Ask a Scientist FAQ

What is geology? What is paleontology?

Geology is the study of the Earth throughout its history, and includes the study of any processes that happen within the Earth (plate tectonics, volcanism, earthquakes) or upon its surface (climate change, glaciers, ocean currents, the evolution of life). Therefore, paleontology is only a small subset of geology that looks at life (in the form of fossils) as it has evolved through time. To understand the fossils, a paleontologist has to understand the rocks from which the fossils were collected, and to understand the rocks, one must understand the forces that formed them, eroded them, and brought them together. A wet climate erodes (breaks down) rocks much faster than a dry climate, and evidence of the climate fossils lived in is preserved in their shells, much like a tree’s rings. Other disciplines, like chemistry, math, and physics, help geologists to put the entire picture together. Thus, to understand any one aspect of geology, a student must consider its entirety, which makes geology a multidisciplinary science filled with questions perfect for engaging students.

Why is studying paleontology or geology important?

Fossils are not just rocks; they are preserved animals from earlier times in Earth’s history. To understand life on Earth today, we need to learn about the way life has changed since it emerged on Earth. “Visible life,” meaning the first real abundance of animals with hard skeletons (and therefore able to be preserved and seen today) evolved near the Pre-Cambrian/Cambrian boundary around 545 million years ago. Therefore, we have 545 million years of pre-historical animals that have shaped our Earth and the organisms upon it today. This theory, called evolution through natural selection, helps us to understand why some organisms are cold-blooded (like reptiles), and others are warm-blooded (like mammals) based on the habitats to which they have adapted. But more than helping to explain our world today, understanding evolution has created the medical scientific advancements that have saved countless lives. An example of this is seen in the flu vaccine people are inoculated with every year. The flu virus is small and evolves rapidly, so medical scientists must understand this evolution to create new vaccines yearly to combat the evolving virus.

Paleontology is also an important topic of study because it allows other sciences to be more easily grasped. In high school biology, cell biology and genetic mutation are typical curriculum, and this is typically where evolution is explained. Linnean taxonomy (kingdom, phylum, class, order, family, genus, species) is also covered here. If evolution were presented to students prior to high school biology using multi-cellular life that they were already familiar with, like clams and snails, these curricula would be much more easily grasped. Example: Gastropods and clams are related (taxonomy) because they grow in the same way. Looking at a clam, you can see one edge grows the fastest. If you increase the speed of that growth, you can create a spiral-shaped shell, a gastropod. Slight differences in habitat and the way each organism lived, and the natural selection of organisms better suited for their environments, throughout the last 545 million years have created two entirely different organisms! This helps explain why organisms are classified the way they are (Linnean taxonomy), which would otherwise be strict memorization on the part of high school students, as well as how animals can change through time (evolution).

What is a fossil and how does it form?

A fossil is an organism, or trace of an organism (like a footprint or worm tube), that has been preserved in rock. When an organism like a clam dies, its shell slowly gets covered by sediment. Once the sediment becomes thick enough, it begins to compact together and form a rock. The organic material in the shell slowly gets replaced by another mineral, like silica (quartz), calcite, or pyrite (fool’s gold), but keeps valuable information like isotope data for measuring temperature, precipitation, and age in the fossilized shell. Sometimes a shell gets filled with sediment before it gets compacted and the shell dissolves away. However, the sediment inside the shell can harden and preserve an internal mold, or steinkern. The sediment outside of the shell can preserve an external mold, too. These molds are examples of trace fossils.

Some organisms are very fragile, like a crinoid (sea lily). These organisms have an exoskeleton made of plates that are held together by soft tissue (like muscle, tendon, or cartilage). When they die, the soft tissue decays rapidly, and the plates of the crinoid fall apart and can quickly be separated by water energy or another organism scavenging or digging nearby. That is why crinoid crowns are found much less frequently than their stems, which are held together more rigidly. If a fragile organism is preserved (we have starfish that are over 400 million years old), the organism was buried almost instantaneously after death. It is thought that events like turbidites (underwater landslides) instantly kill and preserve many of these types of fragile or soft-bodied organisms.

