Geology of the National Parks Through Pictures - Chickamauga & Chattanooga NMP - Part 2

 My next series of posts about the Geology of the National Parks Through Pictures is for a set a parks we visited in 2018 while visiting Chattanooga for my wife's Ironman race. We hit up two parks that spread across three states. The first park in Alabama, Russell Cave NM I did earlier. Now I'm getting back to the other park.

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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Chickamauga & Chattanooga National Military Park

Chickamauga & Chattanooga NMP is a weird park because it is comprised of two distinct districts, with two very distinct geological settings, in two different states. So, that being said, I have decided to do this park in two parts, one for each state. The first part of the park in Tennessee can be found HERE. The second part of the park is located in Georgia, just a few miles south of the TN-GA border near the town of Chickamauga.

The entrance sign for the Georgia part of the park. Much more laid out and rolling fields than the steep mountainous Point Park. The park preserves the battle field from the Battle of Chickamauga during the the Civil War in the summer of 1863. 

Although battle fields typically don't have much in the way of geology, they are really just fields in most instances, the monuments that get erected there are often built from the building stones from the monument's home states. Unfortunately, more often than not, the building stones are just listed as "granite" or "marble" with no indication of where they came from. That is the case here where we have several monuments, including the 10th Wisconsin Infantry right up front here, identified as being built of granite but no idea where it came from.

Overview of Glenn Field with Wilder Brigade Monument in the distance on the left. The fields in which the battle took place are the counterparts to the Lookout Mountains to the west. This is the "valley" portion of the Ridge and Valley Province of the Appalachian Mountains, which is a series of linear NE-SW trending synclines (rocks bent like a "U") and anticlines (rocks bent like an "A"). These rocks were folded during the mountain building event (orogeny) called the Alleghenian Orogeny. This is when North America slammed into Africa around 300 million years ago (Late Pennsylvanian to Early Permian) making North America crumple up, forming part of the Appalachian Mountains. The rocks in the region are mostly made up of limestones and shales, however there are significant amounts of sandstone in the area as well. This particular valley, known as Chickamauga Valley, contain Cambrian to Ordovician age limestones and dolostones along the valley floors. 

Close up of the Wilder Brigade Monument. This particular monument had been roughly hewn out of Chickamauga Limestone. The Chickamauga Limestone, sometimes called the Chickamauga Group or Supergroup is Middle to Late Ordovician in age (~470 to 445 million years old), and can be broken up into several individual formations. This particular limestone can be found locally in northwestern Georgia, as well as northern Alabama, eastern Tennessee, and southwestern Virginia. 

The Chickamauga Limestone is light- to dark-grey, cryptocrystalline to coarsely crystalline limestone, which was deposited in deep marine water. And although it is mostly crystalline, there are some fossils including graptolites, brachipods, and conodonts. Most notably were a variety of crescent shaped structures which are likely the edges of brachiopods (as seen in the picture above). 

View of Glenn Field from the top of Wilder Brigade Monument.

Some nice canon placement shots across the valley floor.

View of the Snodgrass house, where people once lived during the battle that took place here.

References

https://georgiainfo.galileo.usg.edu/topics/geography/article/physiographic-districts/chickamauga-valley-district

https://ngmdb.usgs.gov/Geolex/UnitRefs/ChickamaugaRefs_1036.html

https://npgallery.nps.gov/GetAsset/c999de83-4d59-4d60-bffe-1d11aff956e7/

https://www.nps.gov/parkhistory/online_books/chch/hrs/chapter2.pdf

http://npshistory.com/publications/chch/adhi.pdf

Geology of the National Parks Through Pictures - Chickamauga & Chattanooga NMP - Part 1

My next series of posts about the Geology of the National Parks Through Pictures is for a set a parks we visited in 2018 while visiting Chattanooga for my wife's Ironman race. We hit up two parks that spread across three states. The first park in Alabama, Russell Cave NM I did earlier. Now I'm getting back to the other park.

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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Chickamauga & Chattanooga National Military Park

Chickamauga & Chattanooga NMP is a weird park because it is comprised of two distinct districts, with two very distinct geological settings, in two different states. So, that being said, I have decided to do this park in two parts, one for each state. The first part of the park that we visited was the part in Tennessee called Point Park. The second part in Georgia can be found HERE. This is a really cool park to get to because it is located at the top of Lookout Mountain, which is a rather steep drive up, or you can do what we did, and take the Incline Railroad up the mountain and walk over to the park from the top of the railroad. 

