Exam 23: Geologic Timereading the Rock Record

Earth's early life forms were marine organisms. Life moved to the land during the

To date the age of Earth, we look for rocks with a high percentage of

The rather simple idea that, unless disturbed, younger sedimentary layers overlie older layers, is referred to as the principle of

An assumption that Earth processes occurring today have always occurred is called

The ultimate truth of any radiometric date depends on the

Uplift of the Rocky Mountains was a result of

The formation of the supercontinent of Pangaea

Deposition of sediment with each new layer younger than the layer below illustrates the principle of

The banded iron formations began to form when

Describe the conditions of Earth during the Precambrian.

Dinosaurs were abundant during the

The fundamental time unit representing a major change in life forms is the

Life forms in the Precambrian include

To help determine the age of rock layers over a large area we can use the principle of

The five principles used to determine the relative ages of rock include original

The emergence of terrestrial life-for example, land plants, came about during the

The most noteworthy highlight of the Cenozoic era was the

What types of rocks are representative of the principle of original horizontality? Why?

In any sequence of sedimentary rock layers that have not been subjected to stress, you would expect to find

What types of changes occurred in land-dwelling animals during the Mesozoic?