Earthquakes and Plate Tectonics

Plates … what are they?:

Inner core composed of

SOLID iron & nickel

The plates of a divergent boundary

move away from one another

Plates … what are they?

Outer Core is composed of

LIQUID iron & nickel

Plates … what are they?

Mantle is solid, but PLASTIC layer made up of

silicon, oxygen, magnesium & iron

Plates … what are they?

Boundary between the crust and

mantle is the Moho Discontinuity

Plates … what are they?

Earth’s outermost layer is

the Crust

Plates … what are they?

Plates

pieces of the Earth’s Lithosphere

Plates … what are they?

Lithosphere

Crust + Rigid Upper Mantle

Plates … what are they?

Lithosphere moves on top of the

Asthenosphere

Plates … what are they?

Asthenosphere = the solid, plastic layer of the mantle beneath the lithosphere

Made of mantle rock that flows very slowly, which allows tectonic plates to move on top of it.

Two different kinds of crust

Continental crust

25 to 70 km thick, lower density, granitic composition

Two different kinds of crust

Oceanic Crust

7 to 10 km thick, higher density, basaltic composition

What causes plates to move?

Convection currents in the mantle

What causes plates to move?

Convection currents in the mantle

The warmer material rises to the surface at the ridges

The cooler, denser material sinks at the trenches

Divergent boundary

Is also called a Spreading Ridge

Examples of a divergent boundary are

Mid-Atlantic Ridge

East Pacific Rise

Features of a divergent boundary are?

Ridge

Rift valley

Convergent boundary – Subduction Zone:

Two plates move toward each other,

and one plate sinks under the other

Convergent boundary – Subduction Zone:

Ocean crust sinks under continental crust because

it’s DENSER

Convergent boundary – Subduction Zone Examples:

Peru-Chile Trench

Mariana Trench

Convergent boundary – Subduction Zone Features:

Trench

Volcanoes

Convergent boundary – Collision Zone: Two plates move towards

one another

Convergent boundary – Collision Zone:

Continental-Continental collision –

mountains are formed

Convergent boundary – Collision Zone Examples:

Himalayan Mountains

Alps

Convergent boundary – Collision Zone Features:

Mountains

Transform Boundary

Two plates slide past one another

Transform Boundary Examples:

San Andreas Fault

East Anatolian Fault

Transform Boundary Features

Faults

Applied stress cause rocks to bend and stretch,

undergoing elastic or plastic deformation.

Once their elastic limit is passed. The rocks remain bent and

may break and move along surfaces called faults.

A movement or trembling of the ground that is caused by a

sudden release of energy when rocks along a fault move is an EARTHQUAKE

Force & Faults:

Tension - pulls apart:

Normal Fault

Force & Faults:

Compression - pushes together

Reverse Fault

Force & Faults

Shear - slides sideways

Strike - slip fault

Epicenter - The point on the surface,

directly above an earthquake’s focus

Focus - The point in the Earth’s interior where

the energy release occurs from the earthquake

Three stations are needed to determine the

epicenter location

Types of Earthquake/Seismic waves:

P-Waves (PRIMARY Waves):

Waves that move through the Earth by

causing particles to rocks to move back and forth in the same direction

P-Waves (PRIMARY Waves)

move the fastest

move through liquid, solid & gas

Types of Earthquake/Seismic waves

S-Wave (SECONDARY Waves):

Waves that move through the Earth by

causing particles in rocks to move at right angles to the direction of the wave

Types of Earthquake/Seismic waves:

S-Wave (SECONDARY Waves):

* Arrive second

* Moves only through solids

Types of Earthquake/Seismic waves:

Surface Waves:

Love Waves: rock moves side-to-side and

perpendicular to the direction in which waves are traveling

Types of Earthquake/Seismic waves

Surface Waves:

Rayleigh Waves:

ground moves with an elliptical, rolling motion

Rayleigh Waves cause

the most destruction

Seismogram:

a tracing of earthquake motion recorded by a seismograph

Seismograph: instrument used to record

P-waves

S-waves

L-waves

Richter Scale

Measures the ground motion from an earthquake to find the Earthquake’s strength

Mercalli Scale: Intensity expressed through Roman numerals

provides a description of the effects of earthquake intensity

A noted fault is the

San Andreas Fault

Earthquakes in the US & World within

the last 7 days

Tsunami: Ocean waves generated by

earthquakes

Tsunami: Can travel as fast as

450 mph

Tsunami: States most at risk are

Hawaii and Alaska