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Episode 1: How Do You Know Where To Dig?


Welcome to the New Jersey State Museum’s Ask the Experts Video Learning Library. 
My name is Jason Schein and I’m a paleontologist here at the State Museum, and co-leader of the Bighorn Basin Dinosaur Project. In this inaugural season of the Video Learning Library, we’re going to focus on paleontology, or the study of ancient and extinct plants and animals  

As any paleontologist can tell you, there are a lot of misunderstandings out there about our science. This video series is going to dig into some of the most commonly asked questions we get, so that folks have a better idea of what it is that we do, and how we do it. So, let’s get started.

One of the most common questions paleontologists get is “How do you know where to dig?”  After answering that question many times over the years, I’ve realized that people really mean two different things when they ask it. They either mean “On the entire surface of the earth, how do you know where to find dinosaurs?” or they mean “Once you get to a site, how do you know exactly where to start digging to find the dinosaurs?”  Both are good questions, so we’re going to dig right into that first question this time, and save the other question for next time.

So, how do we know where on Earth to start searching?  Couldn’t we just walk outside and start looking for fossils?  We could, but we’d almost never find anything that way.  Instead, we save ourselves a lot of time by doing a little background research, any because good research starts with a few good questions.

First, what kind of animals are we looking for?  Life on Earth has changed dramatically over the last 3 billion years, with different time periods and eras being characterized by different groups of animals. The Mesozoic Era, is known as the Age of Reptiles, because reptiles, including dinosaurs, seemed to dominate the landscapes throughout that Era. After studying the rocks and fossils from this Era, we know that there were other types of plants and animals alive during this time too, and we even have an idea of what the climate was like. So when we’re looking in Mesozoic rocks for dinosaur fossils, we often stumble upon other kinds life from the time!

Now that we know what age of rock to look for, next, we need to know what type of rocks to look for.  There are three basic kinds of rocks: igneous, metamorphic, and sedimentary.  Igneous rocks form when magma or lava cools and turn into stone, so those won’t preserve fossils. Metamorphic rocks usually form deep within the earth under a lot of heat and pressure, so usually no fossils in those either. Sedimentary rocks, though, are formed when small particles of sand, silt, clay, and even the skeletons of microscopic organisms, are deposited, or collect in layers.  Usually that means those particles sink down to the bottom of lakes, rivers and oceans.  When plants or animals get buried within these sediments, their remains may be preserved, or fossilized, over thousands or millions of years.

So, if we want to find dinosaurs, we know that we have to find sedimentary rocks on Earth’s surface that are between 230 and 65 million years old.  Great, let’s get started!  Oh . . . wait, do you happen to know where any Mesozoic sedimentary rocks are? That is a pretty specific set of rocks - how are we going to figure out where they are?  Fortunately, other people have already done that for us.

In fact, geologists have mapped the ages and types of rocks over almost the entire surface of the planet!  All we have to do is look at some geologic maps, like this one, to find those Mesozoic-age sedimentary rocks we’re looking for.  These maps show us an incredible amount of information.  Each one of these colors, and the patterns within each color band, tell us the age of the rock and what type it is.  The maps also show us where faults are, areas where the rocks are folded, and even volcanoes!

Thanks to a little digging, we now know some general areas on Earth’s surface where we could find dinosaurs, but once you get out there, you’ll see that these are still huge areas - sometimes thousands of square miles! Finding a dinosaur skeleton out here - even a big one - is like finding a tiny needle buried in a very big haystack. 

So, how do you know exactly where to dig in the midst of all of that vast terrain? We’ll have to dig into that question. Until then, let’s head out to where the dinosaurs are!  As always, thank you for joining us, and keep digging!