Here is a shot of the Incline Railroad from the top station looking down Lookout Mountain towards Chattanooga. We'll get into the geology of Lookout Mountain in a bit.

For the entrance sign at this part of the park, I took a shot of the Point Park Gate, which in and of itself, has beautiful building stones. 

Here is a closeup of the Point Park Gate to check out the sandstone blocks. The blocks are beautiful but I can't find any sources for the blocks. My assumption would be that they are a local building stone. The one that seems to fit best is the Sewanee Sandstone. This is a local building stone that has been used in the town of Swanee nearby and is also found as the caprock of Lookout Mountain. The Sewanee Sandstone is Lower Pennsylvanian in age (~320 million years old) and was deposited as barrier bar deposits. It is a course-grained, conglomeratic, cross-bedded sandstone. The cross beds are what are highlighted by the darker brown lines through the blocks.

Here is a view off towards Chattanooga towards the east. The river in the picture is the Tennessee River. Lookout Mountain is a part of the Ridge and Valley Province of the Appalachian Mountains. This is a section of linear NE-SW trending synclines (rocks bent like a "U") and anticlines (rocks bent like an "A"). These rocks were folded during the mountain building event (orogeny) called the Alleghenian Orogeny. This is when North America slammed into Africa around 300 million years ago (Late Pennsylvanian to Early Permian) making North America crumple up, forming part of the Appalachian Mountains. The rocks in the region are mostly made up of limestones and shales, however there are significant amounts of sandstone in the area, such as the ones used for the Point Park Gate above.

This is the New York Peace Monument, which was built in 1910. The building stones used for the structure are Tennessee marble and Massachusetts pink granite. Tennessee Pink Marble is interesting in that it actually isn't a marble, it is a limestone, meaning it was never metamorphosed. The "marble" even includes such sedimentary structures as cross bedding, bryozoan fossils, crinoid fossils, and stylolites. The rock is part of the Holston Formation, which formed 460 million years ago during the Middle Ordovician, along the continental shelf of Laurentia (the northern continent). The Tennessee Pink Marble is found along the eastern part of Tennessee, near Knoxville and was also used in the Jefferson Memorial and the Lincoln Memorial in DC.

A close up shot of one of the columns, highlighting the Massachusetts pink granite, although the lighting of the photo doesn't really emphasize the pinkness. The Milford Pink Granite from Massachusetts is likely the granite which was used. The granite is a 630 million year old, Proterozoic igneous rock located in and around Milford, MA, covering an area of ~100 km2. The granite was initially discovered in the 1870's and was noted for its pink quality, although there is variation within the body. The colors range from light-gray to pale orange-pink. Milford Pink Granite has also been used in the Lincoln Memorial in DC.

Although the mountain is mainly comprised of limestone and shale, there is a caprock of sandstone which covers the mountain. This is the same Sewanee Sandstone that I am guessing was used as the building stone of the Point Park Gate above.

A shaded view of the Ochs Memorial Observatory on the northern end of Point Park. The building here is noted as using a local sandstone as the building stone so I am under the assumption that it is also built using the Sewanee Sandstone. There is also a rather interesting Cherokee take on the geology of the region that was on a sign at the park: 

"At first the earth was flat and very soft and wet. The animals were anxious to get down (from above in Galunlati, beyond the arch) and sent out different birds to see if it was yet dry, but they found no place to alight and came back again to Galunlati. At last, it seemed to be time, and they sent out the Great Buzzard, the father of all the buzzards we see now. He flew all over the earth, low down near the ground, and it was still soft. When he reached the Cherokee country, he was very tired, and his wings began to flap and strike the ground, and wherever they struck the earth there was a valley, and where they turned up again there was a mountain. When the animals above saw this, they were afraid that the whole world would be mountains, so they called him back, but the Cherokee country remains full of mountains to this day." From the Native History Association

