EarthquakesPlate movements cause large forcesThe rock breaks, and this break can

sometimes be tens of kilometers longFaults are fractures in the Earth’s surfaceWhen the rocks break, the rocks on either

side of the fracture plane slide past one another, until the forces are relieved

Strong vibrations are produced and these are felt as an earthquake

EarthquakesLots of the biggest earthquakes are along

subduction zones (where the plate is sliding downwards)

A transform fault is found at a transform boundaryIf the fault is locked for a long time, and suddenly

slips, a major earthquake happensIf the fault slips all the time, there are lots of

minor earthquakesSan Andreas Fault, in California, is a long

transform fault; it is locked around San Francisco and around Los Angeles

Volcanoes

Volcanoesa volcano is a place where molten rock, and

also solid volcanic fragments and volcanic gases are erupted as the Earth’s surface

Sometimes rock that is deep in the Earth is melted, to form magma

Magma rises upward because it is less dense than the surrounding rock

It does not always reach the surface before it turns to rock again

If it does reach the surface, it forms a volcano

VolcanoesVolcanoes erupt for different reasonsHow much gas is in the magma will effect its

eruptionAs magma gets close to the surface, the

pressure decreases, and gas bubbles out of the magma

Magma with low gas content does not have violent explosions, unlike that with high gas content

Large, explosive volcanoes are the most dangerous

VolcanoesMost big volcanoes occur along subduction

zonesHot spot volcanoes are caused by a hot spot

in the mantle that will continue to generate magma for a long time

Hot spots don’t move, so a line of volcanoes will form as the plate moves. The way the volcanoes form shows the direction and speed that the plate moved

Eg. Hawaiian Islands are hot spot volcanoes

Subduction ZonesThere are plenty of major earthquakes and

volcanoesMost of the Pacific Oceans has subduction

zones, and so we see the “Ring of Fire”

Tsunami tsunami  is a series of water waves caused by

the displacement of a large volume of a body of water

approximately 195 have been recorded in Japanimmense volumes of water and energy are

involved, so tsunamis can devastate coastal regions.

Casualties can be high because the waves move faster than humans can run.

Earthquakes, volcanic eruptions and other large distubances can cause tsunamis