Chapter 7 Earth's Rocks

Terms	Definitions
Mineral	A natural, solid substance that has a definite chemical composition and physical structure.
Igneous rock	Rock that forms when melted rock cools and hardens.
lava	Magma that is exposed at Earth's Surface
sedimentary rock	Rock that forms when layers of sediment settle and are cemented together
magma	Melted rock within Earth
metamorphic rock	Rock that forms when igneous, sedimentary, or metamorphic rock is changed by pressure, high temperature, very hot water, or a combination of these factors
metamorphism	The process by which metamorphic rock forms.
rock cycle	processes that change rock from one type to another type
bedrock	The bottom layer of soil, made mostly of solid rock
topsoil	The top layer of soil, made in part from broken pieces of lower layers of rock
Cave Crystals	Minerals grow as crystals. If there is enough space they can grow to be as large as 3ft. in diameter and about 50 ft. long.
Rock layers	The Grand Canyons dramatic drop provides a cutaway view of this.
Carved by Water	...Over thousand of years, erosion of the rock by the Potomas River has caused the Great Falls to move 9 miles upstream.
Ancient Secrets	In the 1400's the Inca people of the Andes Mountains used terraces to grow 20 varieties of corn and more than 240 varieties of potato. The terraces prevented rain from eroding what little good soil there was in the high mountains.
What effect do high temperature and pressure have on igneous rock?	They change igneous rock to metamorphic rock.
What characteristic of soil might be most important to farmers?	the amount of water it can retain
What best explains the glassy look of obsidian?	It cooled very quickly
A way that layers of sedimentary rock bind together?	by pressure
a cause of regional metamorphism	mountain building