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