasure, with its beautiful marine life, vibrantly colored corals, and abundance of geographic features.
Corals first appeared in the rock record ~548 million years ago during the Cambrian Period. True reefs didn’t make an appearance until about 100 million years later, during the Ordovician Period. These reefs were very different from our reefs today, but the point is, they have survived all 5 major mass extinctions in Earth’s history, and have become extremely successful. But all of that is changing today with global climate change. Reefs all over the world are in dying because of us, humans. It is estimated that from 1985-2012, about 50% of the GBR corals have died (De’ath et al., 2012).
Global climate change caused by humans expelling carbon dioxide (CO2), a greenhouse gas, at an accelerated rate is the leading cause of coral reef decline. As our atmosphere warms, our oceans are also warming. The oceans absorb about 93% of atmospheric heat. Although corals thrive in warm waters, they have a very narrow temperature tolerance (most can live in waters no less than 64 degrees Fahrenheit, and no more than 84 degrees Fahrenheit). When waters become too warm for the corals, they become extremely stressed. Prolonged stress leads to coral bleaching events. This occurs when corals expel the algae, called zooxanthellae, that live in their tissue. The zooxanthellae are what give corals their colors, so after expulsion, the coral turns white. Corals can survive without their zooxanthellae for a short period of time, but if they don’t return, the coral then dies. Check out this page and graphic by NOAA to understand more about coral bleaching.
Coral skeletons are made of calcium carbonate, or calcite (CaCO3). This mineral is also what bivalves and gastropods make their shells out of, so it is commonly found in reef environments. As humans pump more CO2 into the atmosphere, the oceans not only absorb heat, they also absorb this CO2 (about 30% of the CO2 released by humans has been absorbed by our oceans). When CO2 is dissolved in seawater, it creates biocarbonate ions, carbonate ions, free hydrogen ions, and carbonic acid (read more about this process on our ‘Ocean Chemistry & Acidification‘ page). The amount of free hydrogen ions, H+, are what causes ocean waters to become more acidic or basic. An increase in H+ ions leads to the ocean becoming acidic, whereas a decrease in H+ ions leads to more basic waters. So as the oceans absorb more CO2, they become more acidic. Calcium carbonate, what corals make their skeletons out of, dissolve in the presence of acid. So not only are the corals stressed from increased water temperatures, it is also harder for them to grow and build colonies because they are dissolving in increasingly acidic waters.
I was well aware of the effects of global climate change on reef communities before I snorkeled the GBR (at this time, one of the worse coral bleaching events was taking place), but I had never seen the effects of human life on the reefs up close and personal. When we jumped off the boat (which was aptly named ‘Adrenaline’) at Lodestone Reef, I was instantly blown away by the wildlife swimming all around me. Sea cucumbers, starfish, and fish were everywhere, as were several species of coral! Elkhorn coral, brain coral, and species of table coral were abundant all around us. I was in total and absolute awe.
But it didn’t take long to find stressed, dying, and dead corals. Healthy corals are vibrantly colored, while some are flesh-colored. Stressed corals experiencing bleaching events are white, and those that are dead appear black. Dead corals will also have wispy bacteria hanging off the skeletons, as they are feeding off the decaying flesh of the animal. My heart sank faster than an anchor thrown overboard when I first witnessed the stressed, dying, and dead corals. Here I was, in the midst of the world’s largest, most wondrous reef, and it was being decimated. Suddenly, I was overcome with guilt: Guilt at not living a more earth-friendly lifestyle, guilt at not talking about the effects of climate change and its effects on reefs more to my students and the public, guilt that humans are carelessly destroying our Earth’s most precious resources. I was, in fact, witness to one of the largest, most extensive mass murders taking place in my lifetime: the death of our coral reefs.
