Review for Volcano’ Test
Volcano: a mountain that forms when molten rock is forced to the Earth’s surface
Magma: molten rock below the surface of the earth
Composition of magma determines whether a volcanic eruption is non-explosive or
explosive.
Different Types of Volcanoes
A. Shield Volcanoes: Built out of layers of lava from repeated non-explosive eruptions
B. Cinder Cone Volcanoes: Small volcanic cones made entirely of pyroclastic material
from moderately explosive eruptions
C. Composite Volcanoes:
(Referred to as Stratovolcanoes)
Formed by explosive eruptions of pyroclastic material followed by quieter
outpourings of lava forming alternating layers
EX: Japan’s Mount Fuji
The Formation of Magma
Magma rises to surface because it is less dense than the surrounding rock
Solid rock becomes magma when pressure is released, temps rise above melting point, or
when its composition changes
Explosive Eruptions: clouds of hot debris and gases shoot out from the volcano at supersonic
speeds
Divergent Boundaries: As tectonic plates move apart, a deep crack, or rift, forms between
the plates.
Lithospheric plates: Large pieces of the earth that are always moving
Hot Spots : Places on the earth’s surface that are directly above columns of rising magma of
mantle plumes.
High Water Content: likely to cause the volcano to erupt explosively
Lava Types
Blocky- very thick; oozes from volcano
Pahoehoe- flows slowly; glassy surface with wrinkles
Aa- pours out quickly; jagged surface
Pillow- forms underwater
Pyroclastic Material:
Produced when magma explodes from a volcano and solidifies in the air
Pyroclastic Types
Volcanic Blocks- largest type; consist of solid rock
Volcanic Bombs- large blobs of magma that harden in the air
Lapilli- pebble-like bits of magma that harden in the air
Volcanic Ash- can stay suspended in the atmosphere for years; can fall to earth as a fine
powder or get mixes with water from glaciers or rain.
Average global surface temperatures can drop if the ash and gases spread around the globe
blocking out sunlight.
REVIEW OF EARTHQUAKES
Waves: one or more of a series of movements passing along a surface or through a substance.
Body Waves: Travel through the earth
Earthquake: the shaking and vibration of the earth caused by large and sudden releases of
energy
Epicenter: The point on the earth’s surface that is directly above the focus