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Volcanoes Vocabulary

Terms in this set (18)

Magma
molten rock within the earth
Lava
molten rock that has erupted onto the surface of the earth
Volcano
an opening in earth's crust through which molten rock (lava),
rock fragments (ash), and hot gases erupt
Vent
opening in the surface of the earth, through which gas and
erupted material pass
Ash
particles measuring less than 2 mm across (material that is
thrown into the air during a volcanic eruption)
Hot Spot
unusually hot area where molten rock is forced toward the
crust where it melts partially (hot spots are stationary)
Magma chamber
a pool of magma within the earth
Lava dome
steep-sided, bulbous structure that can form on the volcano
summit when thick, viscous lava emerges from a volcano
Lava flow
lava that is "runny" and does not resist flow, and moves
quickly from the vent
Cinders
pebble-sized pieces of congealed lava and rock fragments
Crater
steep, bowl shaped area (walled depression) around a
volcano's vent
Viscosity
tendency to resist flow
Composite volcano
steep, conical volcanoes formed by the alternating eruption of
viscous lava flows and rock fragments
Shield volcano
broad, gentle slopes form almost entirely from the eruption of
less viscous lava flows
Cinder cone
form from congealed lava and rock fragments (tephra) that
have been ejected from a single vent
Caldera
a large, steep-sided, circular or oval volcanic depression that
forms when magma retreats or erupts from a shallow underground magma chamber
Pillow lava
balloon-like mounds that form when lava erupts under water
or empties into the ocean
Lahar
mudflow that occurs when rain falls through clouds of ash or
when rivers become choked with falling volcanic debris
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