Science Test: Volcanoes

Batholith

Large underground body of intrusive igneous rock

Conduit

Passage connecting the magma chamber to the surface vent

Vent

Opening on a volcano where lava is emitted

Cone

The external shape of a volcano

Pahoehoe

Smooth lava texture with low viscosity

A’a

Rough lava texture with high viscosity

Viscosity

Resistance of a fluid to flow

Pyroclastics

Fragments ejected during a volcanic eruption

Lahar

Mudflow of pyroclastic material and water

Explosive Eruption

Eruption style with trapped gas causing explosions

Effusive Eruption

Continuous eruption with less gas

Cinder Cone

Small, steep-sided volcano made of pyroclastic material

Composite Cone

Large volcano with alternating layers of lava and pyroclastics

Shield Cone

Broad, gently sloping volcano built by effusive eruptions

Caldera

Large volcanic crater formed by the collapse of a volcano

Bowen’s Reaction Series

Sequence of mineral crystallization in cooling magma

Vesicular

Rock texture with gas bubbles

Coarse-grained

Large crystal size in igneous rocks

Felsic

Light-colored igneous rocks rich in silica

Mafic

Dark-colored igneous rocks with less silica

Sill

Intrusive igneous rock parallel to existing rock layers

Dike

Intrusive igneous rock cutting across existing rock layers

Batholith

Large mass of intrusive igneous rock beneath the surface

Volcanic Neck

Solidified magma in a volcano's central conduit

Lacolith

Lens-shaped intrusive igneous rock uplifted between rock layers