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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
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