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11.3: Fossils - Geosciences

11.3: Fossils - Geosciences


Throughout human history, people have discovered fossils and wondered about the creatures that lived long ago. The griffin, a mythical creature with a lion’s body and an eagle’s head and wings, was probably based on skeletons of Protoceratops that were discovered by nomads in Central Asia (Figure 11.1).

Figure 11.1: Griffin (left) and Protoceratops (right).

Another fossil reminded the Greeks of the coiled horns of a ram. The Greeks named them ammonites after the ram god Ammon. Similarly, legends of the Cyclops may be based on fossilized elephant skulls found in Crete and other Mediterranean islands. Can you see why (Figure 11.2)?

Figure 11.2: Ammonite (left) and elephant skull (right).

Many of the real creatures whose bones became fossilized were no less marvelous than the mythical creatures they inspired (Figure 11.3). The giant pterosaur Quetzalcoatlus had a wingspan of up to 12 meters (39 feet). The dinosaur Argentinosaurus had an estimated weight of 80,000 kg, equal to the weight of seven elephants! Other fossils, such as the trilobite and ammonite, impress us with their bizarre forms and delicate beauty.

Figure 11.3: Kolihapeltis sp (left) and Ammonite (right).

Lesson Objectives

  • Explain why it is rare for an organism to be preserved as a fossil.
  • Distinguish between body fossils and trace fossils.
  • Describe five types of fossilization.
  • Explain the importance of index fossils, and give several examples.
  • Describe what a living fossil is.

How Fossils Form

A fossil is any remains or trace of an ancient organism. Fossils include body fossils, left behind when the soft parts have decayed away, as well as trace fossils, such as burrows, tracks, or fossilized waste (feces) (Figure 11.4).

Figure 11.4: Coprolite (fossilized waste or feces) from a meat-eating dinosaur.

The process of a once living organism becoming a fossil is called fossilization. Fossilization is a very rare process: of all the organisms that have lived on Earth, only a tiny percentage of them ever become fossils. To see why, imagine an antelope that dies on the African plain. Most of its body is quickly eaten by scavengers, and the remaining flesh is soon eaten by insects and bacteria, leaving behind only scattered bones. As the years go by, the bones are scattered and fragmented into small pieces, eventually turning into dust and returning their nutrients to the soil. It would be rare for any of the antelope’s remains to actually be preserved as a fossil.

Figure 11.5: Fossil shell that has been attacked by a boring sponge.

On the ocean floor, a similar process occurs when clams, oysters, and other shellfish die. The soft parts quickly decay, and the shells are scattered over the sea floor. If the shells are in shallow water, wave action soon grinds them into sand-sized pieces. Even if they are not in shallow water, the shells are attacked by worms, sponges, and other animals (Figure 11.5).

For animals that lack hard shells or bones, fossilization is even more rare. As a result, the fossil record contains many animals with shells, bones, or other hard parts, and few softbodied organisms. There is virtually no fossil record of jellyfish, worms, or slugs. Insects, which are by far the most common land animals, are only rarely found as fossils. Because mammal teeth are much more resistant than other bones, a large portion of the mammal fossil record consists of teeth. This means the fossil record will show many organisms that had shells, bones or other hard parts and will almost always miss the many soft-bodied organisms that lived at the same time.

Because most decay and fragmentation occurs at the surface, the main factor that contributes to fossilization is quick burial. Marine animals that die near a river delta may be buried by sediment carried by the river. A storm at sea may shift sediment on the ocean floor, covering and helping to preserve skeletal remains.

On land, burial is rare, so consequently fossils of land animals and plants are less common than marine fossils. Land organisms can be buried by mudslides or ash from a volcanic eruption, or covered by sand in a sandstorm. Skeletons can be covered by mud in lakes, swamps, or bogs as well. Some of the best-preserved skeletons of land animals are found in the La Brea Tar Pits of Los Angeles, California. Although the animals trapped in the pits probably suffered a slow, miserable death, their bones were preserved perfectly by the sticky tar.

In spite of the difficulties of preservation, billions of fossils have been discovered, examined, and identified by thousands of scientists. The fossil record is our best clue to the history of life on Earth, and an important indicator of past climates and geological conditions as well. The fossil record also plays a key role in our lives. Fossil fuels such as coal, gas, and oil formed from the decayed remains of plants and animals that lived millions of years ago.

Types of Fossils

Fossilization can occur in many ways. Most fossils are preserved in one of five processes (Figure 11.6): preserved remains, permineralization, molds and casts, replacement, and compression.

Preserved Remains

The rarest form of fossilization is the preservation of original skeletal material and even soft tissue. For example, insects have been preserved perfectly in amber, which is ancient tree sap. Several mammoths and even a Neanderthal hunter have been discovered frozen in glaciers. These preserved remains allow scientists the rare opportunity to examine the skin, hair, and organs of ancient creatures. Scientists have collected DNA from these remains and compared the DNA sequences to those of modern creatures.

Permineralization

The most common method of fossilization is permineralization. After a bone, wood fragment, or shell is buried in sediment, it may be exposed to mineral-rich water that moves through the sediment. This water will deposit minerals into empty spaces, producing a fossil. Fossil dinosaur bones, petrified wood, and many marine fossils were formed by permineralization.

Molds and Casts

In some cases, the original bone or shell dissolves away, leaving behind an empty space in the shape of the shell or bone. This depression is called a mold. Later the space may be filled with other sediments to form a matching cast in the shape of the original organism. Many mollusks (clams, snails, octopi and squid) are commonly found as molds and casts because their shells dissolve easily.

Replacement

In some cases, the original shell or bone dissolves away and is replaced by a different mineral. For example, shells that were originally calcite may be replaced by dolomite, quartz, or pyrite. If quartz fossils are surrounded by a calcite matrix, the calcite can be dissolved away by acid, leaving behind an exquisitely preserved quartz fossil.

Compression

Some fossils form when their remains are compressed by high pressure. This can leave behind a dark imprint of the fossil. Compression is most common for fossils of leaves and ferns, but can occur with other organisms, as well.

Figure 11.6: Five types of fossils: insect preserved in amber, petrified wood, cast and mold of a clam shell, compression fossil of a fern and pyritized ammonite.

Exceptional Preservation

Some rock beds have produced exceptional fossils. Fossils from these beds may show evidence of soft body parts that are not normally preserved. Two of the most famous examples of soft organism preservation are the Burgess Shale in Canada and the Solnhofen Limestone in Germany. The Burgess Shale is 505 million years old and records the first explosion of shelled organisms in Earth’s oceans. Many of the Burgess Shale fossils are bizarre animals that seem unrelated to any other animal group. The Solnhofen Limestone is 145 million years old and contains fossils of many soft-bodied organisms that are not normally preserved, such as jellyfish. The most famous Solnhofen fossil is Archaeopteryx, one of the earliest birds. Although it resembles a dinosaur fossil, impressions of feathers can clearly be seen (Figure 11.7).

Figure 11.7: Fossils from Lagerstätten: Archaeopteryx (left) and Anomalocaris (right). Archaeopteryx was an early bird. Anomalocaris was an enormous predator (one meter long) that lived 500 million years ago.

