Plate Tectonics

Chapter 10

Continental Drift

Is the movement of continents to there

present locations.

First suggested by a German

meteorologists Alfred Wegener.

Evidence for continental drift

All the continents seem to fit together

One large landmass “Pangaea.”

Fossil, both animal and plant, similarity on now

separated continents.

Fossils indicate climate change of some

continents.

Glacier evidence show continents have moved

Rock formations on different continents are

similar.

The Seafloor

Mid-ocean ridges are underwater

mountain ranges and valleys.

Depth of the ocean is detected by sound

waves.

Seafloor Spreading

Suggested first by Harry Hess, a Princeton

University Scientist.

Is the movement of magma to the Earth’s

crust and pushes the seafloor outward.

Magma cools and becomes the new

seafloor.

Evidence for Seafloor Spreading

Rocks closest to the mid-ocean ridges are

younger than those farther away.

Earth’s magnetic field has reversed many

times during history. This has caused iron

bearing rocks to form different magnetic

poles.

This causes the ability to use magnetic

time scaling.

Theory of Plate Tectonics

Is the combination of continental drift and seafloor spreading.

States that the Earth’s surface is broken into sections called plates.

Plates and the upper part of the mantle make up the lithosphere of the Earth’s surface.

These plates of the lithosphere “float” on the asthenosphere.

Plate Boundaries

Plates interact with each other.

Plates that move apart from each other are called Divergent Boundaries (seafloor spreading).

Plates that move together are called Convergent Boundaries. Here the more dense plate moves under or subducts the less dense one causing volcanoes or they collide and cause mountain ranges.

Plates that slide past each other are called Transform Boundaries. At this type of boundaries earthquakes can occur.

Causes of Plate Tectonics

Convection Current is the movement of a

medium from heating and cooling.

This current causes the movement of

plates and other surface features.

Features caused by Plate

Tectonics

Mountains, volcanoes, faults, rifts valleys

and slip-strike faults are formed from the

acts of Plate Tectonics.

Plate Tectonics

Is now proved by using lasers and

satellites.

Plates are moving at rates ranging from 1

to 12 cm per year.