Earthquakes Overview and Types

Study Notes

A fault is a break in the Earth's crust where tectonic plates slide past each other.
Earthquakes occur when stress on a fault causes it to suddenly break, releasing seismic waves that cause ground vibrations.
The focus is the point underground where an earthquake originates.
The epicenter is the point on the Earth's surface directly above the focus.
Seismologists study earthquakes and use seismographs to record seismic waves, producing seismograms.
The Richter scale measures the magnitude of an earthquake, which is a measure of the energy released.
Each increase of one whole number on the Richter scale represents a tenfold increase in energy released.

Thrust Earthquakes occur at convergent boundaries where one plate is forced over another, creating a thrust fault.
Submarine Earthquakes occur at divergent boundaries where plates are forced apart, often on the ocean floor where new floor is created.
Strike-Slip Earthquakes occur at transform faults where plates slip past each other.

A tsunami is a series of giant waves caused by the displacement of water, often triggered by underwater earthquakes.
They can reach speeds of 700 to 800 km/hr and heights of 30 meters or more.
Tsunamis differ from regular waves, which are generated by wind and tides.

A volcano is a mountain formed from magma, which is molten rock found beneath the Earth's surface.
Once magma reaches the surface, it is called lava.
Volcanoes are commonly located near tectonic plate boundaries where plates are either sliding or separating.

Volcanic eruptions occur when the pressure of the magma inside becomes too great and it erupts.
Some volcanoes constantly release magma, preventing pressure buildup and eruptions.
The Ring of Fire is a zone of intense volcanic and earthquake activity that circles the Pacific Ocean.