Index Fossils and Living Fossils

The fossil record shows clearly that over time, life on Earth has changed. Fossils in relatively young rocks tend to resemble animals and plants that are living today. In older rocks, fossils are less similar to modern organisms.

As scientists collected fossils from different rock layers and formations, they discovered that they could often recognize the rock layer by the assemblage of fossils it contained. Some fossils proved particularly useful in matching up rock layers from different regions. These fossils, calledindex fossils, are widespread but only existed for a relatively brief period of time. When a particular index fossil is found, the relative age of the bed is immediately known.

Many fossils may qualify as index fossils. Ammonites, trilobites, and graptolites are often used as index fossils, as are various microfossils, or fossils of microscopic organisms. Fossils of animals that drifted in the upper layers of the ocean are particularly useful as index fossils, as they may be distributed all over the world.

In contrast to index fossils, living fossils are organisms that have existed for a tremendously long period of time without changing very much at all. For example, the Lingulata brachiopods have existed from the Cambrian period to the present, a time span of over 500 million years! Modern specimens of Lingulata are almost indistinguishable from their fossil counterparts (Figure 11.8).

Figure 11.8: Fossil Lingula (left) and modern Lingula (right).

Clues from Fossils

Fossils are our best form of evidence about the history of life on Earth. In addition, fossils can give us clues about past climates, the motions of plates, and other major geological events.

The first clue that fossils can give is whether an environment was marine (underwater) or terrestrial (on land). Along with the rock characteristics, fossils can indicate whether the water was shallow or deep, and whether the rate of sedimentation was slow or rapid. The amount of wear and fragmentation of a fossil can allow scientists to estimate the amount of wave action or the frequency of storms.

Often fossils of marine organisms are found on or near tall mountains. For example, the Himalayas, the tallest mountains in the world, contain trilobites, brachiopods, and other marine fossils. This indicates that rocks on the seabed have been uplifted to form huge mountains. In the case of the Himalayas, this happened when the Indian Subcontinent began to ram into Asia about 40 million years ago.

Fossils can also reveal clues about past climate. For example, fossils of plants and coal beds have been found in Antarctica. Although Antarctica is frozen today, in the past it must have been much warmer. This happened both because Earth’s climate has changed and because Antarctica has not always been located at the South Pole.

One of the most fascinating patterns revealed by the fossil record is a number of mass extinctions, times when many species died off. Although the mass extinction that killed the dinosaurs is most famous, the largest mass extinction in Earth history occurred at the end of the Permian period, about 250 million years ago. In this catastrophe, it is estimated that over 95% of species on Earth went extinct! The cause of these mass extinctions is not definitely known, but most scientists believe that collisions with comets or asteroids were the cause of at least a few of these disasters.

Lesson Summary

  • A fossil is any remains of ancient life. Fossils can be body fossils, which are remains of the organism itself or trace fossils, such as burrows, tracks, or other evidence of activity.
  • Preservation as a fossil is a relatively rare process. The chances of becoming a fossil are enhanced by quick burial and the presence of preservable hard parts, such as bones or shells.
  • Fossils form in five ways: preservation of original remains, permineralization, molds and casts, replacement, and compression.
  • Rock formations with exceptional fossils are called very important for scientists to study. They allow us to see information about organisms that we may not otherwise ever know.
  • Index fossils are fossils that are widespread but only existed for a short period of time. Index fossils help scientists to find the relative age of a rock layer and match it up with other rock layers.
  • Living fossils are organisms that haven’t changed much in millions of years and are still alive today.
  • Fossils give clues about the history of life on Earth, environments, climate, movement of plates, and other events.

Review Questions

  1. What factors make it more likely that an animal will be preserved as a fossil?
  2. What are the five main processes of fossilization?
  3. A scientist wants to determine the age of a rock. The rock contains an index fossil and an ancient relative of a living fossil. Which fossil will be more useful for dating the rock, and why?
  4. The island of Spitzbergen is in the Arctic Ocean north of Norway, near the North Pole. Fossils of tropical fruits have been found in coal deposits in Spitzbergen. What does this indicate?

Vocabulary

amber
Fossilized tree sap.
body fossil
The remains of an ancient organism. Examples include shells, bones, teeth, and leaves.
cast
A structure that forms when sediments fill a mold and harden, forming a replica of the original structure.
fossil
Any remains or trace of an ancient organism.
fossil fuel
A fuel that was formed from the remains of ancient organisms. Examples include coal, oil, and natural gas.
fossilization
The process of becoming a fossil.
index fossil
A fossil that identifies and shows the relative age of the rocks in which it is found. Index fossils come from species that were widespread but existed for a relatively brief period of time.
living fossil
A modern species or genus that has existed on Earth for millions of years without changing very much.
marine
Of or belonging to the sea.
mass extinction
A period of time when an unusually high number of species became extinct.
microfossil
A fossil that must be studied with the aid of a microscope.
mold
An impression made in sediments by the hard parts of an organism.
permineralization
A type of fossilization in which minerals are deposited into the pores of the original hard parts of an organism.
terrestrial
Of or belonging to the land.
trace fossil
Evidence of the activity of an ancient organism. Examples include tracks, trails, burrows, tubes, boreholes, and bite marks.

Points to Consider

  • What are some other examples of mythical creatures that may be based on fossils?
  • Why is it so rare for an animal to be preserved as a fossil?
  • Some organisms are more easily preserved than others. Why is this a problem for scientists who are studying ancient ecosystems?
  • Why are examples of amazing fossil preservation so valuable for scientists?
  • Many fossils of marine organisms have been found in the middle of continents, far from any ocean. What conclusion can you draw from this?

Oldest fossils ever found show life on Earth began before 3.5 billion years ago

Researchers at UCLA and the University of Wisconsin–Madison have confirmed that microscopic fossils discovered in a nearly 3.5 billion-year-old piece of rock in Western Australia are the oldest fossils ever found and indeed the earliest direct evidence of life on Earth.

An epoxy mount containing a sliver of a nearly 3.5 billion-year-old rock from the Apex chert deposit in Western Australia is pictured at the Wisconsin Secondary Ion Mass Spectrometer Lab (WiscSIMS) in Weeks Hall. Photo: Jeff Miller

The study, published Dec. 18, 2017 in the Proceedings of the National Academy of Sciences, was led by J. William Schopf, professor of paleobiology at UCLA, and John W. Valley, professor of geoscience at the University of Wisconsin–Madison. The research relied on new technology and scientific expertise developed by researchers in the UW–Madison WiscSIMS Laboratory.

The study describes 11 microbial specimens from five separate taxa, linking their morphologies to chemical signatures that are characteristic of life. Some represent now-extinct bacteria and microbes from a domain of life called Archaea, while others are similar to microbial species still found today. The findings also suggest how each may have survived on an oxygen-free planet.

An example of one of the microfossils discovered in a sample of rock recovered from the Apex Chert. A new study used sophisticated chemical analysis to confirm the microscopic structures found in the rock are biological. Courtesy of J. William Schopf

The microfossils — so called because they are not evident to the naked eye — were first described in the journal Science in 1993 by Schopf and his team, which identified them based largely on the fossils’ unique, cylindrical and filamentous shapes. Schopf, director of UCLA’s Center for the Study of Evolution and the Origin of Life, published further supporting evidence of their biological identities in 2002.

