PLATE TECTONICS

•TEKS 8.9B relate plate tectonics to the formation of crustal features;

•TEKS 6.10C identify the major tectonic plates

•TEKS 6.10D describe how plate tectonics causes major geological events such as ocean basins, earthquakes, volcanic eruptions, and mountain building

Plate tectonics describes the means by which the ocean and continental crust are able to move and the results of that motion.

What is Plate Tectonics?

Key plates: • Eurasian • African • Indo-Australian

The crust of Earth is divided into

plates.

•Pacific •Nazca •North American •South American

The plates are rigid and in constant motion relative

to one another.

What Causes the Tectonic Plates to

Move?

Intense heat from the core of the Earth causes

convection cells to form in the asthenosphere.

The Earth’s continental and oceanic plates sit on the hot asthenosphere. While the rock in the asthenosphere is solid, it is less rigid than the plates, and therefore moves.

While scientists do not fully understand the forces that move the plates, it is believed that the moving material in the asthenosphere drags the plates along.

What Are the

Results of Tectonic

Plate Motion?

Each plate moves as a distinct unit. The borders between plates are called plate boundaries.

There are three different kinds of motion that occurs

between the tectonic plates. •Divergent Plate Boundary

•Transform Plate Boundary

Even though the motion of the plates is very slow; about 10-

40 mm/year (this is about how fast your fingernails grow), the motion causes major geologic events and

surface features.

I can out run the tectonic

plates!

TRANSFORM Motion: plates grind past one another

Geologic Event:

earthquakes

Surface Feature: faults

San Andreas Fault

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DIVERGENT Motion: plates move away from one another

Geologic Event:

•new crust is formed

•shallow earthquakes

Surface Feature:

•Rifts •Rift valleys

•Volcanic islands

•mid-ocean ridge

rift valley Mid-Atlantic

Ridge

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CONVERGENT Motion: plates move toward one another

Geologic Event:

•crust material is destroyed

•earthquakes •volcanic eruptions

•mountain building

CONVERGENT Surface Features:

•volcanoes • Island arcs •Volcanic arcs •Trenches •Mountain

ranges

MOUNT SAINT HELENS

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THE HIMALAYAN MOUNTAINS

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