Sunday, October 06, 2019

Geology Through Literature - Good Omens


Geology Through Literature: Good Omens


As I wend my way through the 100 Greatest Books of all time, I often come across geological references within them. This one was a bit of a different one, because of the nature of the authors, the geological reference is more comedic in spirit and not meant to be taken literally. 



The book starts off with the history of the Universe, or the history of the Universe as it needs to be for this book (keep in mind, the authors are not serious, this is entirely a joke).
"Current theories on the creation of the Universe state that, if it was created at all and didn't just start, as it were, unofficially, it came into being between ten and twenty thousand million years ago. By the same token the earth itself is generally supposed to be about four and a half thousand million years old. 
These dates are incorrect. 
Medieval Jewish scholars put the date of Creation at 3760 B.C. Greek Orthodox theologians put Creation as far back as 5508 B.C. 
These suggestions are also incorrect. 
Archbishop James Ussher (1580-1656) published Annales Vetoris et Novi Testamenti in 1654, which suggested that the Heaven and the Earth were created in 4004 B.C. One of his aides took the calculation further, and was able to announce triumphantly that the Earth was created on Sunday the 21st of October, 4004 B.C., at exactly 9:00 A.M., because God liked to get work done early in the morning while he was feeling fresh. 
This too was incorrect. By almost a quarter of an hour. 
The whole business with the fossilized dinosaur skeletons was a joke the paleontologists haven't seen yet."
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The age of the Universe has been a work in progress for the the entirety of the Scientific Revolution and long before that. As Good Omens states, scientists do actually place the origins of the Universe between 10 and 20 billion years ago. The age of the Earth has also been a work in progress since people started to wonder about such things. There are multiple people who have been influential in determine the age of the Earth, both in good ways and in bad. The following is a list of people and their contributions to the age of the Earth.

- 1654: Lord Ussher - Lord Ussher used the Bible to determine the age of the Earth back dating the ages of the people mentioned in the book and calculated out that the Earth was born in 4004 BC. Ussher used the death of King Nebuchadnezzar as a reliable date from which to start and worked backwards from there using the Bible as his only "reliable" source of of information. He eventually worked backwards to get a final date of October 23rd (not the 21st as Good Omens proclaims), 4004 BC. The date itself was based on Ussher's assumption that since the Jewish calendar begins in Fall, and the week obviously started on a Sunday, he picked the first Sunday following the autumnal equinox in 4004 BC. The equinox itself has shifted through time on the calendar due to inaccuracies and adjustments, so that explains the October equinox and not the typical September one.

- 1788: James Hutton - James Hutton, often touted as the Father of Geology, developed the Principle of Uniformitarianism, which stated that the present is key to the past and that all processes happening on Earth today are the same ones that happened on the Earth in the past. This means that when we have ripples and mud cracks in modern day sediments, they can help us identify ripple marks and mud cracks in the rock record. Since everything happening today has happened in the past and erosion and deposition are incredibly slow processes then the age of the Earth must be very, very old. Although he couldn't be sure of an exact age of the Earth, one could easily assume the Earth was millions or even billions of years old based on the rates of modern day erosion and sedimentation.

- 1800's: Following Hutton several scientists tried to quantify the rate of sedimentation to calculate the age of the Earth from these rates. The ages produced ranged from several 100 million years to billions of year. Unfortunately though, the lack of constants, such as inconsistent rates of sedimentation, and limited knowledge of the entirety of the rock record at the time, made such estimates fraught with errors and miscalculations.

- 1862: Lord Kelvin - Taking a step back from Hutton's immensely old estimate, Lord Kelvin as an expert in thermodynamics, entered the picture. Lord Kelvin determined that the Earth must have formed from a molten state and slowly cooled through time. Knowing the size of the Earth and the rate of cooling, as well as the current estimated temperature of the Earth, he was able to determine that the age of the Earth was between 20 and 100 million years old. Lord Kelvin did have a significant blind spot in his calculations though because it wasn't discovered yet: radioactivity. The process of radioactivity releases heat as elements decay and the Earth is riddled with radioactive elements, which are able to slow the rate of cooling and also provide an internal source of heat for the Earth.

