Wednesday, April 07, 2021

Geological Destination - Monument Valley Tribal Park

Back in November of 2019, while driving back from Arizona to the wife to do one of her Iron Man races, we drove through one of the Navajo Nation Tribal Parks, Monument Valley Tribal Park. As a runner, my wife wanted to get a shot of her running up the Forest Gump hill, while as a geologist, I just like looking at the pretty rocks.

Slightly downhill from us but essentially the same view in Forest Gump

As can be seen in the image, this is easily an icon geological location. The rock units within Monument Valley are essentially the same as the rock units within the nearby Canyon de Chelly National Monument, however the landscape is a bit different. Instead of the rocks being isolated within a canyon system like at the park, they are now elevated above the surrounding landscape. This is likely an effect of the Colorado Plateau, where this region had been slightly elevated compared to the areas further down south. A breakdown of the rock units within each of the mesas seen in the background is as follows:

Monument Valley geology. Image courtesy of the UGS.

The Shinarump, is part of the Chinle Formation, a Late Triassic (~225 million years old) yellow-grey river-deposited sandstone and conglomerate. 

Below the Shinarump is the Moenkopi formation. The Moenkopi Formation is an Early to Middle Triassic formation (~245 million years old) that is is predominantly made up of the reddish-brown shale. The Moenkopi was deposited within an intertidal environment, with alternating sea levels producing thinly bedded layers of mud (shale) and sand (sandstone). 

Below the Shinarump is the De Chelly Sandstone. The De Chelly Sandstone is a Permian age (~200 million years old) aeolian sandstone. Aeolian means that it is formed by blowing wind, in particular sand dunes, or a desert environment. When sand dunes are frozen in time, such as when they become rocks, and eroded you can see features termed cross-bedding. These rock preserve an ancient sand sea desert, known as an erg, that used to be located here. Sandstones are also frequently extremely hard rocks that are resistant to weathering. When they weather, they fracture into regular joints. Those are the vertical line patterns of the rocks as seen in the image above. It is also what produces the shear-walled rock mesas as we know them today. 

Below the De Chelly Sandstone, is the more erodible Organ Rock Shale. You can tell it erodes much more easily by the smooth slope that forms from the edge of the overlying sandstone. If the sandstone wasn't there to protect the shale, the shale would have eroded long ago. The Organ Rock Shale is another Permian formation (~270 million years old), that mainly comprised of mudstone (shale) and siltstones. They were deposited by streams within a tidal flat environment. The Organ Rock Shale then underlies much of the surrounding landscape which is then covered over with much, much younger (Quaternary) sediment (known as alluvium) transported in by winds and water from these and other surrounding rock formation.

Tuesday, April 06, 2021

Geology and Paleontology in Pop Culture - The Mote Marine Laboratory and Aquarium

 Back in August of 2019, I was able to go visit my mother in Florida without the threat of doom and on the trip we visited the local Mote Marine Laboratory and Aquarium in Sarasota. The Mote is broken up into several buildings over a nice campus with some great animal displays within it. But, as always, my focus tends to be drawn to geology and paleontology of the place. 


The Mote Marine Laboratory and Aquarium sits on the Lido Key, off the western coast of Florida within the Gulf of Mexico. The most notable geological thing that I found was the building stone that was surrounding one of the larger shark tanks. 

Here is a little bit of a zoomed out shot of the building stone. A closer look below will reveal what type of building stone we are looking at.

As we can see by the clearly coral fossils in this part of the rock, this is a limestone. Brain coral in particular here. There are many types of limestones based on what they are made up of. The term limestone just means that the rock is primarily composed of the calcium carbonate, typically in the form of the mineral calcite. Calcite can form in a few different ways, but the most common way is through the processes of marine organisms like the making of clam shells or coral skeletons. 

The different building blocks within the shark tank enclosure have some variety with what types of fossils are visible. Within this block we can see some shells, which are mostly up of some gastropods (snail) and bivales (like clams). 

A close up of some more coral.

And more coral. This piece is interesting because the upper left piece of coral and the lower right piece of coral are the same type of coral, just cut at different angles.

