Plate Tectonics

PLATE TECTONICS

Ch. 16

LAYERS OF THE EARTH

CRUST Thickness: 5 – 40 km

Composition: Oxygen, Silicon, Aluminum,

Calcium, Iron, Sodium, Potassium, Magnesium

Temperature: Up to 1,600 degrees F

MANTLE Thickness: 2,900 km

Composition: Silicon, Oxygen, Iron, Magnesium

Temperature: 1,600 F to 8,000 F

The uppermost part of the mantle is the lithosphere.

Lithos means “stone”.

The soft layer of the mantle, beneath the lithosphere, is the asthenosphere. Asthenes means “weak”.

OUTER CORE Thickness: 2,250 km

Composition: Iron, Nickel

Temperature: 2,200 F to 11,000 F

INNER CORE Thickness: 1,200 km

Composition: Iron, Nickel

Temperature: 9,032 F to 13,000 F

LAYERS OF THE EARTH

Skin of the peach is the crust

Meat of the peach is the mantle

Pit of the peach is the core

TYPES OF ROCKS Igneous

Sedimentary Metamorphic

IGNEOUS ROCKS Formed from

molten material including volcanic lava, ash, or bombs as well as magma below Earth’s surface.

TYPES OF IGNEOUS ROCKS

GRANITE BASALT

SEDIMENTARY ROCKS Made of layers

that have been pressed or cemented together

Pebbles, sand, silt, or clay are sediments

Shells and bones can also be sediments

TYPES OF SEDIMENTARY ROCKS

SHALE LIMESTONE

COAL

METAMORPHIC ROCKS Rocks that are

changed by intense heat and pressure while inside Earth’s surface

Igneous, sedimentary, and even metamorphic rocks can be changed into different metamorphic rocks.

TYPES OF METAMORPHIC ROCKS

SLATE MARBLE

ROCK CYCLE

The rock cycle is a never-ending process of rocks forming, weathering, and changing into other rocks

ROCK CYCLE

FAULTS OCCUR BECAUSE FORCES INSIDE EARTH CAUSE EARTH’S PLATES TO MOVE, PLACING STRESS ON OR NEAR THE PLATE EDGE.

WHEN ROCKS BREAK, THEY MOVE ALONG FAULTS.

Applied forces cause rocks to undergo elastic deformation.

When elastic limits are passed, rocks break.

•Rocks on one side of a fault can move up, down, or sideways in relation to the rocks around them.

Rocks will bend, compress, stretch, and possibly break.

EARTHQUAKE - VIBRATIONS PRODUCED BY BREAKING ROCK. Rocks break, move along the fault, return to original shapes.

Rock on one side of a fault can move over, under, or past each other along fault lines.

SEISMIC WAVES

Are waves generated by an earthquake; can move the ground forward, backward, up & down, side to side.

Focus - an earthquake’s point of energy release.

A seismic wave’s speed and direction change as the wave moves through different layers with changes in densities.

SEISMOGRAPH - MEASURES SEISMIC WAVES.

Consists of a rotating drum of paper + a pendulum with an attached pen.

Makes a paper record of a seismic event called a seismogram.

Shadow zones do not receive seismic waves because the waves are bent or stopped by materials of different density.

Density Generally increases with depth as pressure increases.

CHANGES IN SEISMIC WAVE SPEED ALLOWED DETECTION OF BOUNDARIES BETWEEN EARTH’S LAYERS.

ALTHOUGH EARTHQUAKES ARE NATURAL EVENTS, THEY KILL MANY PEOPLE AND CAUSE A LOT OF DAMAGE.

Seismologists are scientists who study earthquakes.

•Most earthquakes are of a magnitude too low to be felt by humans - 3.0 to 4.9 on the scale.

DIVERGENT PLATE BOUNDARY

A place where two plates move apart, or diverge

Most occur along the mid-ocean ridge where sea-floor spreading occurs.

MID-OCEAN RIDGE

Mountains that lie mostly hidden under the ocean

Iceland is a part of the mid-ocean ridge that rises above the surface.

MID-OCEAN RIDGE

SEA FLOOR SPREADING

The sea floor spreads apart along both sides of a mid-ocean ridge as new crust is added.

As a result, the ocean floors move like conveyor belts, carrying the continents along with them.

SEA FLOOR SPREADING

RIFT VALLEY

Forms along the divergent boundary, only it forms on land

RIFT VALLEY

CONVERGENT PLATE BOUNDARY

The place where two plates come together, or converge

When two plates collide, the density of the plates determines which one comes out on top.

TRANSFORM BOUNDARY

A place where two plates slip past each other, moving in opposite directions

Earthquakes often occur along these boundaries.

TRANSFORM BOUNDARY

SUBDUCTION

A process in which the ocean floor sinks beneath a deep-ocean trench and back into the mantle.

SUBDUCTION