- 1897: Henri Becquerel - Not directly tied with the age of the Earth, Becquerel discovered one of the primary driving forces for future age dating research, radioactivity by the emission of x-rays from uranium salts.

- 1902: Marie Curie - Also not a person working directly on determining the age of the Earth, Marie Curie's work on radioactivity propelled Becquerel's discovery into the realm of future possibilities. Her work with radioactivity helped to explain the phenomena and enable scientists to use it for age dating. Radioactivity is the process by which unstable atoms (termed the parent elements) eventually decay down to stable atoms (termed the daughter elements). This decay, that takes place in the 1-to-1 ratio (1 parent decays to 1 daughter) enabled future scientists to count the number of parents and daughters and use the ratio to determine the age of rocks on Earth. The decay of these elements occurs over a set period of time known as a "half-life". The half life of a radioactive element is the amount of time it takes for half of the parent to decay to the daughter. These half-lives were determined to be very stable and are what makes radioactive dating possible. The discovery of radioactivity and the release of energy from these atoms invalidated the vaunted Lord Kelvin's predictions.

- 1904: Ernest Rutherford - Rutherford was one of the the first to recognize the potential of radioactivity to be used for dating, very shortly after Curie's discoveries. His calculations for determining the Earth's age dated the Earth using the decay of Radium to Helium, which produced results initially at 40 million years (Ma). His dates were then revised to 140 Ma (1905), and eventually to 500 Ma (1906).

- 1905: J.W. Strutt - Using similar methods to Rutherford, Strutt was able to produce results giving an age of 2.4 Ga (billion years). Although, by now it was recognized how poor an estimate the Radium-Helium dating methods was because Helium, being a gas, could leak out of the mineral. This would end up producing a caluclated age far less than what they likely were.

- 1907: Bertram Boltwood - Having realized the problem with the Radium-Helium decay pair, Boltwood suggested using Uranium-Lead, which would produce far less leakages. His age estimate of 2.2 Ga however was found to have problems since several elements also produce lead and would inflate the age estimate.

- 1920's: During the 1910's through the 1930's various scientists bounced around with the age of the Earth from several hundred million to a few billion years. Some by estimates based on other people's works and some on new methods of radioactive dating, but nothing concrete was able to be determined.

- 1929: Edwin Hubble - An astronomer focusing on the stars, Hubble came about the age of the Universe, not just the Earth, from a different direction. Hubble noticed that distant galaxies were all moving away from us, producing a shift in the light patterns that we see here on Earth. This shift in the light patterns was termed the "red shift", based on the pattern that the star's light produces. He also noted that the further the galaxy is away from us, the faster it was moving away from us. He determined that all the galaxies were moving away from each other, and if all of the galaxies were moving away from each other, then at one point in time they would all have to have been in the same location. This led to the Big Bang Theory that states that the entire Universe started as a great explosion some time in the past. Looking at the rate at which the stars were moving led Hubble to estimate that the age of the Universe was 2 billion years old. This was a problem, given the dates that have already been produced for the age of the Earth at the time were similar, if not older.

- 1941: Alfred Nier - Throughout the 1930's, Nier and his colleges determined that the different isotopes (isotopes are different weights of individual elements) of lead were produced from different sources. Some had no radioactive sources and others were produced by different isotopes of Uranium or Thorium, all of which have different half-lives. This allowed researched to determine the age of a rock just based on the average abundances of the different Lead isotopes. Using this information Nier produced an age of 2.57 Ga from the oldest known rock at the time, the Huran Claim Monzanite.

- 1946: Arthur Holmes and F.G. Houtermans - Holmes and Houtermans expanded upon Nier's research and developed plots showing how these Lead-Lead percentages could be used to calculate out the age of the Earth. From this information they were able to date the age of the Earth back 3.35 Ga.