References

https://www.stoneworld.com/articles/82290-tapping-the-stone-foundation-of-sewanee

https://doi.org/10.1130/0-8137-5406-2.153

https://www.ncptt.nps.gov/buildingstone/stone/milford-pink-granite

https://mrdata.usgs.gov/geology/state/sgmc-unit.php?unit=MAZmgr%3B0

http://academic.brooklyn.cuny.edu/geology/powell/613webpage/NYCbuilding/TennesseeMarble/TennesseeMarble.htm

https://www.gettysburgdaily.com/lincoln-memorial/

https://pubs.geoscienceworld.org/sepm/jsedres/article-abstract/34/1/46/95717/The-petrology-of-lower-Pennsylvanian-Sewanee?redirectedFrom=PDF

http://www.nativehistoryassociation.org/creation.php 

https://www.nps.gov/parkhistory/online_books/chch/hrs/chapter2.pdf

Geology of the National Parks Through Pictures - Colorado National Monument

My next post about the Geology of the National Parks Through Pictures is a park we decided to go to during the quarantine when we wanted to get out but were limited on our social distancing options for Father's Day weekend. Turns out Colorado National Monument was the perfect location.

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.

Colorado State Geological symbols can also be found HERE.

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Colorado National Monument

Colorado National Monument is a park we had driven near a few times but never actually gone to before now, not realizing how truly beautiful it was. The overlooks are simply astounding and everything about the park screams geology. It is directly outside Grand Junction and Fruita, Colorado and is a quick jump from either of those cities in SW Colorado.

The western entrance to Colorado National Monument. 

Colorado National Monument is an interesting park. Most of the park is located on top of a high cliff that looks out over the Grand Valley where Fruita and Grand Junction are located. The reason for the high cliff is that the park resides on the upturned side of a giant fold. Within geology as a whole, there are several different types of folds within rock units. The most common folds are the syncline, when the rocks are bent like a "U", and the anticline, where the rocks are bent the other way like an "A". The Colorado National Monument fold is a different type of fold though, known as a monocline, where only one edge of the fold is bent. It's like an anticline with only half of the "A" is bent. You can see the cross section of rocks within the fold and the park. The oldest rocks of the fold are those located near the valley floors, which are the Upper Triassic age Chinle Formation (~200 million years old). The rock units progressively get younger until you get to the top layer of the fold, represented by the Cretaceous age Dakota Sandstone (~100 million years old). You can see the rocks in this park cover a large span of time. Image from the Rock Layers of the Monument brochure from the NPS.

View of Independence Rock from Otto's Trail. Within these large formations here we have a series of rocks. The base of the valleys are the really old rocks. Below the Chinle Formation described above is some Precambrian metamorphic rocks called the Black Canyon Group. These include gneiss, dark schists, and light pegmatites, which are all extremely hard, erosion resistant rocks. The Black Canyon Group is estimated to be 1.7 billion years old. The erosion resistance of these rocks are what caused the erosion of the valleys to essentially stall once it reached this level, unable to erode very quickly through the metamorphic layer.

Here is a view at the end of Otto's trail looking north towards Fruita in the distance. Immediately on top of the Black Canyon Group is the Chinle Formation. Between them is a gap in time equal to 1.5 billion years. This gap in time is known as an unconformity, specifically a nonconformity, where the rocks that used to be here were eroded away before the newer rocks were deposited later. These newer rocks are the 200 million year old Chinle Formation. The Chinle Formation is comprised of red mudstones, shales, conglomerates, and thin limestones. Shales and mudstones are all extremely easy to erode, so they typically form smooth slopes when eroded. That is what you see at the base of the cliffs, where the tree line starts. The Chinle Formation extends from the tree line down to about where the underlying red soil stops. The Chinle Formation was deposited in a stream and floodplain environment.

Here is a view from a little further down the main road at Grand View. I love these types of stops because they provide a display with the geology overlaid on the rocks as you see them. A picture of the geology sign is directly below to compare. Directly above the Chinle Formation is where the cliffs start. This is the Wingate Sandstone. The Wingate is a very thick bed of dune sandstone from a prehistoric desert deposited during the Lower Jurassic. Most of the geologic formations within this park are located within the Wingate.

The Wingate continues up until a slight color change in the rocks can be seen near the top of the cliff. The rocks on the very top here are more grey in color than the yellow of the Wingate. This is the Kayenta Formation, another sandstone but with more shale and conglomerate mixed in. The Kayenta Formation represents a period of time when the environment started to bounce back from the Wingate desert and rains started to fall a bit more. 

Here is a view from the Grand View looking back towards the cliff edge. You can see here the next series of rock units above the Kayenta Formation. This is the Entrada Sandstone, seen here most clearly on the right hand portion of the photograph as the smooth yellow sandstone cliff face just below a thin strip of green plants at the top of the rock series. The Entrada Sandstone is a Middle Jurassic aged sandstone (~150 million years old) that was deposited from the dunes of a nearby sea. This is the same rock formation that the arches are from at Arches National Park. 