But I’m not one to end on a sad note; rather, I’m hopeful that we can help our reefs (and all marine life) rebound from the damages we have incurred. There are several organizations that are committed to protecting the Great Barrier Reef and reefs all around the world. Some countries have created fishing restrictions and regulations for their reefs to protect the fish and marine communities that inhabit them. The Paris Agreement, a coalition of over 195 countries, was created in 2015 to curb global CO2 emissions (as of writing this post, the U.S. is still a member of the agreement, but has plans to withdraw by November 2020). Scientists are gathering data on our reefs to quantify how fast they are responding to climate change, and are also working with aquariums to regrow species of corals for release back into the wild. As an individual, you can contribute to protecting our reefs in quite a few ways. First, you can actively vote for government officials that have a track record in supporting science and curbing CO2 emissions. Second, recycle. Most of our trash ends up in the oceans, and that leads to another set of problems for marine life. Third, you can reduce the amount of plastics you use in your daily life by refusing straws at restaurants, using reusable bags, baggies, and containers. Fourth, reduce the amount of time you spend driving a car. Instead, take public transportation, ride a bike, walk, or carpool with friends and family. All of these activities reduce your carbon footprint. Lastly, you can donate to foundations and organizations that work to protect our reefs.
Here’s a list of foundations and organizations that are committed to protecting our reefs, and places where you can find additional information about reefs:
I spend my time working on lectures, reading books, or annotating scientific papers. But, every once in a while, I get to collect fossils and do field work. I haven’t been out in the field since June of 2017. On January 13th and 14th of this year, I spent the weekend collecting fossils from Franklin County and Huntsville, Alabama. These areas around the state consists of limestones that date back during Mississippian period (Lower Carboniferous) ~355-325 million years old. These limestones formed in deep waters where at the time the geography of North Alabama was very different.
In these ancient shallows seas was a large diversity of sea life consisting of brachiopods, rugose corals, crinoids, blastoids, bryozoans, trilobites, and even a few early sharks. Now, their remains makeup the Lower Bangor Limestone Formation and the Lower/Upper Monteagle Limestone Formation of North Alabama. On January 13th the crew headed out to collect fossils from the Lower Bangor Limestone Formation. On our way the site, fossil collector Asa and I decided pull over at a local rock outcrop to save time. The outcrop is part of the Hartselle Formation which consists of fossiliferous and oolithic sandstones. Stratigraphically, the Hartselle Formation is right underneath the Bangor Limestone Formation. So, in other words, we were getting close to our main collecting site.
As we pulled up to the lakeshore, we began to pack up our tools and scout around to look for fossils. Limestones slabs were waiting for us to examine and chip away with our rock hammers. At the first site we found many fossils including a few crinoid calyces, trilobite fragments, Archimedes bryozoans, trace fossils, and one small shark tooth. Asa found a beautifully preserved echinoid and edrioasteroid. After the crew was done collecting at site one, we packed up and began to travel to site two of the Lower Bangor Limestone Formation. We pulled up to to the lakeshore once again. This time the men and women split up to look for fossils. Nathan, Asa, and Dylan scouted around to look for fossils.
It wasn’t until about 5 minutes later that I noticed that the the loose sediment on the ground contained a plethora of fossils that the lake water sifted back and forth over time. I spent a lot of my time lying on the ground picking up crinoid stems, ossicles, blastoid thecae (bodies), brachiopods, and even a few echinoid (sea urchin) fragments. After day one was over for fossil hunting, we began to day 2 of fossil collecting. On January 14th, Asa, Jess, and I went to fossil collect in the Upper/Lower portions of the Monteagle Limestone Formation. At location one we stopped by a small outcropping of limestone. We began looking up and down to look for fossils.
I found a good number of blastoids and great pieces of crinoidal limestone. After we collected material from site one, we began to travel to site two. Site two was much better for finding fossils. Asa and I began to inspect the very top of the rock outcrops. Fossiliferous sediment was then collected to sift through and use for educational purposes. I began to look for fossils from the bottom of the outcrop and collected crinoid stems and a large amounts of Pentremites, a common blastoid from the Mississippian. Just as we began to leave, Asa found a tooth from a Carboniferous aged cartilaginous fish called Chomatodus. The trip was a very successful one. We all spent the weekend and collecting fossils and enjoying each other’s company.