When identifying limestones, there a couple of different classifications that are used. Since this is clearly a reef rock, based on the presence of so much corals, that is what we want to focus on. 

Limestone classification of reef rocks. Image courtesy of SEPM.

My knowledge of limestone classifications is definitely limited, however based on the structure of the corals within the rock, they appear to be "autochthonous", which means that they had not been transported before they were turned into a rock. All of the above limestone pictures also probably don't fit into the same category, however I would say the majority of the blocks likely fall into the Framestone or Bafflestone category of limestone. 

On the coastal islands, there isn't much, if any, building stone localities so these must have been trucked in from somewhere, however I can't find any mention of specifically where they came from. They did likely originate locally due to the large abundance of coral reef limestones within the state of Florida. 


There are a few paleontological themed areas of the aquarium as well. This includes the "Fossil Creek" area, where people can get bags of sand filled with fossilized shark teeth. This area is highlighted by one of the most famous fossil sharks, the Otodus megalodon, more commonly just called the Megalodon.

A full sized rendering of what the Megalodon jaw would have looked like. However, only teeth of the Megalodon have ever been found so the entire jaw reconstruction is just that, a theorized reconstruction.

I love that in this version of the reconstruction they didn't even bother to hide the painterly strokes along the cartilage jaw.

Next to the Megalodon jaw there is also a couple of display cases with other fossil shark teeth including tiger, hammerhead, great white, mako, and of course the Megalodon. 

There are also some fossilized vertebrae, as well as other animal bits scattered throughout the cases.

I didn't take a picture of the identification sign, however I don't know if there even was one. But what interests me here, is that mixed among the mostly marine fossils are the teeth of a mammoth. Although there have been some mammoth discoveries in Florida (they aren't unheard of), just unexpected in a marine museum. 

These teeth, and other bones, may actually belong to a discovery of a nearby mammoth from Salt Creek, near Warm Mineral Springs, Florida back in 1987. 

Newspaper image of a pair of mammoth teeth found in 1987 from Salt Creek, Florida. Image courtesy of Warm Mineral Springs.

The newspaper listing of the find state an unknown age at the time of discovery, but that the fossils will likely be stored at the Mote Aquarium. 

And the last fossil I saw at the Mote is a vertebrae of whale tail found in southwestern Florida. 

Of course they also have modern skeletons on display. Here is the skeleton of a manatee.

And the skeleton of a giant sea turtle. 

Underside view of the sea turtle.

Monday, April 05, 2021

Geology Through Literature - Han Christian Andersen's: The Comet

Geology Through Literature: 

Hans Christian Andersen's: The Comet (1869)

And we have finally reached the ninth and final entry of Hans Christian Andersen's geological references.

For other Geology Through Literature entries, please check them out compiled on my website.

The Comet (1869)

Now there came a comet with its shiny nucleus and its menacing tail. People from the great castles and people from the poor huts gazed at it....

But a little boy and his mother still stayed inside their room. The mother believed ... that her son would soon die. The little boy lived many more years on earth. Indeed he lived to see the comet return sixty years later.


"This is the time to look at the comet," cried their neighbors.... 

The boy saw the bright ball of fire, with its shining tail. Some said it was three yards long, while others insisted it was several million yards longsuch a difference.

In general a comet is is a body of ice, rock, and organic compounds that can be up to several miles in diameter. "Comets are thought to originate from a region beyond the orbits of the outermost planets. Scientists believe that gravitational perturbations periodically jar comets out of this population, setting these "dirty snowballs" on orbital courses that bring them closer to the Sun. Some, called long-period comets, are in elliptical orbits of the Sun that take them far out beyond the planets and back. Others, called short-period comets, travel in shorter orbits nearer the Sun" (

Comet 153P/Ikeya-Zhang which has the longest known tail at over a billion kilometers. Image courtesy of NewScientist.

Although many comets are known to have a return period, much of the comets with known return periods had only been discovered fairly recently. There are two types of comets based on their orbital periods; known as long-period comets, which are comets with orbital periods greater than 200 years, and short-period comets, with orbital periods less than 200 years. Even the short-period comets can be broken up into Halley-Type comets, which have orbital periods between 20 and 200 years, and Jupiter-family comets, that have orbital periods less than 20 years. 