He collected the rock in which the fossils were found in 1982 from the Apex chert deposit of Western Australia, one of the few places on the planet where geological evidence of early Earth has been preserved, largely because it has not been subjected to geological processes that would have altered it, like burial and extreme heating due to plate-tectonic activity.

But Schopf’s earlier interpretations have been disputed. Critics argued they are just odd minerals that only look like biological specimens. However, Valley says, the new findings put these doubts to rest the microfossils are indeed biological.

“I think it’s settled,” he says.

Using a secondary ion mass spectrometer (SIMS) at UW–Madison called IMS 1280 — one of just a handful of such instruments in the world — Valley and his team, including department geoscientists Kouki Kitajima and Michael Spicuzza, were able to separate the carbon composing each fossil into its constituent isotopes and measure their ratios.

Isotopes are different versions of the same chemical element that vary in their masses. Different organic substances — whether in rock, microbe or animal ­— contain characteristic ratios of their stable carbon isotopes.

Using SIMS, Valley’s team was able to tease apart the carbon-12 from the carbon-13 within each fossil and measure the ratio of the two compared to a known carbon isotope standard and a fossil-less section of the rock in which they were found.

“The differences in carbon isotope ratios correlate with their shapes,” Valley says. “If they’re not biological there is no reason for such a correlation. Their C-13-to-C-12 ratios are characteristic of biology and metabolic function.”

John Valley, professor of geoscience, is pictured in his office in Weeks Hall. Photo: Jeff Miller

Based on this information, the researchers were also able to assign identities and likely physiological behaviors to the fossils locked inside the rock, Valley says. The results show that “these are a primitive, but diverse group of organisms,” says Schopf.

The team identified a complex group of microbes: phototrophic bacteria that would have relied on the sun to produce energy, Archaea that produced methane, and gammaproteobacteria that consumed methane, a gas believed to be an important constituent of Earth’s early atmosphere before oxygen was present.

UW–Madison geoscience researchers on a 2010 field trip to the Apex Chert, a rock formation in western Australia that is among the oldest and best-preserved rock deposits in the world. Courtesy of John Valley

It took Valley’s team nearly 10 years to develop the processes to accurately analyze the microfossils — fossils this old and rare have never been subjected to SIMS analysis before. The study builds on earlier achievements at WiscSIMS to modify the SIMS instrument, to develop protocols for sample preparation and analysis, and to calibrate necessary standards to match as closely as possible the hydrocarbon content to the samples of interest.

In preparation for SIMS analysis, the team needed to painstakingly grind the original sample down as slowly as possible to expose the delicate fossils themselves — all suspended at different levels within the rock and encased in a hard layer of quartz — without actually destroying them. Spicuzza describes making countless trips up and down the stairs in the department as geoscience technician Brian Hess ground and polished each microfossil in the sample, one micrometer at a time.

Each microfossil is about 10 micrometers wide eight of them could fit along the width of a human hair.

Valley and Schopf are part of the Wisconsin Astrobiology Research Consortium, funded by the NASA Astrobiology Institute, which exists to study and understand the origins, the future and the nature of life on Earth and throughout the universe.

“The Apex fossils are scrappy. Hard to find. Difficult to study. They are abundant but charred, shredded, overly cooked. Tiny bits and pieces are common but generally nondescript short two-or-three-celled fragments are rare and easy to overlook many-celled specimens are few and far between and fossils that could be called ‘well-preserved’ — like those of the Gunflint and Bitter Springs deposit — are nonexistent. Were these remnants not so remarkably ancient they would not merit much attention.”
—J. William Schopf, “Cradle of Life”

Studies such as this one, Schopf says, indicate life could be common throughout the universe. But importantly, here on Earth, because several different types of microbes were shown to be already present by 3.5 billion years ago, it tells us that “life had to have begun substantially earlier — nobody knows how much earlier — and confirms it is not difficult for primitive life to form and to evolve into more advanced microorganisms,” says Schopf.

Earlier studies by Valley and his team, dating to 2001, have shown that liquid water oceans existed on Earth as early as 4.3 billion years ago, more than 800 million years before the fossils of the present study would have been alive, and just 250 million years after the Earth formed.

“We have no direct evidence that life existed 4.3 billion years ago but there is no reason why it couldn’t have,” says Valley. “This is something we all would like to find out.”

UW–Madison has a legacy of pushing back the accepted dates of early life on Earth. In 1953, the late Stanley Tyler, a geologist at the university who passed away in 1963 at the age of 57, was the first person to discover microfossils in Precambrian rocks. This pushed the origins of life back more than a billion years, from 540 million to 1.8 billion years ago.

“People are really interested in when life on Earth first emerged,” Valley says. “This study was 10 times more time-consuming and more difficult than I first imagined, but it came to fruition because of many dedicated people who have been excited about this since day one … I think a lot more microfossil analyses will be made on samples of Earth and possibly from other planetary bodies.”

The research was supported by the NASA Astrobiology Institute at the University of Wisconsin–Madison and the Center for the Study of Evolution and the Origin of Life at UCLA. WiscSIMS is supported by the National Science Foundation (EAR-1355590) and UW–Madison.


Wyoming Fossils: Coming to Grips with the Absurdity of the Flood Geology Model of Fossil Origins

The sedimentary rocks of the Earth hold vast quantities of fossils. Hundreds of years of careful observations have shown that fossils are far from random in their distribution but rather they appear in the geological column in a distinct pattern or order referred to as fossil succession. How can we explain the observed distribution of fossils in the geological column?

One attempt to explain the origin and observed distribution of fossils comes from young-earth creationists (YECs). The young-earth view proposes that much or most of the thousands of feet of fossil bearing rocks—and the fossils themselves—that make up the world’s land masses were deposited during a single catastrophic world-wide flood approximately 4350 years ago. In reference to that Flood, Ken Ham and other YECs are fond of asking:

If there really was a Flood, what would the evidence be? Billions of dead things, buried in rock layers, laid down by water, all over the earth. After which Ken Ham continues: Well, that is exactly what we see – billions of dead things, buried in rock layers, laid down by water, all over the earth!

Ken Ham is right about one thing. There are billions of dead things buried in sediments laid down in water although this is a vast underestimate of the number of fossils. But how long was required to preserve all these fossils, how did it happen and how might we be able to discern these past events?

YEC Global flood proponents have proposed three possible mechanisms to explain the observed succession of fossils in the geological column: 1) Hydrodynamic sorting, 2) Differential escape, and 3) Ecological zonation. None of these general proposals hold water when fossils and their geological context are examined in detail.

I have already provided numerous examples of the utter inadequacies of hydrodynamic sorting including my articles about diatoms (Life in a Glass House: Diatoms shatter young earth flood geology), forams (Diatoms and Forams: Testing the Young Earth Flood Geology Hypothesis) and my article in Perspectives on Science and Christian Faith (Flood Geology’s Abominable Mystery). Recently, differential escape seems to have fallen out of favor in YEC circles for good reason. It required that organisms running away from the Flood were preserved in the fossil record as a result of the organisms differing abilities to escape (eg. birds are higher up in the fossil record than the amphibians etc…). Any close examination of the fossil record will quickly dispel this as a viable hypothesis.

