Textbook: Dynamic Earth Pages 240 – 245

Edmodo: Folders, Week 34

EARTHQUAKES

Introduction Video ( click to view)

Earthquakes are…: VIDEO* Note in the video they say “Hypocenter”. In the

book, it is called the “Focus”. On the exam, FOCUS will be used.

…ground movements. They happen when blocks of rock (tectonic plates) move suddenly and release energy.

The energy released is known as SEISMIC WAVES.

What is an earthquake?

There are 2 main types of seismic waves. VIDEO here.

P waves: Primary WavesThey are the first waves felt during an earthquakeThey are faster than S wavesThey move objects left to right

S waves: Secondary wavesThey are stronger than P wavesThey move slower so are felt laterThe particles on the Earth move at right angles to the

direction the wave is moving.

Seismic Waves

FocusIn the earth, along a fault, where the earthquake

begins.

EpicenterAbove the focus on the Earth’s surface is the

epicenter.

Seismic waves flow out from the focus in all directions

Earthquakes

They occur near tectonic plate boundaries

As the plates move, pressure builds up near the edges. If there is too much pressure, the plates move suddenly. This is an earthquake.

The plate movements cause FAULTS. Faults are breaks in the Earth’s crust. The plates move along these faults. Convection Currents in the Mantle, move the plates. VIDEO

What causes Earthquakes? Video

Most happen near tectonic plate boundaries.This is where there is the most stress from plate movement.

Where do earthquakes happen?

Normal Fault Click for videoNormal Faults happen at DIVERGENT boundaries

3 Types of Faults

All of the Red lines show a divergent boundary (Mid ocean ridge)

Reverse Fault Click for videoReverse Faults happen at CONVERGENT boundaries

3 Types of Faults

Ex: Mariana Trench.The Mariana plate and Pacific plate are converging. The Pacific plate subducts the Mariana Plate.

Strike Slip Fault Click for videoStrike Slip Faults happen at TRANSFORM boundaries

3 Types of Faults

Ex: San Andreas Fault in California, USA

North American plate colliding withthe Pacific plate.

1. Which Seismic wave moves the fastest?

2. What is the point where an earthquake happens in the Earth called?

3. What is the term given the process which moves tectonic plates?

4. Which type of plate boundary can be found at strike slip faults?

5. At convergent boundaries, name the faults that occur.

Quiz

P or primary waves

It is called the focus.

The process which moves tectonic plates is called Convection.

A Transform boundary

Reverse Faults occur at convergent boundaries.

If you have questions about this topic:

See me before exams (at lunch, break time, after school)

Message me over Edmodo or FacebookRe-watch the videos and read the power

points

Please watch the videos