Besides Halley's comet, which was determined in 1705 by Edmund Halley to return at a set amount of time (75-76 years), there aren't many comets that have been identified with periodic return periods. To date, only ~300 periodic comets have been identified, with less than 10 identified by the publication of this story (1869). 

The problem with identifying these comets is that typically only bright comets are easily identified in the sky, especially by the naked eye. These bright comets, often called "Great Comets", however usually need to be fairly large, pass closely to the sun, and pass closely to earth. Although these bright comets are bright enough to be seen by the human eye, their close approach to the sun often can spell disaster for the comet, reducing it to space dust. So many of the Great Comets are one time affairs. Halley's Comet being the exception of a bright comet that continues to have a periodic return.

Within the story Andersen seemed to take the appearance of a bright comet and a periodic comet and mixed them with his own tale of a man that would live another 60 years. To date there is only one comet with an approximate return periods of 60 years, and that was only discovered in 2015. This comet, C/2015 F5 (SWAN-XingMing), has a return period of 60.9 years and was only barely visible due to its mostly lack of a tail. 

The Great Comet of 1861 as painted by E. Weiss. Image courtesy of Wikipedia

The Great Comet of 1861 (C/1861 J1) would probably be the closest great comet to the time of publication. Although, as I said that many of the Great Comets are destroyed, it appears that this comet was linked with other pervious comets and had been determined to have an orbit of 407 years. As more time passes and more of the historical records are analyzed it will likely come that even more of the previously thought one-off comets will be determined to be linked, and/or have a periodicity themselves.

Andersen makes note of the length of the comet tail, in which I assume is a difference between looking at in in the sky (three yards long) and thinking of it in its real life length (several million yards long). In real life, the tail is created when solar winds and solar radiation pressure blows ionized gasses and debris off of the comet. This causes the tail to always be pointed away from the sun. Since the tail is a product of the sun, the closer to the sun that the comet gets, the longer and brighter that the tail gets. And there are actually two tails on a comet, the blue tail is formed from the ionized gasses blowing off the comet ball while the white/pink tail is from the small dust particles. 

Typical visible comets can get a tail that can reach up to 150 million kilometers, much more than even the high-end length noted in the story. And as can be seen in the top picture here, the length of the tail can even get to over a billion kilometers in length. 

Sunday, April 04, 2021

Geology Through Literature - Han Christian Andersen's: The Rags

Geology Through Literature: 

Hans Christian Andersen's: The Rags (1868)

We continue on to the eighth, and penultimate entry, of Hans Christian Andersen's geological references.

For other Geology Through Literature entries, please check them out compiled on my website.

The Rags (1868)

Bedrock Geology
"I am Norse!" said the Norwegian. "And when I've said I'm Norse I guess I've said enough. I'm firm of fiber, like the ancient granite rocks of old Norway. The land up there has a constitution, like the free United States. It makes my fibers tingle to think what I am and to sound out my thoughts in words of granite!"

 Norway's bedrock is truly ancient by no exaggeration of the term. The oldest rocks in Norway are part of the Fennoscandinavian shield, which are the Scandinavian Precambrian bedrock, the oldest rocks of which can be found along the northern edges of the country in Finnmark, Troms, and Vesterålen. These oldest rocks date back almost 3 billion years old.

The oldest rock in Norway at 2.9 billion years old. Image courtesy of the Geological Survey of Norway.

As you can see in the map below, most of these truly ancient parts of the Scandinavian shield are in the Finland and Russian parts of the Fennoscandian Peninsula. 

Bedrock geology of Scandinavia. Image courtesy of the Geological Survey of Norway

The vast majority of Norway is underlain by incredibly old rocks, even those parts not in the northernmost regions. The question now is, are these rocks truly granites like the text says? Granite is often a term used as an all encompassing term for crystalline rocks. Just look at the countertop industry where everything is "granite" where much of the counter tops are not actually granite by the geological definition of the word. 

