Take a look at this geologic
map of Montana. The different colors represent the different types of rocks that are currently exposed, both by type of rock and by time period.
Imagine that you are a paleontologist in search of Tyrannosaurus rex. Where would you start looking?
CLICK on the part of Montana that has the right age and type of rocks for T. rex fossils.
Hint: T. rex lived during the Cretaceous period, a part of the Mesozoic era.
Ooops!
It is true that these are sedimentary rocks, but they are from the Paleozoic, which is a time before dinosaurs had evolved. Try again....
Correct!
There are a lot of sedimentary rocks from the Mesozoic in Montana. These
rocks are the right age and type to preserve fossils of T. Rex. Let’s try searching for another type of fossil.
The very earliest fossils of animals actually occur in rocks more than
540 million years old! This is referred to as the Precambrian Time. Take a
look at the map again. Would Montana be a good place to find fossils of the
Precambrian?
Well, it is true that there are Precambrian rocks in Montana, so the age is right. But look carefully at the type of rock. Try Again.
Correct!
It is true that there are Precambrian rocks in Montana, but they are all metamorphic and so the chances of finding fossils is pretty low.
Ooops!
It is true that these are sedimentary rocks, but they are from the Cenozoic. T. Rex was already extinct. Try again....
Ooops!
This part of Montana has mostly metamorphic rocks from the Precambrian, a time long before the first land animals evolved, and besides, fossils are seldom found in metamorphic rocks. Try again....
Ooops!
Well, these rocks are the right age, but they are igneous. Remember igneous rocks, formed from cooled, molten material, do not contain fossils. Try again....
Ooops!
These rocks are from the Cenozoic. T. Rex was already extinct. They are also the wrong type of rock. Remember igneous rocks, formed from cooled, molten materal, do not contain
any fossils. Try again....
