Geology of the National Parks in Pictures - Gateway Arch National Park

My next post about the Geology of the National Parks Through Pictures is a park we visited in 2005 as I moved from Texas to New York.  

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website Dinojim.com.

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Gateway Arch National Park

While driving up from Texas to New York we were able to visit the famous Gateway Arch that was in the former Jefferson National Expansion Memorial. Although there isn't much geology associated with the steel structured arch itself, there is always geology to talk about.

The Gateway Arch is clearly the centerpiece of the park, hence the name change. The Arch itself is 630 feet tall, 630 feet wide, and goes 60 feet into the ground. It is composed of steel and concrete. The outside skin is 1/4-inch stainless steel, followed by a layer of concrete, then 3/8-inch structural steel on the inside. The shape of the Arch is termed a catenary arch, which is the shape of a free-hanging chain when held at both ends.  

As noted, the Arch descends 60 feet into the ground and is actually anchored within the St. Louis Limestone. The St. Louis Limestone is Mississippian in age (~335 million years old) and was formerly outcropped along the river's edge but extensive quarrying for use within the city has limited the availability. The St. Louis Limestone is a grey marine limestone that weathers to chalky white, sparsely fossiliferous, fine-grained, and occasionally dolomitic. Available fossils include bryozoan and echinoderm fragments. The entire city is underlain by the St. Louis Limestone, which can get up to 120 feet thick in places.

The Arch sits within the floodplain of the Mississippi River, where the floodplain is 6 to 10 miles wide. After the river front bluff of St. Louis Limestone was quarried away, construction began on levee in 1835. This enabled the waterfront to be used as a port where the goods on the larger ships from the lower Mississippi could be transferred to smaller ships for transport up the smaller upper Mississippi, Illinois, and Missouri Rivers. The original levee, made of mud, eventually was replaced with a levee made from the locally quarried St. Louis Limestone. 

They have trams that can take you to the top of the Arch where you can hang out as long as you want, however the lack of bathrooms deems that eventually you will need to leave.

Here is the view looking east, towards the Mississippi River. The sun was also at the perfect angle to capture the shadow of the Arch as well.  

Looking west you can see the other two main buildings of the Gateway Arch National Park. Here is the  Old Cathedral. From up close there are actually several building stones that are used in abundance in the building from the surrounding region. Started in 1831, the Cathedral took 3 years to complete, with new stones being added during later renovations. The sides and rear walls of the Cathedral are composed of the same St. Louis Limestone that the Arch is anchored in. These blocks were likely quarried from the nearby riverfront. The front wall and columns are of an unknown dolomite, however it is likely the Joliet limestone, a Silurian age (~430 million year old) massive, very fine-grained, tan colored stone. Windowsills throughout the cathedral are made from Mississippian age Salem Limestone (~335 million years old). These were stone products sold as "Indiana Stone" and were likely installed during renovations in the early 1960's. The steps leading up to the cathedral are crystalline pink Precambrian granite from the nearby St. Francois Mountains. These steps replaced the original sandstone steps back in the 1880's. 

Looking west down on the old Courthouse from the top of the Arch. The Courthouse also contains several different types of local building stones. Construction of the Courthouse began in 1839, however after many hiccups and delays during construction, it was not completed until 1862. Like the Cathedral, St. Louis Limestone is used extensively within the building. However, since the building has several coats of paint on it to hide variations in building stones, it is difficult to determine what other building stones had been used. One of the buildings stones was noted by NPS renovators was a crystalline fossiliferous Mississippian limestone, containing numerous unconsolidated fossil shell fragments. The above noted Salem Limestone was also used during renovations here to replace damaged to deteriorating cornice and floor elements. The columns are comprised of Ordovician age Kimmswick Limestone (~465 million years old). This is a massive, white to light grey, fossiliferous limestone. The steps are Precambrian granite porphyry from Cold Springs, Minnesota, installed during renovations in the 1950's. And lastly, the flooring throughout the Courthouse is from a variety of stones including the St. Louis Limestone, the Ordovician Plattin Limestone, sometimes called the McPhereson "marble", the Mississippian Warsaw Limestone, sometimes called the Carthage "marble", and the Cambrian Taum Sauk Limestone. 

References

https://www.gatewayarch.com/experience/about/#fun-facts

https://wonderopolis.org/wonder/how-was-the-st-louis-arch-built

https://share.mo.gov/nr/mgs/MGSData/Books/Special%20Publications/The%20Geologic%20Story%20of%20the%20St.%20Louis%20Riverfront%20-%20A%20Walking%20Tour/SP-006.pdf

https://pubs.geoscienceworld.org/sepm/jsedres/article-abstract/51/1/7/113665/Dedolomitization-in-the-Taum-Sauk-Limestone-Upper?redirectedFrom=fulltext

Geology of the National Parks in Pictures - Sleeping Bear Dunes National Lakeshore

My next post about the Geology of the National Parks Through Pictures is a park we visited back in the summer of 2005. 