- 1950's: Reevaluations of Hubble's luminosities in the 1950's corrected for Hubble's age dates, giving current astronomers an age range of 10-20 billion year age for the Big Bang. Which was a much longer time than the current estimated range for the age of the Earth. Many scientists were happy about this because it is difficult to find a case where the Universe could be younger than the Earth. Further refinements have narrowed that range to ~13.8 billion years for the Age of the Universe, based on improvements in the determination of this rate of expansion (space.com).

- 1953: Clair Cameron Paterson - While trying to figure out the age of the Earth, it had been determined that the oldest rocks on Earth were a problem to find. Over time the Earth eats its older rocks producing newer rocks, leaving fewer and fewer really old rocks behind. So, over time, the amount of rocks from the origins of the Earth became rare to the point of non-existent. It was also determined that if the Earth and the Solar System formed at the same time, then the date of the oldest material in the solar system would be the same as the age of the Earth. So scientists started looking outside the Earth for rocks that formed elsewhere. The perfect place to look came in the guise of meteorites, extraterrestrial rocks located right here on Earth. C.C. Paterson proceeded to calculate the age of the Earth using several different meteorites across the planet. Using the Lead-Lead age dating technique developed earlier, he determined an age for the Earth at 4.5 Ga. This is an age that has since been confirmed, and refined, by many other scientists using many other methods.

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Possible Educational Activity

Calculation for the age of the Earth is obviously not limited to just Good Omens, it is a geological theory that has been around for some time and knowing the scientific age of the Earth is frequently a fact given out in grade school. However, the determination of that age is often overlooked by many people and I am sure there are not many people who can tell the process by which the age of the Earth was finally discovered, or even who was the scientist credited with the calculation. So for an educational assignment I suggest having people look up several of the people associated with calculations for the age of the Earth, what processes did they use, what were their limiting factors, and what assumptions were made that may limit their calculation's validity.  

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References
https://answersingenesis.org/bible-timeline/the-world-born-in-4004-bc/
https://www.scientificamerican.com/article/how-science-figured-out-the-age-of-the-earth/
http://large.stanford.edu/courses/2016/ph241/caballero2/
http://www.talkorigins.org/faqs/geohist.html
https://www.atnf.csiro.au/outreach/education/senior/cosmicengine/hubble.html
Faure, Gunter. "Principles of isotope geology, second edition." (1986).

Tuesday, October 01, 2019

DINOSAURS!: From Cultural to Pop Culture - 1930: The Sinclair Dinosaur

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1930: The Sinclair Dinosaur


For anyone that has driven around the western United States and had an eye out for dinosaurs they have likely seen a statue of the Sinclair Dinosaur outside of Sinclair Oil stations or other gas stations that sell Sinclair Oil (such as Holiday Gas). 
A fiberglass Apatosaurus by the name of DINO in front of a Sinclair near Dinosaur, CO

The dinosaur, with the apropos name of DINO, was first introduced as the Sinclair mascot in 1930 and quickly became very popular with it being registered as a trademark in 1932. 

 Some of the original advertisement with DINO on it for Sinclair oil.
Upon creation for the logo, the dinosaur was originally referred to as a Brontosaurus, however scientific consensus since that time determined that the Brontosaurus was more correctly to be called an Apatosaurus. This is because they were deemed to be the same animal and the Apatosaurus was named first, hence the name takes priority. Recent research however has cast that into doubt and the name of "Brontosaurus" may yet again be a valid name (Tschopp et al., 2015). It is unknown if Sinclair is going to change DINO back though.

Following the success of DINO, the dinosaur started to appear in more locations. In the 1960's fiberglass installations of DINO began to appear at Sinclair Oil stations, a tradition that still continues today. I personally love the fact that this particular DINO we found had a saddle attached. This made for perfect photo opportunities to be sure.



Not only was DINO introduced around the country in the form of fiberglass models but it began showing up in the Macy's Thanksgiving Day Parade in 1963. And although he stopped attending in 1976, he thankfully began again in 2015. 

