Chapter 3

Terms	Definitions
Rock	a lump or mass of hard consolidated mineral matter
Igneous Rock	a type of rock that forms from the cooling of molten rock at or below the surface
Sedimentary Rock	rocks fromed from sediment derived not only from rock fragments but also from plant and animal remains
Metamorphic Rock	A type of rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions
Rock Cycle	a series of processes on the surface and inside Earth that slowly changes rocks from one kind to another
Magma	a molten mixture of rock-forming substances, gases, and water from the mantle
Lava	rock that in its molten form (as magma) issues from volcanos
Weathering	The breaking down of rocks and other materials on the Earth's surface.
Sediments	Loose materials such as rock fragments, mineral grains, and bits of shell that have been moved by wind, water, ice, or gravity.
Intrusive Igneous Rock	rock formed from the cooling and solidification of magma beneath Earth's surface
Extrusive Igneous Rock	rock that forms from the cooling and solidification of lava at Earth's surface
Porphyritic Texture	An igneous rock texture in which large crystals are scattered on a background of much smaller crystals.
Granitic Composition	group of igneous rocks, light colored silicates, mainly quartz and feldspar
Basaltic Composition	Rocks that contain many dark silicate minerals and plagioclase feldspar
Andesitic Composition	..., the composition of igneous rocks lying between felsic and mafic.
Ultramafic	..., igneous rock composed mainly of iron and magnesium-rich minerals
Erosion	..., condition in which the earth's surface is worn away by the action of water and wind
Deposition	..., the natural process of laying down a deposit of something
Compaction	..., The process by which sediments are pressed together under their own weight.
Cementation	..., The process by which dissolved minerals crystalize and glue particles of sediment together into one mass.
Clastic Sedimentary Rock	..., Sedimentary rock that forms when fragments of preexisting rocks are compacted or cemented together.
Chemical Sedimentary Rock	..., sedimentary rock that forms when minerals precipitate from a solution or settle from a suspension.
Metamorphism	..., change in the structure of rock by natural agencies such as pressure or heat of introduction of new chemical substances
Contact Metamorphism	..., a change in the texture, structure, or chemical composition of a rock due to contact with magma.
Regional Metamorphism	..., a change in the texture, structure, or chemical composition of a rock due to changes in temperature and pressure over a large area, generally as a result of tectonic forces
Hydrothermal	..., referring to hot water, such as that produced in the hydrothermal volcanic vents in the sea floor
Solution	..., a homogeneous mixture of two or more substances
Foliated Metamorphic Rock	..., a kind of metamorphic rock in which heat and pressure arrange the minerals in the rock into layers
Nonfoliated Metamorphic Rock	..., metamorphic rock that does not exhibit a banded or layered appearance