how many earthquakes occur each year??

14

Upload: amelia

Post on 22-Feb-2016

28 views

Category:

Documents


0 download

DESCRIPTION

How many Earthquakes Occur each year??. More than 1 million !!!. What are Earthquakes?. Vibrations of the earth’s crust caused by a sudden release of energy. What causes EQ’s? . Build up of stress along the boundaries of tectonic plates. Stress. - PowerPoint PPT Presentation

TRANSCRIPT

Page 1: How many Earthquakes Occur each year??
Page 2: How many Earthquakes Occur each year??
Page 3: How many Earthquakes Occur each year??

How many Earthquakes Occur each year??

More than 1 million !!!

Page 4: How many Earthquakes Occur each year??

What are Earthquakes?

Vibrations of the earth’s crust caused by a sudden release of

energy

Page 5: How many Earthquakes Occur each year??

What causes EQ’s?

Build up of stress along the boundaries of tectonic

plates

Page 6: How many Earthquakes Occur each year??

StressStress = the total force acting on

crustal rocks per unit of area

3 Kinds of stress 1. Compression – decrease volume2. Tension – pulls apart3. Shear – twist Example : sponge

Page 7: How many Earthquakes Occur each year??

Strain How rocks respond to stress is

called strain Strain = deformation of a

material expressed in rocks by folding (bending)

or faulting (breaking)

Page 8: How many Earthquakes Occur each year??

Elastic Rebound Theory

Describes the process between stress & strain

Page 9: How many Earthquakes Occur each year??

Elastic Rebound Theory• 2 sides along a fault

are locked by friction • Energy in the form of

stress is stored in rock

• When stress exceeds frictional lock, movement occurs

• Energy is released in form of waves

• Rocks rebound to original shape

Page 10: How many Earthquakes Occur each year??
Page 11: How many Earthquakes Occur each year??

Elastic Rebound Theory Demo:

Page 12: How many Earthquakes Occur each year??

Wood blocks, sandpaper, and rubber bands, can model the slow storage and rapid

release of elastic energy

Page 13: How many Earthquakes Occur each year??

In Class

• Read text p 528 – 530• Define stress & strain

Page 14: How many Earthquakes Occur each year??

ANY QUESTIONS?