A typical argument of ecological zonation/sorting in the fossil record because of successive drownings of ecosystems during the onset of a global flood. This one is from Harold Coffin in “Origin by Design” from 1983.

The last mechanism – ecological zonation/sorting – has maintained its popularity among YECs. YECs recognize that fossils are not randomly distributed in rocks with respect to the types of fossils found in any particular fossil formation. For example, usually fossils in a layers of rock are either marine or terrestrial in origin. They propose that groups of fossils representing ecological communities would have been preserved in the fossil record such that deep ocean, shallow sea and then terrestrial fossils might be found as one moves up the geological column (see figure to the right). However, why and how these might be stacked directly on top of one another in the geological column is not at all clear.

Most of the YEC’s audience is unfamiliar with the fossil record knowing it only from museums and movies. Ken Ham’s description of fossils and simplistic models of a massive flood sweeping organisms to a quick death and preservation sound plausible to those unfamiliar with the fossil evidence. So it may be a natural reaction among many followers or young earth creationism to wonder, why don’t scientists recognize the evidence of a single great catastrophe in earth’s history?

To illustrate one reason scientists do not consider the YEC model even plausible I want to take you on a trip to Wyoming and show you a portion of the fossil record. I tell people that they go and look at fossils for themselves and ask: how did these particular fossils come to be in the place they are today? A global flood doesn’t provide a realistic or even possible explanation for most of the fossils they will see. Those who have spent time collecting fossils and examining the geological context of where they are found quickly realize that flood geology models fall well short of providing any plausible mechanisms for explaining the observed distribution of fossils.

Until you are able to plan your own fossil observation excursion to witness this for yourself, I will do the next best thing and take you to some fossil sites that I visited not long ago. I will provide some details about the locations were they are found and what kinds of rock they are found. After we have made some observations we can ask the question: What is the best explanation for the origins of these fossils? Were they all laid down in a recent global flood or deposited over long periods of time in a shallow sea?

Short Summary: Fossils are found in discrete units of the geological column. They are typically found in natural ecological assemblages rather than random collections of ecologically unrelated species. The fossils described here were not deposited over a short period of time by hydrodynamic sorting, differential escape or ecological zonation. The communities of fossils found in central Wyoming are best explained as the product of long periods of accumulation in alternating shallow seas, tidal flats and beaches caused by changes in sea level and continental uplift over time. These preserved communities of organisms are not a chaotic assemblage nor are they sorted by size or mass. These communities are stacked on top of each other therefore not the result of zonation in the pre-Flood world. These fossils, like billions of others, demonstrate that young-earth flood geology is void of explanatory power and thus not a viable working hypothesis.

All of the locations I am going to take you are places that I found myself along with my family on summer vacation. I hiked many miles in the badlands of the Bighorn Basin in Wyoming. On those hikes I looked for fossils and took pictures and samples at places where I found them. I have already shared pictures of several of these locations and some of the fossils that I found (see links in discussion below). Here I want to share a few more fossil sites that I found and compare multiple fossil locations.

Below I provide an overview of the fossil locations and then I examine what we can learn from the fossils in Wyoming about the history of the earth.

Above I note on this Google map screenshot the approximate location of places were I collected Jurassic Period fossils in June of 2016. There is an additional sight just below the map east of Worland. The distance between the furthest locations is about 40 miles apart. All of these locations had multiple species of fossils.

Let’s take a quick look at some of these sites.

Site 1: Sheep Mountain, Wyoming

I shared many pictures from this site before (see: Hiking through the Jurassic Period in Wyoming). Below is a picture I took that I have annotated to show where my sons and I collected fossils.

Below is a picture of the surface shown on the left side of the picture above. These are Gryphaea fossils which are a bivalve clam.

Below is a picture of the ground representing what we saw on the other side of the ravine in the first picture. These are fragments of a flat bivalve shell—not Gryphaeae —and remains—called Belemnites—of an extinct squid. In my post about hiking through the Jurassic I talked about these Belemnites in more detail.

Site 2: Red Gulch Region

Below is a picture I took after climbing a large hill overlooking the Red Gulch dinosaur trackway site. A few weeks ago I wrote about the Dinosaur tracks found here and the other fossils in the immediate vicinity (see: Walking in the Footprints of Giants). Just above the dinosaur tracks in hard limestone rock are several dozen feet of soft shales that are loaded with Gryphaea clam shells. In the picture below I have indicated the general area where Gryphaea fossils can be found in great abundance eroded out of the rock and sitting on the surface. As I climbed the hill above these rocks I encountered rock with no discernible (i.e. visible to the naked eye) fossils and then I came upon a portion of a hill-side that was covered with fossils.

Below is a picture of the hillside covered with pieces of bivalve shells and Belemnites. Does that sound familiar? I saw the same fossils in the same order at the location on Sheep Mountain but I was about 20 miles from that site here at Red Gulch.

Below is a closeup of some of the Belmnites on the surface of the side of the hill. I did not notice them at the time but there are also a couple of pieces of crinoid stems on the surface as well. Crinoids are animals that also lived in shallow seas and left behind copious numbers of fossils in the geologoical column.

Down the hill but just above the dinosaur tracks in the hard limestone we found many Grypheae fossils. In the picture below most of the layers of rock you see above the dinosaur tracksite have Gryphaea fossils. Here are a couple of my kids working to pick a few small ones out of Sundance Formation shales that make up the side of the hill.

On the flat surface just above where my kids are above, many more pieces of Gryphaea fossils can be found.

Site #3: Tensleep, Wyoming dinosaur region

Below Hyatsville, Wyoming we took a small side road and eventually reached a hill my van could not climb. We then hiked about two miles further west into the badlands. Eventually we worked our way up another hill and stumbled upon millions of shell fragments and Belemnites. The soil type and the fossils appeared the same as those I had seen at Red Gulch and Sheep Mountain but we were another 20 to 25 miles south of the Red Gulch site.

Below is a picture of the surface on the hillside showing abundant Belemnite fragments.

A closer image of the Belemnites in this region.

Below is another Belemnite but also abundant fragments of clams. These are the same type of clam shell fragments I found at Sheep Mountain, the Red Gulch area and near Shell, Wyoming.

Other sites: Shell, Wyoming and near Tensleep, Wyoming

Near Shell, Wyoming we found a hill with the same order of fossils. Grypheae fossils in the lower portion of the hillside and then some broken bivalve shells and Belmnites higher up on the hill side. Also, just west of the town of Tensleep, Wyoming I saw some Gryphaea fossils but at that location there was no higher ground since it had eroded away so there was no opportunity to see if the same Belemnites would have been in that area before it was eroded.

What did I observe and what can we learn from these fossils?

Fossils represent communities of organisms not a random assemblage of species: Where I found Gryphaea bivalve mussels they appeared as natural populations. There were large (2 inches) and tiny (<1/4 inch) complete shells and fragments of large and small shells. It is as if this was a shallow sea where a community of shells lived with old, young and deceased members all together. Separate from the layers of rock that contained these Gryphaea communities I found an abundance of different bivalve shells and Belemnites. Both of these fossils were represented by diverse sizes (1/4 inch to >5 inches) representing vast populations of each species. Since squid would have lived in the water column but the bivalves would have been living in the sediment there is no reason to expect to find these fossils together in a flood model which uses hydrodynamic sorting or differential escape to predict fossil distributions. Why would trillions of the same species of Gryphaea or Belemnite be preserved in one set of sedimentary rock but other species of the same kind of organism be found – according to other fossil hunters – in layers above and below these layers? In a chaotic worldwide flood how would massive populations including babies and adults all be swept together apart from billions of other specimens of a different species?

