A Trip Through Geologic Time

Originally, the geologic time scale placed Earth’s rocks in order by

The law of superposition helps geologists determine the absolute age of a rock layer

A fossil formed when minerals replace all or part of an organism is called a

The extinction of the dinosaurs gave warm-blooded animals called___ a chance to become abundant

During what era did the Permian Mass Extinction occur?

Geologists divide Earth’s long history into smaller units that make up the geologic time scale

What are the two characteristics that make a good index fossil?

When was most of the coal in the world produced?

A(n)_ is a gap in the geologic record where some rock layers have been lost because of erosion.

What are fossils?

What was the cause of the Permian mass extinction?

The order of the rock layers can be altered by

Jawless fish were Earth’s first ____________________, or animals with backbones

Earth’s earliest atmosphere lacked which gas that is necessary for life to exist today?

A(n)__ fossil forms when dissolved minerals replace the remains and then harden to form rock

Which best describes the climates of Europe and North America during the Quaternary Period?

The relative age of a rock is

Footprints and trails are examples of trace fossils.

The climate in the center of Pangaea was probably a(n)

Sometimes layers of rock are overturned so that the younger rock layers may be on the bottom

During what era did the dinosaurs live?

How old is the Earth?

During what era did complex life evolve during the Cambrian explosion?

Geologists use radioactive dating to

During what period did the dinosaurs go extinct? (not counting birds)

What has the study of fossils allowed scientists to do?

Fossils usually occur in metamorphic rock

The time it takes for half of the atoms in a sample of a radioactiveelement to decay is the

Potassium-40 is useful for dating very old rocks because it has a(n) _____ of1.3 billion years.

During the Paleozoic, the first organisms to live partly on land were