What are ... Archaeologists vs Paleontologists vs Anthropologists

 For the next entry into my What are ...? series, I am looking at something that is often confused, the difference between an Archaeologist and a Paleontologist. This confusing was brought up recently when I was reading the question cards in my daughter's game of Dino Math Tracks:

Within the game, there are cards where the person must solve the math word problem in order to figure out how many spaces they can move. This is the card in question:

Archeologists must ship 24 tons of dinosaur bones to the museum. If each truck can hold 2 tons, how many trucks do they need to ship the bones? Move forward that number of spaces.

This brings up a common mistake in everyday life: mistaking what an archaeologist is versus a paleontologist. 

Archaeologist: According to Webster's Dictionary archaeology is the study of past cultures through their surviving relics. 

This means that an archaeologist studies the remains of civilizations that people leave behind. This can include some things like arrowheads to the pyramids, bowls to clothing, eating utensils to cave dwellings, and everything in between. Archaeologists study the changing human behavior but not the changes in our physical selves. This article puts it perfectly:

... archaeology is the reconstruction of ancient behavior from the things people left behind.

Paleontologists: Paleontology on the other hand is the study of life in past geologic periods, according to Webster's Dictionary.  

This means that paleontologists are focused on the life that once lived and often how it connects to the life that is still around. They can look at the physical remains of the animals and plants to reconstruct what they looked like and how they moved and interacted. They can also look at the behavioral remains left behind like footprints and bite traces to determine how the animals lived. All of this combined will often give paleontologists a fairly good idea of what past environments even looked like. Paleontologists are most often thought of as studying dinosaur bones, but there are many types of life that a paleontologist can study and if there was once something living on this planet that we know about, you can be sure that there was, or is, someone that has studied it. 

The difference here is that paleontologists can study any animal remains, but they don't study the behavioral creations of humans. The question then arises, that is humans are animals, then wouldn't a paleontologist then technically also study humans. Here is where lines start to get blurry and people's definitions may vary but there is a cross specialty that encompasses both worlds, and that is anthropology.

Anthropologists: Anthropology is like the blurry boundary between paleontology and archaeology. Webster's describes anthropology as the science of the origin, early development, and culture of humankind. 

Anthropologists study the human remains to discover how our species has evolved over time, physically, behaviorally, and culturally. Archaeology, on the other hand, is typically seen as a sub-category of anthropology focusing only on the physical items humans created and left behind, while human paleontology (a.k.a. paleoanthropology) could be seen as another name for the study of the human evolution and remains typically seen as one of the sub-disciplines within the overarching body of  anthropology. 

As this website puts it: The goal of anthropology is to better understand the different cultures of human history and to look for solutions in human problems. Anthropologists use social, biological, and physical science to get a better grasp on human cultures.

What are...Groups, Formations, and Members

For the next entry into my What are ...? series, I am looking at what exactly do geologists mean when they use terms like Group, Formation, and Members. Although the term "Formation" is used as the primary formal unit of classification, there are many different terms used to identify different bodies of rocks, and they can get a little confusing if you aren't used to it. Rock units can be broken down or combined together into varying degrees of resolution. How closely are you looking at the rocks and how closely related had they been formed will influence how a geologist groups them together. To help illustrate my point I put together this graphic.

When naming rock units, geologists look at the environments that the beds were formed in, the time period in which they formed, how long it took to form the beds, and how different are each of the units compared to those around them. All of the above provide different resolutions of rock units.

Lithostratigraphic Unit (AKA, rock unit) - A body of rock that consists dominantly of a certain lithologic type or combination of types, or has other unifying lithologic features. It may be igneous, sedimentary, or metamorphic, and it may or may not be consolidated. 

Lithostratigraphic units start at the formation level and can be broken down into smaller units, such as members or beds, or can be combined together into larger units, such as groups or supergroups.

Bed - The smallest lithostratigraphic unit, commonly ranging in thickness from a centimeter to a meter or two and distinguishable from the beds above and below. They are rarely given individual names unless they are distinctive for some reason, such as a dated ash layer. 

Member - A lithostratigraphic unit comprising of some specially developed part of a formation. It may be formally defined and named, informally named, or unnamed. A member does not necessarily need to be mappable. A formation also does not need to be divided up into members, or could even have only parts of it seperated out into members, specifically if it is useful to do so.

Formation - The fundamental lithostratigraphic unit that consists dominantly of a certain lithologic type or combination of types. A formation is a lithologically distinct, mappable body of rocks. Being lithologically distinct means that there must be a notable and identifiable contrast between the units of rocks to justify their division into two different formations. There is no limit to how thick, thin, or widespread a formation needs to be. 

Group - A stratigraphic unit that includes two or more associated formations that are usually contiguous or associated and contain significant features in common. Formations though do not need to aggregated into groups unless there is a useful reason to do so. 

Supergroup - The highest degree of lithologic unit grouping, which consists of an assemblage of related groups, or formations and groups, that have significant lithological features in common. Formations and groups only need to be aggregated into a supergroup if there is a useful reason to do so.

What are....Meteorites, Meteoroids, Meteors, Asteroids, and Comets

I occasionally do a set of blogs called "What are...". Here is the next one in the series.

I was reading a book with my daughter, book 8 of the Magic Tree House series - Midnight on the Moon (her current favorite series of books to read) and I came across this passage that seemed off to me:

The main part I was stuck on was:

"Rocks of all sizes crash into the moon from outer space. These rocks are called meteorites."