DINO from the 2018 Macy Thanksgiving Day Parade
DINO from the 2018 Macy Thanksgiving Day Parade


I would be remiss if I didn't point out that despite the popular assumption that oil comes from dinosaurs (hence the use of a dinosaur as a symbol of an oil company being a smart move), oil doesn't actually come from dinosaurs. As was pointed out in a previous Geology Fact...
Despite the common misconception, most fossil fuels do not actually come from dinosaurs or fossils for that matter. Oil and natural gas formed mostly from bacteria that died and blanketed the bottom of the sea before being buried and “cooked” into the fossil fuels we all know and love. 


References

Tschopp E, Mateus O, Benson RBJ. 2015A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda) PeerJ 3:e857 

Wednesday, August 21, 2019

Random Geology Pictures - The 2017 Solar Eclipse

In my ever present attempt to be right on top of things, I am only now able to post about my attempt to document the August 21st, 2017 solar eclipse. I figured since today was the two year anniversary of the event, I would take that as a cue to get this up. I should start off by noting: you NEVER look at a solar eclipse straight on. It can burn out your eyeballs (or something to that effect), so you want to have a work around. Either a solar filter or a pinhole camera (as described below) work best.

Overall, I have been getting better at taking pictures of the eclipses and that is partially because I have been using better equipment. Here are my previous attempts (if you scroll through all my "Eclipse" tags).

I started off by buying a solar filter for my camera. A cheap alternative to buying a whole solar lens. And although it may not have been perfect, I think it actually worked really well for a fraction of the price.

Here is our Canon DSLR all rigged up with the solar filter.

Don't worry, we also had our Solar Sunglasses. Here is my daughter checking out the eclipse with me.

Selfie with my glasses and the sun at the start of the eclipse.

They worked really well, but taking pictures through them was a bit difficult.

One thing to note about the Solar Eclipse. There are ways to watch the eclipse where you make a pinhole camera. Basically put a small hole through a cardboard box and on the bottom of the box you can see the eclipse as the moon moves across the sun. Trees actually do the same exact thing, since the gaps between the leaves act as millions of tiny little pinhole cameras. So if you have a leafy tree nearby you can actually see this phenomenon played out a thousand fold in the shadows.





I went and took pictures of the eclipse every 10 minutes to try and get a full progression of shots. What ended up happening was then I was able to line them all up and show a really good time-lapse of the event. Since I live down in Utah, I was slightly off the "full eclipse" line but we still ended up getting about 80-90% coverage.

 Here is the eclipse towards the beginning.

Here is the eclipse about mid-way.

And here is the eclipse on the back half.

 And here is my complete time-lapse of the event. 


So, all in all, not a bad outcome.

Wednesday, April 03, 2019

Paleo in Pop Culture - The Bronx Zoo

Paleo in Pop Culture

Within the walls of one of the buildings at the Bronx Zoo, there is the "preserved" skull of a crocodile. Although likely carved or casted in the concrete, it still intrigued me. They made it look so much like a fossil that I wanted to know what it was. And for the longest time I was not sure of the specific species of crocodile, although I assumed it was at least an extant (currently living) species. I come to find out one of my friends, Domenic D'Amore, a Vertebrate Anatomy Professor at Daemen College, knows a bit about crocodiles and I asked him for his take on the image. His answer seems to be the magic answer: Tomistoma, the false gharial. 

Carving in the concrete at the Bronx Zoo. Assumed to be Tomistoma

The Tomistoma is a freshwater crocodile that is native to Indonesia, Malaysia, Brunei, and Thailand. They generally live in rivers, lakes, and swamps, but prefer low lying areas of land. They have a varied diet that ranges from fish and lizards to even cattle in some recorded instances. The Bronx Zoo actually has some Tomistoma crocodiles named Elvis and Priscilla, which have been with the zoo since 1988. The Tomistoma is noted for its narrow snout and very sharp teeth. 


The Tomistoma is classified as Vulnerable with less than 10,000 known individuals known to exist in the wild.

Elvis and Priscilla. Tomistoma crocodiles at the Bronx Zoo. Photo courtesy of WCS.

References

Monday, March 25, 2019

Geology of the National Parks Through Pictures - DeSoto National Memorial

My next post about the Geology of the National Parks Through Pictures  from a recent trip to visit my mother in Florida. I managed to convince the family to hit up the nearby national 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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DeSoto National Memorial

 The obligatory entrance sign with my Gummy Bear.

