Geologic History & Earth Layers Flashcards

Flashcards about Geologic History and Earth Layers

What is geologic history?

The history of the Earth from its formation to the present.

How old is the Earth?

4.6 billion years old.

What is an era in geologic terms?

A major division of geologic time.

What are the key characteristics of the Pre-Cambrian Era?

Began 4600 million years ago, ended 570 million years ago; formation of Precambrian shields; first single and multi-celled organisms formed.

What are the major characteristics of the Paleozoic Era?

Began 570 million years ago, ended 245 million years ago; shallow seas in North America, Appalachian Mountains formed; age of amphibians & fish, first insects, large swamps, first plants & animals on land.

What are the key characteristics of the Mesozoic Era?

Began 245 million years ago, ended 66 million years ago; formation of Rocky Mountains begins, Innuitian Mountains formed, shallow seas; age of reptiles and dinosaurs, first flowering plants, first birds & mammals.

What are the major characteristics of the Cenozoic Era?

Began 66 million years ago, has yet to end; Rocky Mountains completed, ice sheets, continents take present shapes; age of the mammals, human beings develop, modern life evolves.

What are the main characteristics of the Earth's crust?

Rocky, outer surface of the earth, 10-70 km thick, made of solid rock, thin under oceans and thick under continents.

What are the key characteristics of the Earth's mantle?

Layer of dense rock about 2900 km thick, made of liquid rock (magma) that moves in convectional currents.

Describe the Earth's outer core.

About 2000 km thick, made of heavy metals, semi-solid rock like jell-o.

What are the characteristics of the Earth's inner core?

About 1400 km thick, thought to be made of solid nickel and iron, hottest part of the earth (3700 C), gravity prevents it from turning to liquid.