Granite is an intrusive igneous rock that formed from the cooling of magma deep within the earth where the earth insulated the magma allowing to cool slowly. The slow cooling allowed the mineral crystals within the rock the time to grow creating the crystalline rock so well known as granite. The naming of an igneous rock is dependent on how the rock formed (intrusive versus extrusive) and what the mineral composition is, essentially how much quartz is there in the rock. To identify the rocks there is a chart/scale of intrusive igneous rocks which are identified based on the silica (quartz) content. 

Basic Intrusive Igneous Rock Scale 

On the high end of the scale with a high quartz/silica content is Granite, known as a felsic rock. In the middle, with an intermediate amount of quartz/silica, is Diorite. And on the low end of the scale with no quartz/silica is Gabbro and Peridotite. Igneous rocks with no silica are known as mafic rocks.

Really old rocks also have more instances where they can get metamorphosed. This means that they had been subject to increased heat and/or pressure. When that happens, the minerals within the rock change. The rocks don't fully melt, but the increased heat allows the elements within the rock to reorganize themselves forming new rocks. When granite is metamorphosed, it produces a metamorphic rock known as a gneiss (pronounced "nice"). Gneiss is the rock most often miscategorized as a granite, since they so often resemble one another, however there is a mineralogical and a structural difference between the two. 

Portion of the Geological Map of the Fennoscandian Shield showing northern Norway. Circled rocks represent the oldest (Archaean rocks identified as "462") in Norway. Image courtesy of GigaPan.

Looking at a much more detailed geological map in the Fennoscandinavian shield, it turns out that oldest rocks within the Norwegian portion of the shield are indeed composed of granites and gneisses. The northernmost coastal rocks in Norway are identified on the geological map of the region as "462", these are Archaean granite, granodiorite, tonalite, and metamorphic equivalents. The other rocks of similar age are identified as "463", and these are migmatitic gneiss of granodioritic to dioritic composition. 

Being so old, the rocks only represent the basement of the region and have several billion years of rock history deposited on top of them. They record the history of mountains built up, eroded down, built up again, and eroded down again. There is more history in these basement rocks than most rocks will ever see in their lifetime before they are broken down by the passage of time. So, like Andersen said, the northern portions of Norway really do contain "ancient granite rocks".

Saturday, April 03, 2021

Geology Through Literature - Han Christian Andersen's: Vano and Glano

Geology Through Literature: 

Hans Christian Andersen's: Vänö and Glänö (1867)

For the seventh entry we continue on through Hans Christian Andersen's oeuvre to our next geological reference.

For other Geology Through Literature entries, please check them out compiled on my website.

Vänö and Glänö (1867)

Shoreline Geology

Near the coast of Zealand, off Holsteinborg castle, there once lay two wooded islands, Vänö and Glänö, on which were villages, churches, and farms. The islands were quite close to the coast and quite close to each other; now there is but one of these tracts remaining.

One night a fierce tempest broke loose. The ocean rose higher than ever before within man's memory. The storm increase; it was like doomsday weather, and it sounded as id the earth were splitting...

That night Vänö vanished into the ocean depth; it was if that island had never existed. But afterward on many a summer night, when the still, clear water was at a low tide, and the fisherman was out on his boat to catch eel by the light of a torch, he could, on looking sharply, see Vänö, with its white church tower and high church wall, deep down below.


You went away from there ... and after a few years you have returned.... Where is Glänö? You don't see little wooded island before you; you see only open water. Has Vänö finally taken Glänö, as it so long was expected to? On what stormy night did this happen, and when did an earthquake move old Holsteinborg so far inland?

There was no stormy night; it all happened on cleat sunny days. Human skill built a dam to hold back the ocean; human skill dried up the water and bound Glänö to the mainland. The bay has become a meadow with luxuriant grass; Glänö has become part of Zealand. 

If you try and search for the word "Glänö", most of the results are just for references to this specific story. However, I was able to find a bit for information after doing a search for the Holsteinborg castle, which does exist. 

Google Maps of Holsteinborg Castle showing Glænø Island.