The same order of fossils can be observed over a hundred square miles: Without any foreknowledge of most of the fossils that I would find when I visited Wyoming I came across multiple locations up to 60 miles apart in which I found the same community of fossil types in the same stratigraphic order. In 30 to 50 feet of shale I found Gryphaea fossils and some crinoids and then there was rock above these which contained no visible fossils. Above that were another 30 to 50 feet of shale that contained abundant bivalve shells, Belemnites and a different species of crinoid. These observations are in contradiction to any hydrodynamic sorting explanation. Why would different species of crinoids which are the same size and approximate shape be separated into different layers with none found in a layer of rock in between? Why would Belemnites of every size only be found in one layer of shale and not found in the layers of shale below if all these layers of sediment were deposited in one large flood?

The fact that these communities of species can be found stacked on top of each other directly contradicts the ecological zonation/sorting hypothesis of flood geologists. At the same time hydrodynamic sorting and differential escape are nonsensical explanations for these fossils.

A far simpler explanation is that these fossils represent the remains of populations of organisms living in communities in a shallow sea for long periods of time. In this case, a plausible scenario includes: Gryphaea fossils living near shore were exposed to successive inputs of new sediment into that sea and the build of up small-bodied micro-organisms (eg. coccoliths) which gradually covered and preserved many shells. As sea levels rose, Gryphaea bivalves no longer found the area a good environment for survival and different communities of organisms arrived in the now deeper waters. Several different species of flat bivalves now took residence on the sea floor and squid swam in the shallow seas. As the squid died and their flesh decayed the hard rostrums collected on the sea floor along with the shells and were preserved. Later as the seas was filled with sediments and/or sea level fell the entire area was exposed to the air and now deposition of sediments from streams from the surrounding mountains continued to add new sediments on top of the marine sediments. These new sediments record footprints of dinosaurs, dinosaur bones and other terrestrial organisms.

The shale rock of the Bighorn Basin record for us an easily read history of the waxing and waning of a shallow sea not a chaotic global flood. Lest anyone think that maybe this is just the preservation of a pre-Flood environment as it was the day the Flood began, you should know that more than 6000 feet of additional sedimentary rock – mostly marine – is below the layers that we are concerned with today. Those rocks also contain fossils and so they had to all be deposited before these layers could be put down. How could a global flood deposit more than one mile of sediment and then have what appears to be deposits from a placid sea filled with just a few species of which somehow escaped being preserved before but then were ALL preserved at just this one moment in time?

Standing on a hillside in Wyoming with the evidence of the fossil record sitting right at your feet, the absurdity of the YEC flood geology model becomes all too clear.

The following amendment to Ken Ham’s saying is required: If the Earth really is millions of years old, what would the evidence be? Quadrillions of dead things, buried in rock layers, laid down by water, volcanic ash and landslides, all over the earth. Well, that is exactly what we see – quadrillions of dead things buried in rock layers laid down by water, volcanic ash, and landslides, all over the earth!

This article was originally written for and published on this site August 20, 2016


Experience the Fossil History of Colorado

Beneath a grassy mountain valley in central Colorado lies one of the richest and most diverse fossil deposits in the world. Petrified redwood stumps up to 14 feet wide and thousands of detailed fossils of insects and plants reveal the story of a very different, prehistoric Colorado.

Transcript

Life suited to a cool, temmperate climate flourishes here

But the world around us is constantly changing

Mountains rise and erode away

Life thrives and changes in a blink.

Our sense of time and the environment around us is grounded in the present

But our planet, its climate, and its communities of life have been changing for millions of years

Sometimes despite innumerable odds, a shadow of the past survives.

providing clues to ancient life that once existed in this very place.

The geology, fossils, and human stories of Florissant Fossil Beds National Monument are part of a common geologic heritage The layers of rock beneath this valley contain one of the richest fossil deposits in the world.

They hold clues of unexpected environments and life that existed here during a time called the late Eocene. dinosaurs were extinct,and it was now the age of mammals.

Around 37 million years ago

a distance explosion from a collapsing volcanic crater known as a caldera

sent an enormous flow of superheated ash and gas racing across the landscape like a volcanic hurricane

incinerating everything in its path

Slowly, life regained a foothold by 34 to 35 million years ago as new, powerful volcanoes loomed over the Florissant valley.

Periodic eruptions blanketed the valley with ash and debris.

Rainfall saturated the loose debris on the slopes of the volcano creating a massive fast moving mudflow called a lahar.

It was miles long and roughly fifteen feet tall when it reached the Florissant valley.

The slurry of mud and volcanic ash surrounded the bases of the towering redwoods.

As the redwoods died, their tops decayed away.

Groundwater, rich in dissolved silica from volcanic ash, gradually seeped into the wood, depositing minerals and petrifying it over time.

Volcanic eruptions continued over thousands of years

Another flowing lahar blocked a stream, creating the ancient Lake Florissant.

After several millennia this lake and the landscape surrounding it nourished an abundance of life.

Volcanic ash and clay settled on the lakebed creating layers of various thickness over time.

Single-celled algae called diatoms thrived in the mineral-rich water then died periodically.

The layers compressed and formed a thinly layered sedimentary rock called paper shale.

Leaves, seeds, insects, fish, and even birds settled to the bottom of the lake where they were buried by new layers of volcanic ash, clay, and diatoms.

Millions of years later, the shale holds fragile fossils, physical touchstones to ancient life, inspiring the mind with connections to this land and its past.

Shadows of ancient human history can also be found here, part of the shared geologic heritage of Florissant.

The Ute, Jicarilla Apache, and other tribes consider the area part of their ancestral lands.

Tribal members still have a strong connection to this area.

Paleontologists have been exploring the area since the 1870s

describing more than 1,800 species

making Florissant one of the richest fossil sites in the world.

Samuel Scudder conducted an excavation in the Florissant area in 1877, indentifying roughly 600 species.

Attracted by the Homestead Act of 1862, new settlers began estabishing ranches and farms in Florissant.

Charlotte Hill collected hundreds of important fossil specimens that she provided to scientists while homesteading and raising six children.

In gratitude, the fossil rose, Rosa Hilliae, was named after her.

Charlotte Hill collected one of the most remarkable fossil butterflies ever found, Prodryas persephone commonly known as a brush-footed butterfly.

Other brush-footed butterflies live in the Florissant ecosystem today.

Hundreds of new species of fossil plants, insects, spiders, and vertebrates were described as a result of Hill's work with scientists.

The shear number of fossils on the site made an impression on paleontologists like Theo Cockerell, who arrived in 1906.

COCKERELL: There has accumulated and almost embarassing amount of material, and many remarkable things have been discovered.

NARRATOR: Florissant fossils were sent to museums around the world, and the site became famous.

Tourists arrived eager to see the giant petrified stumps and to collect fossils as souveniers.