 The park sits at the mouth of Tampa Bay along the south shore of the Manatee River. This is an estuary environment where the salt water from the Gulf of Mexico mixes with the fresh water from the Manatee River.

The ecological environments within this small park range from beach front dune to mangrove swamp.

 But with many archeological parks, one of the primary geological aspects are the building stones used to make the dwellings. Here we have the remains of the "Tabby House". Tabby is a building stone made from the mixture of oyster shells, lime, sand, and water creating a hardened stone brick over about three days. The bricks were then coated in a plaster of lime, sand, and water.

 A view over DeSoto Point overlooking the Manatee River.

 Here is a shell midden, which is essentially a garbage pile of discarded remains of mollusks, shellfish, and bones. You can see within this midden the rather large gastropod (snail) shells.

 Another geological aspect commen in many parks are the building stones used in monuments. Here is a view of the Holy Eucharist Monument. The base of the monument is limestone cut in Mankato, Minnesota. The limestone in use is the Ordovician age Kasota limestone, which is actually a dolomitic limestone, part of the Oneota dolomitic strata. The color of the stone is known as a "buff color" which is that slightly reddish-brown color due to the 1% iron oxide composition providing a rust staining to the stone. Although the Kasota does not have many fossils, it does have a significant number of traces fossils running through the rock, however I am not certain the type of trace fossils preserved.

The carving stone came from Madrid, unfortunately I cannot find any information about the type of stone used, nor did I take any better pictures or get a closer look at the stone to determine for myself.

 Taking a stroll though the dense beach forest.

 The Desoto Trail marker, using "granite" from an unknown location.

A closer view of the "granite", but based on this picture it may more accurately be described as a diorite, however I don't recall what type of rock it was from my visit.

References

Friday, March 22, 2019

Geology of the National Parks Through Pictures - Canaveral National Seashore

My next post about the Geology of the National Parks Through Pictures is about a park visited a long time ago.




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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Back a long time ago during a Spring Break trip of 2003, my girlfriend (at the time) and I hit up the Canaveral National Seashore. And although the pictures taken at the time weren't geologically inclined, there is still geology that abounds. The seashore is made up of several geological features, mainly a barrier island beach and the sheltered lagoon, which provides an safe space for the wildlife in the region, properly termed an estuary. 

The barrier island, as seen here with me attempting to enter the Atlantic Ocean, is a protective sand beach environment that breaks up the waves before they can hit the mainland. This beach, detached from the mainland, is created by the inward movement of the waves interacting with the outward movement of the waves, also known as the riptide. At this location where the waves interact, the ability of the water to carry sediment out to sea is reduced and the sand drops to the ocean floor. Over time this sand piles up, eventually becoming an island strip that acts as a barrier to the ocean waves and provides a safe and quiet lagoon between the island and the mainland. Canaveral National Seashore provides 24 miles of undeveloped beach, the longest continuous stretch in all of eastern Florida.

Although not directly geological, as a paleontologist I am also a biologist at heart and so the ecology, the fauna, and the flora of different parks also interests me. Here we have several instances of the fauna of the park with the first being an armadillo. We actually encountered quite a few of these guys, much more than I had ever seen before or since.

Checking out the beach at night allowed me to find some crabs scuttling along.

And some of my favorite wildlife, the manatees. The lagoon provides a perfect habitat for them, protecting them from the strong ocean waves and providing them with a redible supply of food.

Monday, March 11, 2019

Geology of the National Parks Through Pictures - The Washington Monument

My next post about the Geology of the National Parks Through Pictures is about some parks visited a long time ago within Washington D.C.




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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 View from Arlington National Cemetery. Like many of Washington D.C.'s monuments and memorials, there are multiple stones that were used for the construction of the Washington Monument.