Based on the map of the castle, there sure enough appears to be an island, directly next to Holsteinborg Castle called Glænø. I feel this is far too close a coincidence to be happenstance. However, in the story, it specifically states that the island of Glänö was dammed up and incorporated into the mainland. Even though the map above doesn't appear that the island is not an island, let's look at the aerial photo to see if things get any clearer. 

Aerial Photo of the area around Holsteinborg Castle. Image courtesy of Google Earth

Here we can see a lot more sediment build up in the estuary behind the island, and that is because of the dam that is built to the island. In the picture here and above, the road that leads to the island on the northwest corner is on top of a 100 meter long dam. So, as the story stated, the residents built a dam, essentially merging the island with the mainland.

But where could Vänö (also spelled Vænø) be then?

There are a couple of theories that I have. My first theory is that the island directly next to Glænø, Østerfed could be a new name for the island. However, since this is clearly still an island, my guess is that this is not what we are looking for.

If this is not Vänö, then the island must once have resided within the bay to the south of Glænø called  Smålandsfarvandet. If we look a bit further out from Glænø into the bay, there is an island with a similar sounding name.

Smålandsfarvandet aerial image courtesy of Google Earth.

The island, Vejrø, does have a similar name, however based on the description, the island is not really "quite close", nor "near the coast". It is also not a sunken island. So, my last theory is that the island truly was sunk off the coast somewhere. But if it was, there is likely evidence in the bathymetry of the bay. There should be some sort of raised island under the water, as other parts of the text describe that the island is still visible on calm water days.

Although there are not a lot of publicly available bathymetry charts of Smålandsfarvandet, I did find a few that offered glimpses that there is a submerged land area about halfway between Glænø and Vejrø. As can be seen in the following bathymetry chart. 

Bathymetry map off the southern shore of Glænø. Image courtesy of Kroon et al., 2015.

A little further investigation and it turns out this shallower area of the bay on the southern edge of the map above is actually a reef. It is known as the Kirkegrund Reef and parts of the reef reach as low as 1-2 meters below sea level (~5 feet). 

Cross section of the Kirkegrund Reef. Image courtesy of Stæhr et al., 2016.

The cross section above shows shallow areas around 6 meters below sea level, however other maps show a significantly shallower region in other parts of the reef. The further back in time that we go, the lower sea level was, so perhaps this was the island that Andersen was referring to. If we think that this island was once Vänö, then it is possible that legends grew up about this island off the coast that eventually was swallowed up by a big storm. And the things that the fishermen were seeing off shore was actually the reef far below the surface and not the remnants of various buildings once build on the island.

Friday, April 02, 2021

Geology Through Literature - Han Christian Andersen's: The Ice Maiden

Geology Through Literature: 

Hans Christian Andersen's: The Ice Maiden (1861)

For the sixth entry we continue on through Hans Christian Andersen's oeuvre to our next geological reference.

For other Geology Through Literature entries, please check them out compiled on my website.

The Ice Maiden (1861)


They had made the greater part of the journey, had climbed the highest ridges to the snowfields and could already see her native valley with the familiar scattered cottages; they now had only to cross the upper part of one great glacier. The newly fallen snow concealed a crevasse, not deep enough to reach the abyss below where the water rushed along, but deeper than a man's height... 

The glacier lies like a rushing stream, frozen and pressed into blocks of green crystal, one huge mass of ice balanced on another; the swelling stream of ice and snow tears along in the depths beneath, while within in it dwells the Ice Maiden, queen of the glaciers. 

Glaciers are essentially as Andersen describes them, big piles of ice that slowly move across the landscape. Mountain glaciers in particular are known for flowing down valleys, like rivers. In the upper part of the mountains, where it is colder, snow builds up over time. As more and more snow is dropped on the top of the mountain, eventually it starts to get compacted in the vertically lower layers, forming ice. As more and more ice builds up, the glacier starts to flow, like molasses, down the valleys. As the glacier moves down the valleys, the ice picks up and freezes small and large pieces of rocks and drags them along on the bottom of the ice. These rock fragments then grind down into the bedrock over which the glacier flows. Eventually the glacier reaches an elevation where it is too warm for the ice to remain frozen all of the time (like in the upper regions) and it starts to melt. Towards the end of the glacier where all of it has melted away, it acts like a conveyor belt, carrying all of the debris it eroded away and piling it up into one big pile of glacial debris called a moraine. 