Dynamite was used to better expose the petrified stumps.

An attempt was even made to saw the big stump into pieces to ship to the 1893 World's Fair in Chicago.

Broken saw blades from the effort still remain.

Colorado Midland Railway allowed passengers to disembark at Florissant and collect fossils.

By the 1920s, tourists were beckoned by commercial sites and a dude ranch with a fireplace made from petrified wood.

SINGER: Now at one time, there were big petrified stumps and logs lying on the ground all around the countryside

but they have mostly been sold or stolen away.

NARRATOR:Paleontologist Harry MacGinitie began studying Florissant's fossils in the 1930s.

He saw the Florissant fossil area as key to understanding the story of life's past.

But years of uncontrolled collecting, had led to the increasing disappearance of the fossils.

Scientific and local communities began to call for conservation of the fossil beds.

In 1969, land containing fossils at Florissant was targeted for housing development.

The fossils and their clues to ancient life could be lost forever.

Scientists like Estella Leopold and other citizens formed a group called the Defenders of Florissant.

Paleobotanists MacGinitie joined Leopold and others to testify before Congress

and then brought senators to see Florissant first hand

MacGinitie: The land is not of particularly great value for housing or agriculture, but as a page of Earth's history it is priceless.

LEOPOLD: How can man evaluate his planetary environment and visulaize his historic place in it if he does not keep and cherish a few touchstones from the past?

NARRATOR: in a landmark environmental case, a legal team went to court to stop the imminent destruction of Florissant's fossils and their record of ancient life.

YANNACONE: To sacrifice this 34 million year old record for 30 year mortgages and basements is like wrapping fish with the Dead Sea Scrolls.

Narrator: On August 20, national monument status was granted to Florissant Fossil Beds, safeguarding it's geologic heritage for the world.

Some of the largest petrified stumps on the planet that onced faced bulldozing and dynmaite are now protected and monitored for any damage from the environment or weather.

It is estimated that some of these trees were over 230 feet tall and over 500 to 750 years old.

Florissant has the only known petrified trio, interconnected trunks growing as one plant.

The national monument paleontology staff and university partners conduct ongoing research

and work to stabilize and conserve fragile shale fossils and petrified stumps

keeping it possible for future scientists to study the fossils with new methods

so that they can reveal even more knowledge of the past.

Countless fossils are only visible under a microscope.

Millions of pollen grains, diatoms,and microscopic invertebrates are preserved at Florissant.

Microfossils are critical to understanding habitat, water quality, and climate here 34 million years ago.

By compaing Florissant's fossils to modern plants scientists can determine temperature and precipitation from the ecosystems of the ancient past.

Right after the end of the warm Eocene, there was a huge drop in global temperature.

The Florissant climate changed abruptly to a cooler temperature climate.

Plants native to the warmer climate either adapted, became extinct, or dispersed to warmer regions.

Fossils reveal to scientists how plants and animals responded to climate change in the past.

Modern relatives of the golden rain tree are native only to China, Taiwan, and Fiji

yet they once existed at Florissant milions of years ago.

The two most common plant fossils are extinct members of the elm and beech families.

Fossils of more than 30 species of vertebrates have been found.

The largest vetebrates were brontotheres, giants weighing two tons and standing eight feet tall.

Fish skeletons and mammal teeth are the most abundant.

Rare bird fossils have visible feathers captured in stone.

Florissant is especially noted for its delicate insect and spider fossils.

Fossil plants show evidence of damage from insects similar to today.

Delicate fossil butterflies and moths are very rare. Florissant has more species of these ,perhaps than any other fossil site in the world.

This extremely rare tsetse fly is evidence of a different climate that once existed at Florissant.

The tse tse fly now live only in tropical Africa

For ancient life, temperature changes occurred over tens of thousands of years

Some life became extinct some adapted to the changing climate and environment.

And some dispersed to other places where the climate was more favorable.

Climate change is happening today at a much more rapid rate

Florissant fossils allow us to look to the past to better understand the present.

and to guide our stewardship of life in the future.

The geology, fossils, and human stories of Florissant Fossil Beds National Monument are part of a common geologic heritage. The layers of rock beneath this valley contain one of the richest fossil deposits in the world. They hold clues of unexpected environments and life that existed here during a time called the late Eocene.


11.3: Fossils - Geosciences

All articles published by MDPI are made immediately available worldwide under an open access license. No special permission is required to reuse all or part of the article published by MDPI, including figures and tables. For articles published under an open access Creative Common CC BY license, any part of the article may be reused without permission provided that the original article is clearly cited.

Feature Papers represent the most advanced research with significant potential for high impact in the field. Feature Papers are submitted upon individual invitation or recommendation by the scientific editors and undergo peer review prior to publication.

The Feature Paper can be either an original research article, a substantial novel research study that often involves several techniques or approaches, or a comprehensive review paper with concise and precise updates on the latest progress in the field that systematically reviews the most exciting advances in scientific literature. This type of paper provides an outlook on future directions of research or possible applications.

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to authors, or important in this field. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.


11.3: Fossils - Geosciences

All articles published by MDPI are made immediately available worldwide under an open access license. No special permission is required to reuse all or part of the article published by MDPI, including figures and tables. For articles published under an open access Creative Common CC BY license, any part of the article may be reused without permission provided that the original article is clearly cited.

Feature Papers represent the most advanced research with significant potential for high impact in the field. Feature Papers are submitted upon individual invitation or recommendation by the scientific editors and undergo peer review prior to publication.

The Feature Paper can be either an original research article, a substantial novel research study that often involves several techniques or approaches, or a comprehensive review paper with concise and precise updates on the latest progress in the field that systematically reviews the most exciting advances in scientific literature. This type of paper provides an outlook on future directions of research or possible applications.

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to authors, or important in this field. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.


20.3 Fossil Fuels

There are numerous types of fossil fuels, but all of them involve the storage of organic matter in sediments or sedimentary rocks. Fossil fuels are rich in carbon and almost all of that carbon ultimately originates from CO2 taken out of the atmosphere during photosynthesis. That process, driven by solar energy, involves reduction (the opposite of oxidation) of the carbon, resulting in it being combined with hydrogen instead of oxygen. The resulting organic matter is made up of complex and varied carbohydrate molecules.

Most organic matter is oxidized back to CO2 relatively quickly (within weeks or years in most cases), but any of it that gets isolated from the oxygen of the atmosphere (for example, deep in the ocean or in a stagnant bog) may last long enough to be buried by sediments and, if so, may be preserved for tens to hundreds of millions of years. Under natural conditions, that means it will be stored until those rocks are eventually exposed at the surface and weathered.

In this section, we’ll discuss the origins and extraction of the important fossils fuels, including coal, oil, and gas. Coal, the first fossil fuel to be widely used, forms mostly on land in swampy areas adjacent to rivers and deltas in areas with humid tropical to temperate climates. The vigorous growth of vegetation leads to an abundance of organic matter that accumulates within stagnant water, and thus does not decay and oxidize. This situation, where the dead organic matter is submerged in oxygen-poor water, must be maintained for centuries to millennia in order for enough material to accumulate to form a thick layer (Figure 20.18a). At some point, the swamp deposit is covered with more sediment — typically because a river changes its course or sea level rises (Figure 20.18b). As more sediments are added, the organic matter starts to become compressed and heated. Low-grade lignite coal forms at depths between a few 100 m and 1,500 m and temperatures up to about 50°C (Figure 20.18c). At between 1,000 m to 5,000 m depth and temperatures up to 150°C m, bituminous coal forms (Figure 20.18d). At depths beyond 5,000 m and temperatures over 150°C, anthracite coal forms.

