Volcanoes. How do Volcanoes form? Volcanoes form when hot material from the mantle rises and leaks...
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Transcript of Volcanoes. How do Volcanoes form? Volcanoes form when hot material from the mantle rises and leaks...
Volcanoes
How do Volcanoes form? Volcanoes form when hot material from the
mantle rises and leaks into the crust. The hot material, called magma, rising from
lower ground, gathers in a reservoir called the magma chamber.
Eventually, but not always, the magma erupts onto the surface and forms lava.
Formation of a Volcano
This is a drawing of magma making it's way up through the crust, causing the volcano to expand
prior to eruption.
Where do Volcanoes form? At Subduction zones Along Hot Spots/plumes The opening in Earth’s surface which allow
material to escape is called a vent.
What is Hot Spot? An area in the middle of a lithospheric plate where
magma rises from the mantle and causes eruptions at the Earth's surface.
If the hot spot forces magma to the surface during an eruption, it may create a volcano.
Continual eruptions could eventually build a whole island on the surface. (Ex. Hawaii)
The hot spot is stationary and the plate moves over it.
Hot spots cont…… Hot spots may cause the formation of
geysers or hot springs, rather than lava based eruptions.
Hot Spot
Types of Volcanic Eruptions Explosive: Short, violent eruptions that
break lava into smaller pieces (cinders and ash)
Effusive: Slow, continual eruptions of lava
Categories for Volcanoes Active
Has erupted in the last 100 years Dormant
Has erupted in the last 1000 years Extinct
Hasn’t erupted in over 1000 years
Types of Volcanoes Composite/StratoVolcanoes Formed by Alternating layers of lava and
ash Typically steep sided and have a high
elevation. Explosive Eruptions Ex. Mount Fuji, Japan
Mount St. Helens, WA
Types of Volcanoes cont…..
Shield Volcanoes Formed by continuous eruption of lava over
long periods of time. Usually very large at the base and not very
steep. Effusive eruptions Ex. Mauna Loa and Kilauea in Hawaii
Example of Shield Volcano
Types of Volcanoes Cindercone Formed from the eruption of lava fragments
called cinders. Usually form quite rapidly and are tall and
steep sided. Not as tall as Strato and not as wide as
Shield Ex. Mount Paricutin in Mexico
Cindercone
Types of Volcanic Hazards Lava: Two categories based on appearance Aa Pahoehoe
Lava--Pahoehoe Lava that has a smooth, ropy surface. Typically slow moving and cooling
Pahoehoe
Volcanic Hazards Aa Lava: Rigid, spiky lava Fast cooling, viscous
Aa lava
Volcanic Hazards Tephra: Material that is ejected from the volcano Size decreases as distance from volcano
increases Ex. Cinders, ash, bomb Damage can include: lightening, respiratory
problems, interference with aircraft, destruction of vegetation, building collapse
Volcanic Hazards Poisonous Gases Gas developed as magma heats water
vapor Typical gases released: Carbon Dioxide,
Sulfur Dioxide, Carbon Monoxide, Hydrochloric Acid
Poisonous in large amounts
Volcanic Hazards Pyroclastic Flow Fluidized masses of rock fragments and
gases that move rapidly in response to gravity
Very fast and cause more death than any other hazard
Pyroclastic flows can incinerate, burn, and asphyxiate people.
Pyroclastic Flow
Pyroclastic Flow
http://www.geo.mtu.edu/volcanoes/hazards/primer/pyro.html
Volcanic Hazards Lahar Form from debris avalanches that contain
water from snow and ice which, when released, mixes with loose debris to form a lahar
Massive flooding Extremely dangerous for people living close
to a volcanic eruption
Lahar