From what I could remember, meteorite is a term specifically reserved for rocks that crash into Earth. But did it apply to rocks that crashed into the moon (or other planets for that matter) as well? Looking into it, no. This was incorrect. Meteorites are rocks that specifically have traveled through our atmosphere and crashed into the Earth.

So what would be an object that crashed into the moon?  Turns out that NASA scientists just refer to them as meteoroids, as can be seen in this story - A Meteoroid Hits the Moon.

So what are the differences between a meteor, meteorite, meteoroid, asteroid, and comet?

Meteoroid - These are chunks of rock that are floating in space that are smaller than a kilometer in diameter (Hubblesite.org).

Meteor - This is just the flash of light, a shooting star, that you see in the night sky as a meteoroid falls through the atmosphere and starts to burn up. This is not the physical object that is falling (Hubblesite.org).

Meteorite - A meteorite is a meteoroid that has survived entry through the Earth's atmosphere and has crash landed on the surface of the Earth (Hubblesite.org). This term seems to be exclusive to rocks found on Earth, since terms like "Martian meteorite" or "lunar meteorite" are for meteorites found on Earth that originated from Mars or the moon respectively.

Comet - A comet 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" (Nasa.gov).

Asteroid - "Most asteroids are made of rock, but some are composed of metal, mostly nickel and iron. They range in size from small boulders to objects that are hundreds of miles in diameter. A small portion of the asteroid population may be burned-out comets whose ices have evaporated away and been blown off into space. Almost all asteroids are part of the Main Asteroid Belt, with orbits in the vast region of space between Mars and Jupiter. In space, a large rocky body in orbit about the Sun is referred to as an asteroid or minor planet whereas much smaller particles in orbit about the Sun are referred to as meteoroids" (Nasa.gov).

What are ... Varves?

The next entry in my What are Wednesdays series is to discuss varves (First entry here). I ran into this problem when I was teaching Petrology where the students either A) Didn't know what a varve was, or B) Didn't understand how it formed.

Varves from the Green River Formation used as framing in the Geology building at the University of Utah

Varves, as pictured above, are sedimentary features that alternate in color from light to dark, often in thin bands. Some of the most famous varves are found from the Green River Formation of Wyoming and surrounding regions. The Sutton Geology building here at the University of Utah uses a lot of the Green River Formation both for framing materials but also as wall decorations so it was fairly easy to get a picture of some nice varves.

Varves are formed in end glacial lakes. The lakes has a seasonality, where they freeze every winter and are defrosted every summer. What happens is that during the summer sediment run off from the melting glacial is allowed to settle on the bottom of the lake. This produces the light colors which is rich in quartz sand and other sand and silt grains. You can often find drop stones in this layer as well (like that seen in the lower left corner) where a larger grain gets stuck in ice. The ice chunk floats out into the lake and then melts, dropping the larger grains.

During the winter the lake freezes over. The freezing of the lake limits all sediment from entering the lake so no more large sediment grains are deposited on the lake bottom. What does happen though, is that the freezing of the lake kills much of the biological activity that is occurring in the lake and settles the currents in the lake. The settling of the currents allows for finer grained materials and the organic material to settle to the bottom. These are the darker layers.

So each year of a varve is represented by one couplet of bands: 1 light for summer and 1 dark for winter.

That is all I have to say on varves. If you have any questions feel free to ask and if there are any topics you would like me to present on What are Wednesdays let me know.

What are ... Trace Fossils?

I have been meaning to start a new series where I describe certain attributes in geology, and what I am working on in particular, in a new series called What are Wednesdays. The first entry in this group is called What are ... Trace Fossils? I picked this topic because this is what I am working on and basically it is the easiest for me to write up. This won't be a weekly series but one that comes up from time to time as I find interesting things to write about. If you have anything you would like me to write about please feel free to email me or place it in the comments.

So on to the topic, What are Trace Fossils? Trace fossils are not like your typical fossil. They are basically what an animal creates as it does stuff. Stuff can include walking, burrowing, sitting, eating, living, etc. Whenever an animal interacts with the world around it, it leaves evidence, a trace if you will. These traces are what I study. They are not the actual animal but sometimes are found in association with the animal. The easiest way to visualize this that I can think of is with footprints in the snow (as seen below). Footprints are the most basic type of trace fossil. They illustrate locomotion of an organism, whether it is a human, a rabbit, an insect, or anything in between.

But why study trace fossils? What can they tell us other than an organism was there? Well look at the footprint above. You can tell a lot by the spacing of the prints, the shape of individual prints, and even what information may be missing. The shape tells us what animal possible made it. The spacing and inclination of the prints tell us the speed that it was moving and possibly if there was something wrong, like a limp. If there is more than one set of prints you could tell if they were traveling in groups, or maybe even being hunted. There is a lot of information that can be gleamed even from a simple set of tracks.

Now just looking at the three above pictures you can tell that different organisms made them and possibly even what they were doing when they made them, looking for food, searching for shelter, migrating, snowshoeing, etc.

Now take this information and apply it to the rock record. Rocks record things similar to snow except that it has the potential to remain forever. There are many people who study dinosaur tracks just like we were looking at the tracks in the snow above. I personally study burrows on the bottom of the ocean made by some unknown invertebrate animals. Different types of tracks and trails are made in different environments and knowing what environment that is, it makes it possible to determine the environment of deposition of the rock by just knowing what a certain track looks like. It is actually a very useful tool and one that not only paleontologists use but many geologists for determining different aspects from what the ancient environment was to using them to find oil.

I will probably go into this in more detail at a later date but for some good trace fossil blog posts check out  Life Trace of the Georgia Coast by Tony Martin, an expert ichnologist from Emory University. Any questions please feel free to ask.