Earthquakes, Volcanoes, and Tsunamis
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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