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website Dinojim.com.

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Sleeping Bear Dunes National Lakeshore

On the northeastern shore of Lake Michigan, lies these monstrous dunes that run right up to the edge of the lake. Like Indiana Dunes National Park to the south, this is a glacial landscape that eventually was carved up by the lake. 

Here is a view out over Lake Michigan from the top of the dunes. When the glaciers had come through this area they had carved out the river valleys, increasing the depths and widths of the valleys in this area so much that it created the Great Lakes. The glaciers acted as giant plows, scooping up whatever was in their path and carving out the ground surface over which they rode. Towards the end of the glacial ice sheets, they acted like conveyor belts. The materials that were scooped up along the way were then deposited in piles (called moraines) of glacial debris (called till) where the glaciers melted. As the glaciers retreated (melted away) they deposited moraines along the path of their retreat.  

The top plateau of Sleeping Bear Dunes is formed by a moraine from the retreating glaciers. After the initial retreat of the glaciers, two small glacial advances were made. The first, called the Port Huron, covered the area with glaciers, further reshaping the landscape, including the previously deposited moraines. The final glacial advance ~11,800 years ago, termed the Greatlakean, terminated at the Lake Michigan shore. Sandy till deposited by this glacial advance, as well as glacial outwash sediment that contained abundant amounts of sand, were the primary sources for sand within the region, especially upon the moraine plateau. 

After the retreat of the glacier, wind and wave action helped to reform the shoreline smoothing out headlands and filling in the nooks and crannies. The lake level also fluctuated significantly during high and low periods until finally settling down to its elevation of 577 feet above sea level. Sleeping Bear Dunes were deposited when the lake level was still fairly high, at 612 feet above sea level.

Along the shoreline there are several steep drop-offs that are on average 200 to 300 feet high. Erosion by wave action over the last several thousand years had helped to emphasize these dramatic cliffs that cut into the moraine situated below the sand deposits. Wind also has an effect on the still active dunes atop of the plateau, called "perched" dunes. Wind not only moves these dunes around on top of the plateau but is capable of blowing minor amounts of new of sand up the cliff faces to add to the dunes.

Not all of the shoreline is that steep though. Here you can see a dune with the stabilizing beach grass growing fairly well along it. There are dunes along the shore as well, located below the plateau at lake height. These dunes are regularly fed with new sand from the westerly winds that blow across Lake Michigan. 

And finally we have a lovely sunset, looking out over the dune cliff face as the sun sets into Lake Michigan.

References

https://leelanau.com/dunes/dunes/sleeping-bear-dunes-geology/

https://www.earthmagazine.org/article/travels-geology-sculptures-wind-and-ice-sleeping-bear-dunes-and-pictured-rocks-national

https://pubs.usgs.gov/wri/1983/4253/report.pdf

https://pubs.geoscienceworld.org/gsa/gsabulletin/article/93/4/297/202755/Late-Woodfordian-and-Greatlakean-history-of-the

Geology of the National Parks in Pictures - Assateague Island National Seashore

 My next post about the Geology of the National Parks Through Pictures is a park we visited back in the summer of 2002. 

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website Dinojim.com.

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Assateague Island National Seashore

Back in 2002, my then girlfriend and I traveled to Assateague Island and hiked down the shoreline to camp along the beach. It was a beautiful place with tons of wild horses just roaming around. 

Here is a view of the foredunes on Assateague Island, just behind the beach deposits. Assateague Island is a type of island known as a barrier island. There are multiple ways that barrier islands can form and the formation of Assateague Island, as well as the nearby Delmarva Peninsula are extremely geologically interesting. 35 million years ago, while sea levels were much higher along the east coast of the United States than they are today, the area of where the Chesapeake Bay intersects the Atlantic Ocean was impacted by a 2 to 3 mile wide meteorite, forming a crater as deep as the Grand Canyon and as large as Rhode Island. This impact produced a depression that impacted drainage patterns in the area as sea levels started to fall, eventually leading to the formation of the Chesapeake Bay. 

