PLATE TECTONICS

Dr. Sunil Kumar Singh A

Dept. of Geography

G.D. College, Begusarai

CONTINENTAL DRIFT

� Evidence for Continental Drift

� Theory of continental drift is the idea that the continents have moved horizontally to their current locations.

� This theory was developed by Alfred Wegener.

� Wegener believed that all of the continents were � Wegener believed that all of the continents were

connected as one large land

mass which he called as

Pangaea about 200 million

years ago.

Alfred Wegener (1880Alfred Wegener (1880--1930)1930)

THEORY OF PLATE TECTONICS� Plate Tectonics

A. Theory of Plate Tectonics is the idea that the Earth’s crust and upper mantle are broken into sections called plates that move around on the mantle.

B. Composition of the Earth’s plates:

1. Lithosphere – the crust and part of the 1. Lithosphere – the crust and part of the upper mantle

2. Asthenosphere – the plastic-like layer below the lithosphere

PLATE BOUNDARIES

� There are three different plate boundaries:

� Divergent Boundaries

� Convergent Boundaries

� Transform Boundaries

DIVERGENT BOUNDARIES� Divergent Boundaries are the boundaries between

two plates that are diverging, or moving away from

each other.

CONVERGENT BOUNDARIES

� Convergent Boundaries are the boundaries between two plates that are converging, or moving towards each other.

� There are three types of convergent boundaries:

1. An ocean floor plate collides with a less dense continental plate.

2. An ocean floor plate collides with another ocean floor plate.

3. A continental plate collides with another continental plate.

�� OceanicOceanic--ContinentalContinental

OceanicOceanic--OceanicOceanic ��OceanicOceanic--OceanicOceanic ��

�� ContinentalContinental--ContinentalContinental

ANDES MOUNTAINS,

SOUTH AMERICA

AALEUTIANLEUTIAN IISLANDSSLANDS, A, ALASKALASKA

TRANSFORM FAULT BOUNDARIES

� Transform Boundaries are the boundaries between

two plates that are sliding horizontally past one

another.

SAN ANDREAS FAULT, CALIFORNIA

EFFECTS OF PLATE TECTONICS

� Landforms caused by plate tectonics:

a. rift valleys (divergent boundaries)

b. mountain ranges (continental-continental

convergent boundaries)

c. volcanoes (oceanic-continental convergent c. volcanoes (oceanic-continental convergent

boundaries)

d. faults (transform boundaries)

CAUSES OF PLATE TECTONICS

� Convection Current is the driving force of plate

tectonics in which hot, plastic-like material from

the mantle rises to the lithosphere, moves

horizontally, cools, and sinks back to the mantle.

� The convection currents provide enough energy to

move the plates in the lithosphere.

MAJOR PLATES