Presentation on theme: "Volcanoes. How do Volcanoes form? Volcanoes form when hot material from the mantle rises and leaks into the crust.rises The hot material, called magma,"— Presentation transcript:
How do Volcanoes form? Volcanoes form when hot material from the mantle rises and leaks into the crust.rises The hot material, called magma, rising from lower ground, gathers in a reservoir called the magma chamber.magma chamber Eventually, but not always, the magma erupts onto the surface and forms lava. eruptslava
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.
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
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
Volcanic Hazards Aa Lava: Rigid, spiky lava Fast cooling, viscous
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.
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