Looking out into the Atlantic Ocean from the beach. Over the past 2 million years, the Delmarva Peninsula, which started as a spit (a sand bar projected into the water by ocean currents) had slowly been extending towards the south by the longshore drift. Longshore drift is the process by which waves hit a shoreline at an angle, pushing sediment up the shoreline at that angle. Then as the waves go back out to sea, they carry the sediment a little way out with them, only to be brought back in at that angle. Eventually this moves all the beach sediment slowly down the beach. If you have gone swimming in the ocean you have noticed this effect as you can often find yourself located significantly down the beach from where you first started. Here it moves from north to south, or left to right in the picture above. 

Looking north along the beach. Longshore drift in this picture would be coming towards us. As sea levels fluctuate up and down, eventually beaches are formed and on those beaches dunes are created along the back edge of the beaches called the foredunes. These dunes form just above high tide by the wind blowing sand particles away from the shoreline. During the last Ice Age, the sea levels were extremely low due to the build up of the glaciers locking up much of the water. As we have slowly been coming out of the Ice Age, sea levels have slowly been rising. The foredunes that had formed during low sea levels have eventually been flooded out by rising water levels. These now drowned dunes, act as a nucleus for sand build up as waves traveling in from the oceans hit these submerged dunes and slow down, dropping much of the sediment they carried. Eventually the submerged dunes build up enough to break the surface and become beach deposits. These island beaches, called barrier islands, not only protect the shoreline from wave energy, breaking up the waves as they come in from the ocean, but also create protect waterways behind the islands like estuaries, lagoons, and marshes. 

Another view of the foredunes, with enough vegetation on them to lock them in place from wind activity. But over time these newly formed barrier islands, continue to grow, shrink, and evolve depending on the wave activity, storm activity, and fluctuations in sea level. With sea levels constantly on the rise lately, Assateague Island is slowly being pushed landwards. This movement is both towards the south, by the longshore drift, and towards the west, by rising sea levels, resulting in the entire barrier island slowly converging with Chincoteague Island. 

References

https://www.usgs.gov/science-support/osqi/yes/national-parks/geology-assateague-island

https://www.floridaocean.org/sites/default/files/documents/PDFS/barrier-islands.pdf

Geology of the National Parks in Pictures - Antietam National Battlefield

My next post about the Geology of the National Parks Through Pictures is a park we visited back in 2002 on a Spring Break trip. 

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website Dinojim.com.

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Antietam National Battlefield

Back in 2002, my girlfriend (at the time) and I were working our way through various parks along the east coast. We hit up a small park within Maryland and had some fun there. I don't have much in the way of geological related photos but lets see what we can ring out.

To simulate Civil War war medicine, here I am having my leg amputated ("bite down on this"). This is because Civil War battlefields are notorious for quick and dirty surgeries, but can that be tied to the geology of the region? Battlefields, are often difficult to ascertain the geology of because, typically they are open, flat lying areas where the rocks are located below layers of soil. But that, in and of itself, is because of the geology. 

Antietam is identified as the bloodiest battle in American history with over 12,000 American casualties over 3 hours of fighting. This is because the landscape of the area is made up of primary two types of bedrock, limestone and dolomite. These are represented by the Chambersburg Limestone (Ordovician age), New Market Limestone (Ordovician age), Pinesburg Station Dolomite (early Ordovician age), Rockdale Run Formation (early Ordovician age), Stonehenge Limestone (Ordovician age), and Tomstown Formation (Early Cambrian age). 

Due to the erodibility of the limestone versus the dolomite, the limestone areas are often much flatter than the dolomite areas. This has a tendency to divert the fighting towards the limestone terrain. It has actually been shown that Civil War battles have a tendency to occur on limestone bedrock because of the flatter, open areas that they represent. And although limestone is known for its ability to dissolve in contact with water over time, without a caprock to prevent continuous dissolution, the area has a tendency to erode more evenly. 

References

https://www.smithsonianmag.com/history/civil-war-geology-123489220/

https://irma.nps.gov/DataStore/DownloadFile/426451

Geology of the National Parks in Pictures - Mammoth Caves National Park

My next post about the Geology of the National Parks Through Pictures is a park we visited back in 2002 on a Spring Break trip. Sorry for the terrible quality of the pictures from the cheap-even-then camera. 

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website Dinojim.com.

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Mammoth Caves National Park

Long before I ever intended on doing geological snippets on the National Parks, we visited Mammoth Cave National Park. As the longest cave system in the world, this in and of itself, is a geological wonderland. We had managed to go to the caves twice, but I only seem to have pictures from our first trip. 