Figure 20.18 Formation of coal: (a) accumulation of organic matter within a swampy area (b) the organic matter is covered and compressed by deposition of a new layer of clastic sediments (c) with greater burial, lignite coal forms and (d) at even greater depths, bituminous and eventually anthracite coal form. [SE]

There are significant coal deposits in many parts of Canada, including the Maritimes, Ontario, Saskatchewan, Alberta, and British Columbia. In Alberta and Saskatchewan, much of the coal is used for electricity generation. Coal from the Highvale Mine (Figure 20.19), Canada’s largest, is used to feed the Sundance and Keephills power stations west of Edmonton. Almost all of the coal mined in British Columbia is exported for use in manufacturing steel.

Figure 20.19 The Highvale Mine (background) and the Sundance (right) and Keephills (left) generating stations on the southern shore of Wabamun Lake, Alberta [SE]

While almost all coal forms on land from terrestrial vegetation, most oil and gas is derived primarily from marine micro-organisms that accumulate within sea-floor sediments. In areas where marine productivity is high, dead organic matter is delivered to the sea floor fast enough that some of it escapes oxidation. This material accumulates in the muddy sediments, which become buried to significant depth beneath other sediments.

As the depth of burial increases, so does the temperature — due to the geothermal gradient — and gradually the organic matter within the sediments is converted to hydrocarbons (Figure 20.20). The first stage is the biological production (involving anaerobic bacteria) of methane. Most of this escapes back to the surface, but some is trapped in methane hydrates near the sea floor. At depths beyond about 2 km, and at temperatures ranging from 60° to 120°C, the organic matter is converted by chemical processes to oil. This depth and temperature range is known as the oil window. Beyond 120°C most of the organic matter is chemically converted to methane.

Figure 20.20 The depth and temperature limits for biogenic gas, oil, and thermogenic gas [SE]

The organic matter-bearing rock within which the formation of gas and oil takes place is known to petroleum geologists as the source rock. Both liquid oil and gaseous methane are lighter than water, so as liquids and gases form, they tend to move slowly toward the surface, out of the source rock and into reservoir rocks. Reservoir rocks are typically relatively permeable because that allows migration of the fluids from the source rocks, and also facilitates recovery of the oil or gas. In some cases, the liquids and gases make it all the way to the surface, where they are oxidized, and the carbon is returned to the atmosphere. But in other cases, they are contained by overlying impermeable rocks (e.g., mudrock) in situations where anticlines, faults, stratigraphy changes, and reefs or salt domes create traps (Figure 20.21).

Figure 20.21 Migration of oil and gas from source rocks into traps in reservoir rocks [SE]

The liquids and gases that are trapped within reservoirs become separated into layers based on their density, with gas rising to the top, oil below it, and water underneath the oil. The proportions of oil and gas depend primarily on the temperature in the source rocks. Some petroleum fields, such as many of those in Alberta, are dominated by oil, while others, notably those in northeastern B.C., are dominated by gas.

Figure 20.22 Seismic section through the East Breaks Field in the Gulf of Mexico. The dashed red line marks the approximate boundary between deformed rocks and younger undeformed rocks. The wiggly arrows are interpreted migration paths. The total thickness of this section is approximately 5 km. [SE after http://wiki.aapg.org/File:Sedimentary-basin-analysis_fig4-55.png]

In general, petroleum fields are not visible from the surface, and their discovery involves the search for structures in the subsurface that have the potential to form traps. Seismic surveys are the most commonly used tool for early-stage petroleum exploration, as they can reveal important information about the stratigraphy and structural geology of subsurface sedimentary rocks. An example from the Gulf of Mexico south of Texas is shown in Figure 20.22. In this area, a thick evaporite deposit (“salt”) has formed domes because salt is lighter than other sediments and tends to rise slowly toward the surface this has created traps. The sequence of deformed rocks is capped with a layer of undeformed rock.

Exercise 20.4 Interpreting a Seismic Profile

The cross-section shown here is from a ship-borne seismic survey in the Bering Sea off the west coast of Alaska. As a petroleum geologist, it’s your job to pick two separate locations to drill for oil or gas. Which locations would you choose?

[from USGS at: http://walrus.wr.usgs.gov/infobank/programs/html/definition/seis.html]

The type of oil and gas reservoirs illustrated in Figures 20.21 and 20.22 are described as conventional reserves. Some unconventional types of oil and gas include oil sands, shale gas, and coal-bed methane.

Oil sands are important because the reserves in Alberta are so large (the largest single reserve of oil in the world), but they are very controversial from an environmental and social perspective. They are “unconventional” because the oil is exposed near the surface and is highly viscous because of microbial changes that have taken place at the surface. The hydrocarbons that form this reserve originated in deeply buried Paleozoic rocks adjacent to the Rocky Mountains and migrated up and toward the east (Figure 20.23).

The oil sands are controversial primarily because of the environmental cost of their extraction. Since the oil is so viscous, it requires heat to make it sufficiently liquid to process. This energy comes from gas approximately 25 m3 of gas is used to produce 0.16 m3 (one barrel) of oil. (That’s not quite as bad as it sounds, as the energy equivalent of the required gas is about 20% of the energy embodied in the produced oil.) The other environmental cost of oil sands production is the devastation of vast areas of land where strip-mining is taking place and tailings ponds are constructed, and the unavoidable release of contaminants into the groundwater and rivers of the region.

At present, most oil recovery from oil sands is achieved by mining the sand and processing it on site. Exploitation of oil sand that is not exposed at the surface depends on in situ processes, an example being the injection of steam into the oil-sand layer to reduce the viscosity of the oil so that it can be pumped to the surface.

Figure 20.23 Schematic cross-section of northern Alberta showing the source rocks and location of the Athabasca Oil Sands [SE]

Shale gas is gas that is trapped within rock that is too impermeable for the gas to escape under normal conditions, and it can only be extracted by fracturing the reservoir rock using water and chemicals under extremely high pressure. This procedure is known as hydraulic fracturing or “fracking.” Fracking is controversial because of the volume of water used, and because, in some jurisdictions, the fracking companies are not required to disclose the nature of the chemicals used. Although fracking is typically done at significant depths, there is always the risk that overlying water-supply aquifers could be contaminated (Figure 20.24). Fracking also induces low-level seismicity.

During the process that converts organic matter to coal, some methane is produced, which is stored within the pores of the coal. When coal is mined, methane is released into the mine where it can become a serious explosion hazard. Modern coal-mining machines have methane detectors on them and actually stop operating if the methane levels are dangerous. It is possible to extract the methane from coal beds without mining the coal gas recovered this way is known as coal-bed methane.

