How Do We Know When Dinosaurs Lived? Part 3: Combining Dating Techniques To the

Question

How Do We Know When Dinosaurs Lived? Part 3: Combining Dating Techniques To the right is a cross section through sedimentary and volcanic rock layers. Sedimentary rock layer B contains a dinosaur bone. Which two of the absolute age dating methods would you use to determine the age of volcanic rock layers A and C? How could you determine the age of the dinosaur bone? If volcanic rock A is determined to be 90 Ma, and volcanic rock C is determined to be 80 Ma, what is the age of the dinosaur bone? Two students are debating the age of the dinosaur bone. Student 1: The bone is between 80 and 90 million years old. You can't be more specific because you can't determine how fast the layers were deposited. Student 2: I think the dinosaur lived 85 million years ago because the bone is exactly in the middle of the two volcanic layers. With which student do you agree? Why?

Explanation / Answer

1. a ) volcanic material in tuff is well suited for radiometric dating which uses known decay rates for specific unstable isotopes to determine the age of rock that contains that isotope feldspar found in the tuff layers contain an unstable isotope of potassium that can be used for this dating method. use a potassium - argon dating method , over time the unstable potassium isotope from the rocks decay to stable isotope of argon.

b) carbon dating used to find age of dinosaur from the bone .

c )the age of dinosaur between 90 and 80 mya

d ) i agree with student 1 .we canot determine how fast the layers were deposited

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