EARTHQUAKES VOLCANOES - Monadnock Regional High School

[Pages:32]EARTHQUAKES &

VOLCANOES

EFFECTS OF PLATE TECTONICS

When plates move, they bump into each other

Depending on the type of plate boundary, different deformations result

Two special events/formations happen as well:

Earthquakes Volcanoes

EARTHQUAKES

Earthquake: shaking of the ground that results from the movement of rock beneath Earth's surface

Stress on rocks from pushing/pulling changes its shape/volume of the rock

Types of Stress:

Shearing ? causes rocks to slip Tension ? stretches rock Compression ? pushes rocks together

FAULTS

Fault: a break in Earth's crust where slabs of crust slip past each other.

Rocks on both sides of a fault can move up or down or sideways

Usually occur along plate boundaries, where the forces of plate motion compress, pull or shear the crust so much that it breaks.

TYPES OF FAULTS

Strike-Slip Faults: where rocks on either side of the fault slip past each other sideways with little up or down motion

Occurs at transform plate boundaries Ex: San Andreas Fault, California

Normal Faults: a fault at an angle so one block of rock lies above the fault and the other block of rock lies below the fault, caused by tension

Occurs where plates diverge Hanging wall ? half that lies above Footwall ? half that lies below

TYPES OF FAULTS

Reverse Faults: have the same structure as a normal fault, but the blocks move in the opposite direction (toward each other)

Produced by compression forces Ex: produced part of the Appalachian Mountains in the

eastern US

FRICTION ALONG FAULTS

Friction is the force that opposes motion between surfaces

When friction along a fault is low, the rocks pass easily without sticking

When friction along a fault is high, the rocks lock together and do not move.

Energy continues to build until it's strong enough to overcome friction.

When they jerk free, you get an earthquake

The strength of the quake depends on the amount of energy built up (how much friction there was)

MEASURING EARTHQUAKES

Two things we need to know when earthquakes happen:

Where they're located How "big" they were

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