Figure 20.24 Depiction of the process of directional drilling and fracking to recover gas from impermeable rocks. The light blue arrows represent the potential for release of fracking chemicals to aquifers. [by SE, after https://en.wikipedia.org/wiki/Hydraulic_fracturing#/media/File:HydroFrac2.svg]


Earthquake Magnitude

Before we look more closely at magnitude we need to review what we know about body waves, and look at surface waves. Body waves are of two types, P-waves, or primary or compression waves (like the compression of the coils of a spring), and S-waves, or secondary or shear waves (like the flick of a rope). An example of P and S seismic wave records is shown in Figure 11.13. The critical parameters for the measurement of Richter magnitude are labelled, including the time interval between the arrival of the P- and S-waves — which is used to determine the distance from the earthquake to the seismic station, and the amplitude of the S waves — which is used to estimate the magnitude of the earthquake.

Figure 11.13 P-waves and S-waves from a small (M4) earthquake that took place near Vancouver Island in 1997. [SE]

When body waves (P or S) reach Earth’s surface, some of their energy is transformed into surface waves, of which there are two main types, as illustrated in Figure 11.14. Rayleigh waves are characterized by vertical motion of the ground surface, like waves on water, while Love waves are characterized by horizontal motion. Both Rayleigh and Love waves are about 10% slower than S-waves (so they arrive later at a seismic station). Surface waves typically have greater amplitudes than body waves, and they do more damage.

Figure 11.14 Depiction of seismic surface waves [SE after: https://en.wikipedia.org/wiki/Rayleigh_wave#/media/File:Rayleigh_wave.jpg and https://en.wikipedia.org/wiki/Love_wave#/media/File:Love_wave.jpg]

Other important terms for describing earthquakes are hypocentre (or focus) and epicentre. The hypocentre is the actual location of an individual earthquake shock at depth in the ground, and the epicentre is the point on the land surface directly above the hypocentre (Figure 11.15).

Figure 11.15 Epicentre and hypocentre [SE]

A number of methods for estimating magnitude are listed in Table 11.1. Local magnitude (ML) was widely used until late in the 20th century, but moment magnitude (MW) is now more commonly used because it gives more accurate estimates (especially with larger earthquakes) and can be applied to earthquakes at any distance from a seismometer. Surface-wave magnitudes can also be applied to measure distant large earthquakes.

Because of the increasing size of cities in earthquake-prone areas (e.g., China, Japan, California) and the increasing sophistication of infrastructure, it is becoming important to have very rapid warnings and magnitude estimates of earthquakes that have already happened. This can be achieved by using P-wave data to determine magnitude because P-waves arrive first at seismic stations, in many cases several seconds ahead of the more damaging S-waves and surface waves. Operators of electrical grids, pipelines, trains, and other infrastructure can use the information to automatically shut down systems so that damage and casualties can be limited.

Table 11.1 A summary of some of the different methods for estimating earthquake magnitude. [SE]
Type M Range Dist. Range Comments
Local or Richter (ML) 2 to 6 0‑400 km The original magnitude relationship defined in 1935 by Richter and Gutenberg. It is based on the maximum amplitude of S-waves recorded on a Wood‑Anderson torsion seismograph. ML values can be calculated using data from modern instruments. L stands for local because it only applies to earthquakes relatively close to the seismic station.
Moment (MW) > 3.5 All Based on the seismic moment of the earthquake, which is equal to the average amount of displacement on the fault times the fault area that slipped. It can also be estimated from seismic data if the seismometer is tuned to detect long-period body waves.
Surface wave (MS) 5 to 8 20 to 180° A magnitude for distant earthquakes based on the amplitude of surface waves measured at a period near 20 s.
P-wave 2 to 8 Local Based on the amplitude of P-waves. This technique is being increasingly used to provide very rapid magnitude estimates so that early warnings can be sent to utility and transportation operators to shut down equipment before the larger (but slower) S-waves and surface waves arrive.

Exercise 11.2 Moment Magnitude Estimates from Earthquake Parameters

A moment magnitude calculation tool is available at: http://solr.bccampus.ca:8001/bcc/items/24da5970-c4f3-4ab9-98ed-089a7caca242/1/. You can use it to estimate the moment magnitude based on the approximate length, width, and displacement values provided in the following table:

Length (km) Width (km) Displacement (m) Comments MW?
60 15 4 The 1946 Vancouver Island earthquake
0.4 0.2 .5 The small Vancouver Island earthquake shown in Figure 11.13
20 8 4 The 2001 Nisqually earthquake described in Exercise 11.3
1,100 120 10 The 2004 Indian Ocean earthquake
30 11 4 The 2010 Haiti earthquake

The largest recorded earthquake had a magnitude of 9.5. Could there be a 10? You can answer that question using this tool. See what numbers are needed to make MW = 10. Are they reasonable?

The magnitude scale is logarithmic in fact, the amount of energy released by an earthquake of M4 is 32 times higher than that released by one of M3, and this ratio applies to all intervals in the scale. If we assign an arbitrary energy level of 1 unit to a M1 earthquake the energy for quakes up to M8 will be as shown on the following chart:

Magnitude Energy
1 1
2 32
3 1,024
4 32,768
5 1,048,576
6 33,554,432
7 1,073,741,824
8 34,359,738,368

In any given year, when there is a large earthquake on Earth (M8 or M9), the amount of energy released by that one event will likely exceed the energy released by all smaller earthquake events combined.


Where to Look for Fossils

Quarries are excellent places to find fossils because so much rock is exposed. Old abandoned quarries are best because the rocks have been weathered and the fossils are easier to see and collect.

If you plan to collect in a quarry or any other private property, be sure to get permission to enter it. In that way, someone will know where you are in case of accident. In active quarries, there is danger from falling rock during blasting. If the operator of the quarry doesn't know you are there, he cannot warn you when he is going to set off a blast.

Some of the best collecting sites in Illinois are the cliffs and bluffs along our major rivers, the Mississippi, Illinois, Ohio, and Wabash Rivers and their tributaries. At these places, whole fossils are often weathered out and may be picked up easily. Most of Illinois' major rivers have banks of windblown glacial dust, or loess (pronounced "luss"). Shells of air-breathing snails that lived during the Ice Age are common in the loess.

Well-known collecting sites for plant fossils are coal strip mines of Illinois. Perhaps the most famous is the Mazon Creek area near Braidwood in northeastern Illinois, which has supplied beautifully preserved impressions of ferns, tree leaves, and a few insects to museums throughout the world.

This map of the Mazon Creek will help you locate the area of interest. Many strip mines yield fine brachiopods, snails, clams, and cephalopods.

Highway cuts through bedrock commonly expose beds containing fossils, but be careful along road cuts, especially if there is heavy traffic.

Ice Age fossils, such as mammoth and mastodon teeth and tusks, have been found mostly in gravel pits but also in foundation excavations and ditches in all parts of the state.

Actually, you can find fossils almost anywhere, in the gravel or crushed stone of your driveway or in stone walls and foundations. You may see fossils in many places where you cannot collect them, such as counter tops in restaurants, utility marble in public buildings, in stone sidewalks in several of our older cities, or in riprap along the shores of Lake Michigan and our major rivers.


11.3: Fossils - Geosciences

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Feature Papers represent the most advanced research with significant potential for high impact in the field. Feature Papers are submitted upon individual invitation or recommendation by the scientific editors and undergo peer review prior to publication.

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