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Earth Science Chapter 9 - Summary Notes
· A volcano is a mountain that forms when molten rock, called magma, is forced to the Earth’s surface.
· If the magma is high in water content, the volcano is more likely to erupt explosively.
· Explosive eruptions contain rock fragments called pyroclastic material. Generally, volcanoes are not explosive and contain lava instead of pyroclastic material.
· Volcanic ash has tremendous effects. It can block sunlight and lower global temperatures. It can ruin crops and cause loss of livestock. It can dam rivers, resulting in floods.
· Shield volcanoes are not very steep because they are formed from layers of runny, nonexplosive lava eruptions.
· Cinder cone volcanoes are made entirely of pyroclastic material. They are steep but erode away quickly because there is no lava to cement it together.
· Composite volcanoes, aka stratovolcanoes, form by explosive eruptions of pyroclastic material followed by outpourings of lava. This combination forms alternating layers.
· A crater is the pit at the top of the central vent of a volcano.
· Before a volcano forms, magma collects deep in the Earth’s crust where it meets the mantle.
· The temperature is hot enough to melt the mantle rock, but it remains solid because there is tremendous pressure.
· The magma rises to the surface because it is less dense than the surrounding rock, just like how air bubbles rise when water boils. The pressure drops, allowing the magma to become liquid.
The Ring of Fire is the border