composite volcano
A volcano that forms when runny lava escapes through a fissure and flows a long way.
cinder cone
A small volcano built primarily of proclastic material ejected from a single vent. (Mount Shasta, California)
magma
A body of molten rock found at depth, including any dissolved gases and crystals.
Lava
Magma that reaches the Earth's surface.
Pyroclastic
The volcanic rock, ejected during an eruption, including ash, bombs, and blocks.
Shield Volcano
A broad, gently sloping volcano built from fluid basaltic lavas.
Silica
A white or colorless crystalline compound, (SiO2) occurring abundantly in quartz, sand, flint, agate and many other minerals.
Active Volcano
Volcanoes that are erupting or have erupted recently.
Ash
Grayish-white to black powdery residue left when something is burned. Volcanic ash consists of pieces of rock and glass.
Viscosity
A measure of a fluid's resistance to flow.
Caldera
A large depression typically caused by collapse or ejection of the summit area of a volcano.
Pluton
An intrusive igneous structure that results from the cooling and hardening of magma beneath the surface of Earth.
Sill
A tabular igneous body formed when magma is injected along sedimentary bedding surfaces.
Laccolith
A massive igneous body intruded between preexisting strata.
Dike
A tabular shaped intrusive igneous feature that occurs when magma is injected into fractures in the surrounding rock, cutting across preexisting rock layers.
Batholith
A large mass of igneous rock that formed when magma intruded at depth, became crystallized, and subsequently was exposed by erosion; Batholiths have a surface expose greater that 100 square kilometers. (Sierra Navada Batholith)