Unit 5 Earth's Landforms: Volcanoes

explosivity

rate of explosion; is related to viscosity, silica content, amount of dissolved gasses

magma

molten mixture of rock-forming substances, gases, and water from the mantle

viscosity

a measure of a fluid's thickness or resistance to flow

volatiles

the gaseous component of magma; materials that will vaporize (form a gas) at surface pressures

tephra

bits of rock or solidified lava dropped from the air during an explosive volcanic eruption; ranges in size from volcanic ash to volcanic bombs and blocks

lava

magma that has erupted onto Earth's surface and cooled

magma chamber

a location where magma collects inside Earth

volcano

an erupting vent through which molten rock and other materials reach Earth's surface, or a mountain built from the products of an eruption

silica

a mineral found in magma formed from the elements oxygen and silicon; another name for the chemical compound silicon dioxide; most abundant mineral in the Earth's crust

vent

an opening exposed on Earth's surface where volcanic material is emitted

mantle plume

heated lower mantle rock that rises toward the lithosphere and forms a hot spot on the overlying lithospheric plate

pyroclastic flow

a dense, destructive mass of very hot ash, lava fragments, and gases ejected explosively from a volcano and typically flowing downslope at great speed