Transcript Earthquakes, Volcanoes, and Tsunamis

Earthquakes
Earthquakes
Earthquakes
 Plate movements cause large forces
 The rock breaks, and this break can sometimes be tens
of kilometers long
 Faults are fractures in the Earth’s surface
 When 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
Earthquakes
 Lots of the biggest earthquakes are along subduction
zones (where the plate is sliding downwards)
 A transform fault is found at a transform boundary
 If the fault is locked for a long time, and suddenly
slips, a major earthquake happens
 If the fault slips all the time, there are lots of minor
earthquakes
 San Andreas Fault, in California, is a long transform
fault; it is locked around San Francisco and around Los
Angeles
Earthquakes
Volcanoes
Volcanoes
 a 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
Volcanoes
 Volcanoes erupt for different reasons
 How much gas is in the magma will effect its eruption
 As 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
Volcanoes
 Most big volcanoes occur along subduction zones
 Hot 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 Zones
 There are plenty of major earthquakes and volcanoes
 Most of the Pacific Oceans has subduction zones, and
so we see the “Ring of Fire”
Subduction Zone
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 Japan
 immense 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