View from the Grand View looking towards the north at Fruita.

Here is a closer look at the Entrada Sandstone where we can just barely make out the next series of rocks. Immediately on top of the Entrada Sandstone is the Wanakah Formation, a thin Middle Jurassic series of mudstones, shales, and sandstones from the lake and stream environments.

View of the canyon from Artist's Point looking down on the Wingate erosional features. 

View of the canyon wall from Upper Ute Canyon overlook. Here we get a great shot of the Wingate Sandstone (large orangy yellow sandstone on the bottom) with the Entrada Sandstone (thinner orangy yellow sandstone on top (after a break of green plants and grey rocks, which are the Kayenta Formation). On top of the Entrada is the Wanakah, and on top of the Wanakah is the highest rock formation we can see within this portion of the park, the Morrison Formation. The Morrison Formation is an Upper Jurassic age (~155 million year old) series of mudstones and occasional sandstone lenses that is world famous for its dinosaur fossils. The Morrison Formation  ranged through several terrestrial environments including lake, river, and floodplain deposits. 

Here is another geological overlay view with the geology sign below. This area shows the Black Canyon Group, small bits of the Chinle Formation, the thick Wingate Sandstone, and topped with the Kayenta Formation. We have moved far enough to the southeast of the monument now that we are looking out onto Grand Junction instead of Fruita. 

Geological overlay of the above image.

Here we get a closer look at some of the cross bedding within the Wingate Sandstone, the curved lines going through the rock unit. Cross-beds indicate that these rocks formed from sand that were once sand dunes that were eventually cemented together. 

Below we will look at some of  the several fantastic erosional features throughout the park.

View of the Coke Ovens, which are geological erosional features that are reminiscent of the old coke ovens. Coke ovens are often beehive shaped structures that process coal by burning the impurities out of coal producing a product known as "coking coal" or just "coke". These features are within the Wingate Sandstone. 

View of the Coke Ovens from the top, at the end of the Coke Ovens Trail.

Within the rock units, the faulting and joints that formed as a result of the folding create areas where erosion is able to get a foothold. Once water then starts to consolidate within those cracks, valleys begin to form, further enhancing the cracks that were there. Sandstones, and other very hard rocks, have a tendency to fracture in a grid formation. This grid formation leads to erosion that follows that pattern, as seen here with river valleys forming a right angle to one another. 

A physical view of the valleys seen in the image above. Once erosion proceeded vertically low enough, it hit the resistant Precambrian Black Canyon Group, and the erosion slowed drastically. Afterwards, erosion proceeded in a more horizontal direction, widening and lengthening the already existing valleys and canyons.

Natural joints and fractures within the rock allow erosion to slowly create spectacular features such as Balance Rock, located within the Wingate Sandstone. Water and wind erosion slowly expanded a fracture that was located between the rock and the main cliff face, leaving behind this precariously balance protrusion. 

And the last of the erosional features that I'll highlight is Window Rock, an arch within the Wingate Sandstone, seen here on the left side of the photo. The trail to Window Rock leads you right up to the top of it, however since you are basically on top of the arch (the actual arch is off limits by a fence), it is difficult to get a nice photo of it. This is another instance of erosion removing material along a preexisting crack in the rock, widening it until an arch was formed.

References

https://www.nps.gov/colm/learn/nature/precambrian-black-canyon-group.htm

https://www.outtherecolorado.com/adventures/the-coke-ovens-of-redstone/article_53cc5185-a447-556e-af48-06ddcb02ebc7.html

https://irma.nps.gov/DataStore/Reference/Profile/2259850

Geology of the National Parks Through Pictures - Rocky Mountain National Park

My next post about the Geology of the National Parks Through Pictures is a park we hit up after the wife did a race outside of Denver.

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.

Colorado State Geological symbols can also be found HERE.

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Rocky Mountain National Park

Even though there are a lot of scenic views within Rocky Mountain National Park, the basis for Rocky Mountain National Park is geology. The reason the mountains are here is geology and the features seen on the mountains are geological. So even though this isn't a strictly geological park, geology in imbibed everywhere. 