What is taphonomy and why should we care?

Taphonomy is the study of everything that happens to an organism between when it dies and when it is collected. For instance, after a clam dies, its muscles relax and the two shells separate. This is why we commonly see only one clam shell, and rarely see two still together. Then the shells can quickly be buried in sediment, slowly be buried, or can even be tossed around by a storm before being covered by storm debris. All of these things tell us about the habitat the clam was living in. If it slowly gets buried, it was likely living in very deep water where waves from even the biggest storms would not disturb the bottom of the water column, so the only sediment covering it would be fine grained silt that floated on the currents and eventually settled out in the deep, still water. If it was covered instantly, we can look at the sediment to see what kind of event caused the burial. If it was covered in storm debris, we know that where the clam lived was affected by storms.

In contrast to a clam, a brachiopod uses its muscles to open its shell. Therefore, when it dies, it naturally closes up, so we commonly see the two valves of a brachiopod together. Something would have to happen after death (taphonomically) to separate the valves. And again, from looking at the sediment around it, we can determine the habitat in which the brachiopod lived.

The longer a fossil has been exposed to the surface, the more taphonomically altered it will become. This is why we ask students to record fragmentation. While we cannot accurately measure fossil fragments, areas with high fragmentation are of interest to paleontologists who want to study storms and other taphonomy issues.

Why do we have fossils in Central New York?

Paleogeographic map of the northeastern United States during the Devonian Era.

Today central New York is miles from the Atlantic Ocean, and the organisms living in lakes like Cayuga or Seneca today are fresh-water and cannot tolerate saltwater. However, scientists have reconstructed how New York looked in the Devonian Period (416 to 354 million years ago) and determined that the entire state was covered in a shallow sea, and was located much closer to the equator than it is today. In a shallow, subtropical, marine environment ~380 million years ago, the organisms living in New York looked a lot differently than they do today. Museum of the Earth in Ithaca, NY. Teachers from schools serving diverse and underrepresented student groups are strongly encouraged to apply. The Fossil Finders project will prepare teachers to use fossils to engage study, geology, and scientific inquiry.

Scientists have reconstructed the paleogeography of New York by studying Devonian-aged rock samples throughout the world. For instance, we know that rocks full of salt deposits lie beneath the Devonian rocks in New York. These are older (Silurian aged), and from research of modern day environments, we know that salt deposits form in very shallow seas with a warm climate that allows evaporation. This is just one line of evidence that shows geologists and paleontologists the environment was like here in NY in the past. We also know that coral today can only live in warm, marine waters. Therefore, finding ancestral coral in the Devonian rocks of New York shows that around 380 million years ago this area was covered by a shallow, warm ocean.

Because a lot of things have happened in the 380 million years since the fossils were living in New York, they haven’t been preserved everywhere. Most notably, the last 110,000 years have been riddled with ice ages that have repeatedly sent glaciers south, from Canada, that have scraped the surface of New York and many other northern states. This process has removed countless tons of rock, creating things like the gorges near Ithaca, the Finger Lakes, and the Great Lakes. Glaciers also deposited rock from other areas as they retreated north when climate warmed. Events like these have formed New York’s topography as it is today, and make certain areas perfect for collecting fossils, and others barren.

Why are there fossils in some sedimentary rocks and not in others?

The sedimentary rocks we see today are a reflection of the environment in which they were deposited as unconsolidated sediments millions of years earlier. Some sediments are deposited in marine environments that are conducive to life of marine organisms. Marine invertebrate organisms, like those found in the Fossil Finders Project, need salt water that is continuously supplied with oxygen, nutrients like iron, nitrogen, and phosphate, and is never too salty or too fresh. Sedimentary rocks that lack fossils are reflecting environments that were inhospitable for organisms during the time of their deposition. It is likely, in most cases, that there is some evidence of past organisms in rock that appears to be barren of fossils. Sometimes fossils are less common, or the only things able to preserve are their tracks or burrows (we call them trace fossils) because of different types of preservation and taphonomy processes.

