Exam 24: Geologic Time

An important radiometric dating process is the decay of potassium-40 to ______________-40.

The K-T event occurred about ______________ million years ago.

The hollow depression left when a shell or bone is dissolved completely out of a rock is called a(n) ______________.

Petrified wood is a common type of ______________ fossil.

The Petrified National Forest is found in the state of

The Devonian is a(n)

Sedimentary layer A is found above sedimentary layer B, and the two are separated by a horizontal layer of ash, C. Therefore, the order from oldest to youngest is

Wood from an ancient stump has a ratio of carbon-14 to carbon-12 that is one-eighth that of new wood. About how old is the stump? (Carbon-14's half-life is 5730 years.)

The Paleozoic is a(n)

The first 87% of geologic time is often called

Which of the following radionuclides has the shortest half-life?

The Paleozoic era began about how many million years ago?

The Jurassic is a(n)

The process of matching up rock layers in different localities by such means as index fossils is called

Trace fossils are

Eras are divided first into

The Great Dying occurred at the end of the ______________ era.

The K-T impact is thought to have occurred at what site?

Which occurrence is associated with the demise of the dinosaurs?

Geologists think that Earth is how old?