Vocabulary List

Fossil Metamorphism Sediment
Intrusive Rocks Mineral  Sedimentary Rock
Lava Rock Volcanic Glass

FOSSIL
The remains or traces of plants or animals which lived long ago, now usually preserved in sediments or sedimentary rocks – may include preserved shells or bones, imprints, carbon residues or preserved tracks.

INTRUSIVE (IGNEOUS) ROCKS
Magma (molten rock) which crystallizes beneath the Earth’s surface; most common type is granite.

LAVA (EXTRUSIVE IGNEOUS ROCK)
Molten rock which flows out of a volcano onto the earth's surface.

METAMORPHISM
The changes in the types and textures of minerals which are caused by the exposure of rocks to great heat and squeezing beneath the Earth’s surface – sedimentary rocks in particular are changed by this process into metamorphic rocks.

MINERAL
A natural inorganic chemical substance always made up of the same kinds of chemicals put together the same way.  Minerals are the building blocks of rocks.
(Substances like coal and volcanic glass are not minerals, as they do not always contain the same chemicals arranged the same way, and coal is composed of organic materials.)

ROCK
A natural solid substance made up of one or more types of minerals.  Rocks can be identified by the kinds of minerals present (composition) and their size and shape (texture).

SEDIMENT
Loose particles produced by the weathering and erosion of older rocks, or by chemical deposition from water or by living organisms.  Sediments are deposited by water, wind and glaciers.

SEDIMENTARY ROCK
Deposits of sediment which have been compressed and cemented together into hard layers.

VOLCANIC GLASS (OBSIDIAN)
Lava which cools so quickly that its chemicals do not have time to form minerals, so instead become natural glass.  Volcanic ash is a dust-sized form of obsidian.