Common Invertebrate Descriptive Terms

  • Benthic: The organism lives on the bottom of the sea floor
  • Pelagic: The organism lives in the water column
  • Sediment-Water Interface: The point in the water column of an ocean where the sea floor meets the bottom of the sea water; can be shallow or deep.

What is a bivalve (clam)?

A bivalve (clam) is a mollusk with two shells that are symmetric to one another. They live either at the sediment water interface, or they dig into the ground beneath the water. The rounded edge where the shells meet is called the commissure, and this is where the organism protrudes from its shell to interact with the outside world.

It propels itself with a ‘foot’ muscle which protrudes from one side of the commissure, and feeds and breathes with siphons that protrude from the other side of the commissure. This is why clams have a sometimes elongate or strange shape. Where they live in the sediment/on the ocean floor shows how much or how little they have to dig, and how long their siphons must be to feed. Therefore, the measurements that are made by scientists must take into account why the organism has a certain shape, and must take consistent measurements to be sure they are measuring the same parts of differently shaped clams.

What is a brachiopod?

A brachiopod is an organism with two shells that are not symmetric to one another, however each half of a shell is symmetric with its other half (like our head, the front and back are not symmetrical, but each side is symmetrical).

They live attached to the seafloor using a pedicle. To feed, they part their shells and allow water to pass through. Inside the shell they have a lophophore that hangs down and filters the water for food internally. Because their individual shells are symmetrical, they attach to the ground with a pedicle that comes out the back, and they do not protrude parts to move or feed, the measurements scientists make are straightforward and easy to take.

What is the difference between a brachiopod and a bivalve in ancient time?

Generally, brachiopods live at the sediment-water interface and are attached to something on the seafloor, and therefore cannot readily move. Clams do not attach to anything and are much more active.

This means some can live on the seafloor and clap their valves together to ‘swim’ short distances, whereas others dig into the ground and hide, shooting only their siphons up to the seafloor to feed. They live and eat in very different ways, so it is important to be able to distinguish a brachiopod from a clam, and to take measurements that reflect the way each organism lives. By looking, a clam will have two shells that are symmetrical to one another, or one shell that looks assymetrical. A brachiopod will have two shells that look very different from one another (one may display a dip or fold in the shell, while the other displays a rise in the shell), but cutting an individual shell in half will display symmetry.

What is a coral?

A coral can be either a colonial organism, meaning made of many individuals living as one, or an individual organism.

Fossil corals do not show the remains of actual organism body, but they do show the chambers in which all of the organisms once lived and secreted. Colonial corals generally resemble large sheets of calcite with multiple body chambers. The individual body chambers are lined internally with vertical walls that help support the organisms in life.

What is a bryozoan?

A bryozoan is a colonial organism with very small individual organisms (zooids) living together and excreting an exoskeleton, which is what we see in the fossil record.

The individual holes in the exoskeleton are the places in which the individual zooids lived, attached to the exoskeleton. In some bryozoans, zooids have special functions, with some feeding, some producing currents, and some in charge of reproduction. Because the colony cannot function well without the individual zooids, a bryozoan is considered a colonial organism.

What is the difference between a coral and a bryozoan?

Although they are different, corals and bryozoans had similar life habits, and as a result their morphology (or body structure) is sometimes similar.

In general, bryozoan body chambers (zooecium) are very small in size and a magnifying glass is needed to see them well. Coral body chambers are much larger and have a greater size distribution, anywhere from half of the size of a dime to the size of a fifty-cent piece. Coral body chambers are also lined with vertical walls that help to support the organisms’ soft parts.