Igneous Rocks and Volcanoes Vocab

Rock Cycle

model that illustrates the origin of the 3 basic types of rocks & the interrelatedness of Earth’s materials and processes

Igneous Rock

rock formed from the cooling and hardening (recrystallization) of molten (melted) minerals

Sedimentary Rock

rock formed from weathered products of pre-existing rocks that have been transported, deposited, compacted, & cemented

Metamorphic Rock

rock formed from the alteration of pre-existing rock under the influence of heat and pressure

Intrusive

igneous rock that formed below the Earth’s surface & has larger crystals

Extrusive

igneous rocks that form on the Earth’s surface & has smaller crystals

Phaneritic

igneous texture composed of large crystals that are visible

Aphanitic

igneous texture composed of small crystals not visible

Porphyritic

igneous texture composed of large and small crystals

Glassy

igneous texture that cooled too quickly to have mineral crystals/grains

Intrusion

igneous emplacement of molten rock in pre-existing rock

Magma

molten material beneath or within the Earth's crust; from which igneous rock is formed

Lava

magma that reaches the Earth’s surface

Volcano

opening where magma erupts onto Earth’s surface

Geyser

a hot spring in which water intermittently boils, sending a tall column of water and steam into the air

Hot Spot

a concentration of heat in the mantle capable of producing magma, which rises to the Earth’s surface

Shield Volcano

type of volcano with broad, gently sloping sides

Stratovolcano

large, steep volcano built up from alternating layer of lava and ash (also known as a composite volcano)

Cinder Cone Volcano

a smaller volcano built from cinders and lava bombs

Diverging

boundary where plates spread apart (sea-floor spreading and rifting)

Subduction

a boundary in which one edge of one crustal plate is forced below the edge of another; can form deep ocean trenches

Mafic

type of lava flow that is less viscous/thin, fast moving, not explosive

Felsic

type of lava flow that is viscous/thick, slow moving, explosive

Pyroclastic

mixture of superheated rock and ash

Viscosity

a measure of a fluid’s resistance to flow, thickness of a liquid