Glacial meltwater pathways. Image courtesy of Antarctic Glaciers

Due to differences in temperature from the upper surface of the glacier and the bottom depths, the upper layers will sometimes melt from warming by the solar rays. This occurs even in the coldest of temperatures due to the ability of the sun's energy to melt the ice. This melted water then flows down into the glacier through large cracks in the ice known as crevasses. This meltwater will sometimes then flow all the way to the base of the glacier along the bedrock where streams can be formed.  

Snow covered crevasse. Image courtesy of SwissEduc.

Also as the glacier moves, the whole glacier may not always flow as one solid, cohesive unit. Going over uneven terrain, or variations in the width of the valley, will alter how the glacier flows. These flow changes then have the potential to crack the ice. These cracks are known as crevasses, and sometimes the crevasses can go from the surface all the way to the base of the glacier, which in some instances could be hundreds to thousands of feet thick. These crevasses are also often covered over with a thin layer of snow due to variations in movement of the ice. These thin crusts, or bridges, of snow make walking across the surface of a glacier a very dangerous thing to do if you don't know what you are doing.


Thursday, April 01, 2021

Geology Through Literature - Han Christian Andersen's: A Story from the Sand Dunes

Geology Through Literature: 

Hans Christian Andersen's: A Story from the Sand Dunes (1859)

For the fifth entry we continue on through Hans Christian Andersen's oeuvre to our next geological reference.

For other Geology Through Literature entries, please check them out compiled on my website.

A Story from the Sand Dunes (1859)

Shoreline Erosion
Still, it is easy to imagine yourself back in times more remote than even the reign of Christian VII, for now, as then, the brown heath of Jutland stretches for miles with its barrow, its mirages, its winding, rough, sandy roads. To the west, where broad streams flow into the fjords, there are marshes and meadows, encircled by the high sand hills which rise up toward the sea like an Alpine chain with jagged summits, broken only by high banks of clay. From these the waves eat off giant mouthfuls year after year, so that the edges and summits topple down as though shaken by an earthquake. That's how it looks today, and that's how it looked many years ago...

 The passage describes the persistent erosion along the western shore of Jutland, a region of Denmark, with Western Jutland bordering the North Sea. 

Map of Jutland, Denmark. Image courtesy of Wikitravel.

The beaches and the sand dunes of the Jutland coast were deposited during the last Ice Age consisting of clay and fine sand that total 100 meters of sediment deposited over 100,000 years. These deposits are known as the Skærumhede series.

The Jutland western shore. Image by Lucia Margheritini and courtesy of Science Nordic.

These sediments make up much of the western coast, but they are slowly being transported out to sea due to coastal erosion. As the cliff faces are worn away at the bottom, the upper layers eventually collapse and then are carried away by the waves. Much of the erosion occurs during the winter months when the water levels are higher and storm levels are stronger, producing winds and waves capable of wearing away at the cliff face that is otherwise out of reach during calm, summer days. 

The sediment along the coast is then transported through the longshore current from south to north. However, the amount of sediment removed is more than the sediment supplied by the current, so the coastline is in a losing scenario. It is estimate that it has been in a losing scenario since the last ice age, ~10,000 years ago. 

And although this erosion has been continuing since long before and after Andersen's time, the current rate of erosion has been increasing. There are several reasons for this but mainly they can boil down to manmade impacts and climate change. Structures on the beach, scientists know, have a tendency to alter the erosion patterns, often producing more erosion in areas beyond where the structure are built. Think dams and sea walls. These structures stop erosion where they are built, but the lack of sediment within the water beyond these points allows for more erosion than would otherwise occur. With climate change there are many reasons for potentially accelerated erosion including: more and/or stronger storms, rising sea levels, and changes in weather patterns. It is estimated in this region that the changes in weather patterns, specifically more rain, has been the cause of the accelerated erosion, with the increased rain breaking down the cliff edges more readily than they were before.