The obligatory entrance sign

The mountains within Rocky Mount National Park are a result of orogenic events (mountain building) that took place over three periods within the planets history. The first orogeny (mountain building event) took place 1.7 billion years ago during the Precambrian. This event laid down the foundation of faults that will later be activated during the most recent mountain building. The next orogeny, known as the Ancestral Rockies Orogeny, was 285 million years ago during the Pennsylvanian. Afterwards, the Ancestral Rockies were entirely eroded away, but again the faults were left behind. The final mountain building event was the one which produced the mountains we see today. This occurred 70 to 40 million years ago and is known as the Laramide Orogeny.

The Earth is made up of giant plates which are all moving around. When two plates are moving towards each other they push each other up, forming mountains. This is what is currently happening in the Himalayas where the Indian Plate is moving northward into the Eurasian Plate. As the two plates collide, the edges get "wrinkled". It is this wrinkle that are the mountains.  Here is a view of the Rocky Mountains from the visitors center. 

 The Laramide Orogeny occurred due to the presence of a plate off the western coast of the United States known as the Farallon Plate. The Farallon Plate was an oceanic plate that was pushing up against the west coast of the United States and Mexico. Since the plate was made up of oceanic crust, it was denser than the North American continental crust and therefore ended up going beneath the North American Plate in a process known as subduction. As the plate went under North America, it still ended up compressing North America, forming those mountain wrinkles. The mountain building occurred along those long ago created faults that were reactivated during this renewed time of mountain building. Eventually, most of the Farallon Plate was completely subducted, leaving behind only a small piece known as the Juan de Fuca plate off the coast of Washington and Oregon.

 Within the park there are also significant amount of glacial features, this divot out of the side of the mountain being one of them. When a glacier is forming on the side of a mountain, the snow continually accumulates near the peak. Eventually the snow builds up enough that it compresses down into ice, and then eventually the entire ice block starts to flow downhill. As the ice flows downhill it picks up rocks and starts to erode into the mountain that it is sitting on, creating a bowl shaped depression. That bowl shaped depression is what eventually becomes known as a cirque, once the glacier melts entirely away. 

 Here's the view of another cirque from a distance.

 Here are a whole bunch of glacier features, as well as some glaciers still present (where some of the snow and ice doesn't melt completely in the summer time). Within this photo we also have some more cirques. Since cirques erode down into the mountains, creating a bowl shaped depression, these often eroded down into bedrock. The bedrock creates a nice seal against water escaping and eventually can create a lake. This specific type of lake is known as a "tarn". When two cirques are on the the same mountain but going in different directions (i.e. back to back), they can form a ridge between themselves. This steep, knife-like ridge of rock is a glacial feature known as an "arête", which you can also see within the central portion of the photo.

 Here is a view looking down into a cirque. Although there is snow here, it is not a glacier until the snow starts to build up over time and compact into ice. Right now these are just seasonal snow fields.

After the glaciers move downward from the mountains, they start to fill up the valleys between the mountains. This ends up eroding the valleys in a specific pattern. When rivers erode out valleys, the valley cross section forms a "V" shape, where the stream erodes straight downward at the bottom of the V. However, when a glacier enters a valley, it is much larger and erodes over a much larger area. The result is a valley with more of a "U" shape, created as the glacier erodes on all of the edges of the valley. Here is a look towards the mountains centered on a glacial U-shaped valley.   

Another erosional glacial feature is when the glaciers make it further down slope and erode out and widen existing valleys. The valleys were initially eroded by streams and rivers, but glacial erosion widened and flattened these stream valleys far beyond what was initially dug out. After these valleys are eroded out by glaciers, eventually the glacier melts and water returns to the former streams. The large flat areas are then filled in as a series of interconnected lakes called paternoster lakes.

One of my favorite features of western National Parks is the Continental Divide. This is essentially a high point of the country where water at the divide goes one of two ways. Within this picture (which I am facing south when I took), water on the left, or eastern side all flows to the Atlantic Ocean, while all of the water on the right, or western side, all flow to the Pacific Ocean. The signs are not often perfect, but they are pretty close. The Continental Divide is actually a line of mountain ridge tops that runs up the entire length of the continent, dividing the drainage between the two oceans. There are other divides within the country as well, such as the one that divides water going north into Canada's Hudson Bay, or water going into the Great Salt Lake, which is an end-basin where water goes to die.

References

https://www.sciencedirect.com/topics/earth-and-planetary-sciences/laramide-orogeny

https://www.nps.gov/romo/learn/education/upload/Teacher_Guide_to_RMNP_Geology.pdf