The Mammoth Cave system is located within central Kentucky, along with a lot of other cave systems. However Mammoth Cave boasts the largest interconnected cave network in the world, totaling more than 405 miles of caves. Most caves form within a type of rock known as a limestone. Limestones are rocks formed by the deposition of animal life within a marine environment. Many marine animals form shells made out of mineral called calcite or similar minerals, all of which are carbonate minerals (Calcite = CaCO3). These animal life deposits could take the form of shells (such as clam shells), or even just what is called "lime mud", created by algae or the break down of shells. 

The main thing about carbonate minerals is that they dissolve in acid. When acid is added to calcite or other carbonate mineral, the acid combines with the CO3 part of the mineral to produce carbon dioxide (CO2), water (H2O), and some ions. The acid doesn't even need to be that strong. As rain water travels through the soil it picks up carbon dioxide, producing a weak acid known as carbonic acid. This type of acid, now in the groundwater, is strong enough to slowly dissolve away limestones located below the surface over the millions of years that the rocks are exposed to the groundwater. As the limestones are dissolved away, any surface features slowly collapse due to the now empty voids below. This type of landscape is called karts topography. You can see an overview of the Mammoth Caves karst here but there are many other areas where is can be better seen.  

Not all of the landscape collapses down. Frequently in cave systems, the overall strength of the limestone is strong enough to maintain the structures for a long while, until too much of the rocks are dissolved away. There is also usually a caprock, which is an indissolvable rock (often sandstone) that protects the limestone below from getting too much of the rainwater. Here is a field fairly close to the natural cave entrance of Mammoth Caves where the ground surface is fairly stable due to the caprock. However there is still active dissolution of the limestone within Mammoth Cave by not only the groundwater but active river systems in the cave. Currently flowing thorough the cave system are the Green and Nolin Rivers, totaling 23 miles in the lower caves. 

Seen here is the historic natural entrance to Mammoth Caves. Overall, the cave travels through four different rock units. Going oldest on the bottom to the youngest at the top, the rock units are the St. Louis Limestone, the Ste. Genevieve Formation, the Girkin Formation, and the Big Clifty Formation, all of which are Mississippian in age (~330 million years old). All of these formations formed on the shores of or within an ancient ocean that used to be located across the middle of North America. Most of the caves that visitors are likely to visit are within the Ste. Genevieve and Girkin Formations. 

Mammoth Caves cross section. Image courtesy of the Kentucky Geological Survey. 

The Big Clifty Formation (AKA the Big Clifty Sanstone) is composed mostly of sandstone and shale, forming the indissolvable caprock to the Mammoth Cave system. You can see the Big Clifty just below the soil as you enter the Historic Entrance pictured above. Although the Big Clifty Formation can reach 50 to 60 feet thick, generally you can only see the lower part of the formation. Below the Big Clifty at the Historic Entrance is the Girkin Limestone. The Girkin Limestone is 135 to 140 feet thick and is composed mostly of fine to coarse grained crystalline limestone, formed from the inorganic precipitation of calcite directly from the water. 

Water first entered the cave system about 10 million years ago, entering in through the upper Girkin Formation. By 3.2 million years ago, the upper cave systems were completely formed. Below the Girkin Formation, Ste. Genevieve Formation is 110 to 120 feet thick and composed of interbedded limestone and dolostone with fossils of corals, bryozoans, brachiopods, shark teeth, gastropods, and crinoids. 

Below the Ste. Genevieve Formation, the St. Louis Limestone is 175 to 200 feet thick and is composed of a mix of limestone, dolostone, sandstone, siltstone, and shale, as well as an abundance of chert nodules. The St. Louis Limestone also has a similar fossil assemblage as the Ste. Genevieve Formation. 

Within the cave systems, the cave formations are formed not only from the dissolution of limestone by carbonic acid, but also the precipitation of limestone. As the groundwater travels through cracks in the limestone and enters cave systems in the lower levels, any calcite that is dissolved within the water is left behind as water drips down. These deposits form the classic stalactites (on the ceiling), stalagmites (on the floor), and columns. They also produce other interesting formations known as flowstones as the water flows down various surfaces of the cave. Here water is both dissolving limestone as well as precipitating limestone. The specific variety of limestone that is produced by this precipitation is known as travertine. 

Here you can see a flow stone formation that forms a "curtain" where it flows down the wall to an overhang where stalactites are precipitating off of. 

References

https://www.usgs.gov/science-support/osqi/yes/national-parks/mammoth-cave-national-park

https://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/lime-mud

https://people.uwec.edu/jolhm/Cave2005/Group3/cave%20formation.htm

https://kgs.uky.edu/kgsweb/olops/pub/kgs/XSP7reduce.pdf

https://pubs.usgs.gov/sir/2008/5023/44toomey.htm