1. Underneath it all is the foundation, which is comprised of the District's official rock, the Potomac Bluestone. Potomac bluestone is a more archaic term of the rock unit currently known as the Sykesville Formation, a formation that has had numerous designations over its history. The Sykesville Formation is identified as a metagreywacke, which is a metamorphosed greywacke. This type of rock is a poorly sorted, course and angular grained, sandstone or conglomerate. Greywackes typically are formed in the deep marine from strong turbidity currents (underwater landslides). The metagreywackes of the Sykesville Formation contain various degrees of metamorphism and in many places original sediment and sedimentary structures can still be identified within the rock unit itself. The earliest stones quarried by settlers of the region were the schists and gneisses of the Piedmont, known locally as this Potomac Bluestone. The Potomac Bluestone, or Sykesville Formation, lies towards the northwest of Washington D.C., crossing the Potomac River. This region contains many heavily metamorphosed and faulted rock units and these rocks are thought to have been metamorphosed from Neoproterozoic to Early Cambrian diamictites and sedimentary melanges, which contained a wide range of rocks. The Sykesville Formation was likely being metamorphosed from the Ordovician into the Silurian. The rock itself is a light- to medium-grey medium-grained metagreywacke melange consisting of a quartz, feldspar, and a large mixture of pebble and boulder sized chunks of unmetamorphosed rocks (termed olistoliths). The Sykesville has a fracture pattern along the foliation plane and two mutually perpendicular joint sets. This fracture pattern results in the landscape breaking into a series of pyramidal protrusion that aided in the the use as an early building stone for the District. Quarries along Rock Creek and Little Falls in Maryland provided Sykesville blocks for many early Washington D.C. projects.

 2. The outer layer of the Washington Monument is constructed of three different types of marble. The bottom 152 feet are built with "Texas Marble", named for the quarry in which it was mined in Texas, Maryland. However, the geological name for the marble is the Cockeysville Marble. The Cockeysville Marble is Late Precambrian (~600 million years old) in age and has many variations and layers within it making individual quarries of the marble contain significantly different rock types. The variations within the marble amount to differences in the amount of magnesium within the rock, where some areas have a metadolostone (high Mg content) versus a metalimestone (high Ca, low Mg content) varieties of marble. The Texas Quarry produces a course-grained marble that is a nearly pure calcitic marble (a high Ca metalimestone).

Following the initial portion of construction (1848-1854) the funds ran out for the project and the monument construction was stopped. This is where the color change takes place.


View across the Tidal Basin.

3. Construction resumed 25 years later after discovering the foundation needed to be increased and repaired. Four rows of new marble were then added to the monument above the Texas Marble. This marble is the Sheffield Marble from the John A Briggs' quarry in Sheffield, Massachusetts. A slight color change can be observed at this point, however since the layers are so minimal compared to the size of the monument, it may be unobserved. The Briggs' Quarry marble is geologically known as the Early Ordovician, Stockbridge Marble. The marble is a white calcite marble interbedded with light grey dolostone.

After significant delays and problems obtaining the Sheffield Marble, the contract was canceled and the builders went back to the original stone, or at least as close as they could get to it.

4. Above the color change line encompassing the upper 2/3rds of the monument is a repeat of the Cockeysville Marble, however this time it is quarried from the Beaver Dam Quarry in Cockeysville, Maryland. The Cockeysville mine is located 1.5 miles from the Texas, Maryland mine where the lower section of the monument's marble is from. When the monument was being constructed the marbles were nearly identical and therefore it was assumed that everything would match. However, weathering has treated the two marbles differently, despite being from the same formation and from nearly the same quarry. This is because of the heterogeneity of the marble listed above. The marble at Cockeysville is finer-grained and has a much higher Mg content, more akin to a metadolostone. The smaller grain size and the increase in magnesium content results in the weathering producing a slightly different color for the marble over time, a feature that is pronounced when displayed on the scale of the Washington Monument.



5. Behind the marble outer face are also multiple stones. One of the backing stones for the marble facade is red Seneca Sandstone. Geologically the red Seneca Sandstone is known as the Poolesville Member of the Manassas Formation. This is the same rock that was used for the construction of the Smithsonian Castle. The Manassas sandstone is part of a series of Triassic sandstone basins that extend from North Carolina to Massachusetts. These related rocks supplied much of the "brownstone" used in the NYC construction at the same time. The sandstone is primarily composed of quartz, alkali feldspar, and muscovite with ~5% Fe2O3 concentration, attributing to the strong rusty-red color.

