Transcript Unit 1.4 Earthquakes

Unit 1.4 Earthquakes
Where do earthquakes Occur?
• Earthquakes can occur near the Earth’s surface or far
below the surface.
• Most earthquakes occur at plate boundaries, but some
happen at faults located in the middle of tectonic plates.
Earthquake Locations Around the World
Vocabulary to Know
• Stress: Force that acts on rock to change its shape or
volume
• Fault: When enough stress builds up and rock breaks
• Tension: Stress force that pulls on Earth’s crust
causing rock to stretch in the middle
• Compression: Stress force that squeezes rock until it
folds or breaks
• Epicenter: The point on the Earth’s Surface above an
earthquake’s starting point
• Focus: The point inside the Earth where the
earthquake begins
What Causes Earthquakes?
• Earthquakes are caused by movement along faults.
• When stress is placed on rocks it deforms, or changes.
• This is called Elastic Deformation
• Rock is stretched and bent until it can no longer take the stress.
• When enough stress builds up in the rock it, it slips and energy is
released.
• The rock then returns to its original shape. This is called Elastic
Rebound. Think of a rubber band, you can only stretch it so far
until it breaks and return to its original shape.
• This energy is felt as an earthquake.
3 Types of Faults Associated with
Earthquakes
PLATE MOTION
FAULT TYPE
Transform : plates move
past each other
Strike –Slip Fault: Fault Blocks
move past each other
Convergent: Plates move
together
Reverse Fault: Fault Blocks move
together
Divergent: Plates Move
Apart
Normal Fault: Fault Blocks Move
Apart
Strike- slip Fault occurs at a Transform Boundary
Reverse Fault Occurs at a Convergent
Boundary