6. Another of the backing stones is the Maine Granite, which is from a quarry on Mount Waldo, Maine. The geological name for the granite, is surprisingly enough, the Mount Waldo Granite. The granite is a Devonian Age (390 million years old) intrusive igneous pluton. The pluton intruded within tightly folded Precambrian and Lower Paleozoic age schists, gneisses, quartzites, and migmatites. The granite is light to medium grey, course-grained, and porphyritic, which contains the minerals microcline, plagioclase, quartz, and biotite. The granite deposit was studied as a potential place for a shallow underground oil repository, however documentation of severe rockbursts have prevented the unit from being used as such.

The third of the marble facade backing stones is the previously mentioned Potomac Bluestone, which was also used as the foundational rock.

References

Saturday, March 09, 2019

Geology of the National Parks Through Pictures - The Jefferson Memorial

My next post about the Geology of the National Parks Through Pictures is about some parks visited a long time ago within Washington D.C.




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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The Jefferson Memorial


View from the front (circa 1990). Like the Lincoln Memorial, the Jefferson Memorial is comprised of at least seven different build stones from across the country.

1. The memorial itself is constructed of white Imperial Danby marble from Vermont. Imperial Danby marble is actually the Lower Ordovician, Columbian Marble member of the Shelburne Formation. The Shelburne Formation includes three different rock units; the Sutherland Falls marble, the Intermediate Dolostone, and the Columbian Marble. The Shelburne Formation formed from the metamorphism of Cambrian to Ordovician age limestones that were metamorphosed during the Early Ordovician. Located on Dorset Mountain in Danby, the Danby Quarry is the world's largest underground quarry and is one of the largest producers of marble in the world. The Columbian Member is roughly 500 to 600 feet thick and is a white, massive, medium-grained marble that is composed primarily of calcite. There are also small instances of pyrite, chalcopyrite, muscovite, and chlorite that give the marble some green or dark streaks. The marble usually weathers white, but can vary to dark grey. Due to the strong similarities between the Sutherland Falls Marble and the Columbian Marble, it is often difficult to differentiate between the two, but unlike the Sutherland, contorted forms are not conspicuous within the Columbian and the markings usually have a linear pattern.

2. The dome is constructed of Indiana limestone, also known as the Salem Formation and also used in the Lincoln Memorial. The Salem Formation is a Middle Mississippian age (335-340 million year old) light-grey to bluish-grey pure calcarenite limestone that crops out between Bloomington and Bedford in the south-central portion of Indiana. Quarrying of the stone began in 1827 and has continued up to the present day with nine different quarries all mining the same formation. Indiana Limestone is a "freestone", which means that there is no preferential cracking, jointing, or splitting. This also means that blocks of the limestone can be planed, hand-worked, or otherwise manipulated without fear of the rock breaking in a preferential direction. The limestone is 97% pure calcite with microscopic foraminifera and bryozoan fossils found throughout.


View from the top of the Washington Monument.

3. The foundation and circular terraces are made from Georgia granite. Despite the enormous amount of data regarding almost any other piece of stone in this memorial, or most of the other Washington D.C. memorials, there isn't much information regarding which "Georgia granite" was actually used in the construction of the memorial. My assumption (and it is only an assumption) is that the granite in question is the Elberton Granite. Elberton Granite is a "monumental grade" granite, meaning that the granite has a "uniform texture and color, freedom from flaws and general suitability for polishing and carving as well as resistance to weathering". It is also one of the few granites to be actively quarried in Georgia during the 1930's, when the Jefferson Memorial was constructed. Elberton Granite is part of the Lexington-Oglesby Blue Granite Belt that extends southwest past Lexington, over an area 25 miles long and 15 miles wide. The granite has a blue-grey appearance and is predominantly made up of three minerals, white felspar, greyish quartz, and the black flecks of biotite. The Elberton granite formed from an igneous intrusion within the Georgia Inner Piedmont region of eastern Georgia during the Mississippian, ~320 million years ago.


4. The interior walls of the memorial are constructed of white Georgia marble that is also used in the Lincoln Memorial. Although there are several different "varieties" of marble within Georgia, they all seem to be variations of the same marble deposit, Murphy Marble. The Murphy Marble Belt runs from North Carolina down through Georgia and centers on Tate, Georgia, where the Georgia Marble Company mines the marble. It is the Georgia Mining Company that provided the marble for the Lincoln statue. The specific variety of marble for the Lincoln statue comes from the Cherokee White Quarry, which is mixed in among folded gneisses and schists within the Murphy Marble Belt. The Cherokee White Marble is a partly dolominitic but nearly pure calcite marble. These marbles have been extensively quarried since 1840. The Murphy Marble started off as a Lower Cambrian limestone that was eventually metamorphosed and folded numerous times during the lower Paleozoic from the Middle Ordovician through the Early Mississippian.

4. The floor is made of Tennessee Pink Marble. Also used in the Lincoln Memorial, the Tennessee Pink Marble is interesting in that it actually isn't a marble, it is a limestone, meaning it was never metamorphosed like the Yule Marble. The "marble" even includes such sedimentary structures as cross bedding, bryozoan fossils, crinoid fossils, and stylolites. The stone 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.


The bronze statue of President Jefferson

6. The statue of Jefferson is composed of bronze and rests on a black Minnesota granite. Like the "Georgia Marble" listed above, there are no specific references for the "black Minnesota granite", especially considering that granite is very rarely, if ever, found "black". The best assumption I can make about which building stone was used for this (without seeing the rock in person) is that the pedestal is actually composed of a gabbro. Gabbro, like granite, is a course grained, intrusive, igneous rock, so in essence they will have a similar appearance. Unlike granite though, gabbro is composed of mostly dark colored minerals without any quartz, unlike granite which has mostly light colored minerals and is predominantly quartz (a light colored translucent mineral). Within the state of Minnesota, the main gabbro being quarried at the time of the construction is the Duluth Gabbro Complex. The Duluth Gabbro Complex began intruding into the Minnesota host rocks approximately a billion years ago during the Late Precambrian. The Complex is made up of several different rock types from repeated igneous intrusions over a ~200 million year time span. These rock types include anorthositic gabbro, normal gabbro, ferogranodiorite, and granophyre. The oldest rock of the complex is the anorthositic gabbro, which is made up of 75-90% the mineral labradorite, a black colored mineral, making this a very black rock indeed. It is my hypothesis that the Jefferson pedestal is composed of this anorthositic gabbro (until I am able to get more information).

7. The statue of Jefferson also has a gray Missouri marble ring surrounding the base. Similar to the Tennessee Pink Marble above, the Missouri Marble not really a marble, but a limestone. One of the ways that this can be identified is the presence of fossils and stylolites, both of which would have likely been destroyed if the rock were to be metamorphosed. Unfortunately the specific rock used in the Memorial is not identified and limestone is found all across the state of Missouri. However, the Missouri state capital building used limestone in its construction and it was noted that once the interior limestone was polished, it gained the distinction of being called "marble". Based on the time period of the Capital Building's construction (1915-1917) and this common misnomer of the rock, I feel that the same rock was used for the Jefferson Memorial. The Capital interior stone is known as "Napoleon Gray marble" and can be found not only in the state capital but also in the NY Stock Exchange and the Legion of Honor: The Fine Arts Museum in San Francisco. The Napoleon Gray is more commonly known as Phenix Limestone, from the nearby town of Phenix, or geologically it was called the Burlington and Keokuk limestones. These limestones (the Burlington and Keokuk) are difficult to differentiate and are typically grouped together as part of the Osagean Series. The Burlington and Keokuk limestones formed during the flooding of North America 325-360 million years ago during the Early Mississippian. This flooding produced a shallow inland sea, called the Kaskaskia Sea, which allowed for the deposition of many fossils including crinoids, brachiopods, corals, and bryozoans. 

View of the Memorial from across the Tidal Basin. From this angle you can see straight through the memorial.

References