Environmental Geology135 - Lecture Exam 1: Rocks

Define minerals

An inorganic, crystalline structure that has an elemental formula

Define rocks

Composed of one or more minerals

Define and describe a fine igneous rock texture

Cools quickly, smaller crystals

Define and describe a coarse igneous rock texture

Cools slowly, larger crystals

Describe the iron (Fe) and magnesium (Mg), silica, and crystallization/melting point temperatures of mafic rocks

Iron: highest Magnesium: highest Silica: lowest Crystallization/Melting point: highest

Describe the iron (Fe) and magnesium (Mg), silica, and crystallization/melting point temperatures of felsic rocks

Iron: lowest Magnesium: lowest Silica: highest Crystallization/Melting point temp: lowest

Describe the iron (Fe) and magnesium (Mg), silica, and crystallization/melting point temperatures of intermediate rocks

Iron: middle Magnesium: middle Silica: middle Crystallization/Melting point: middle

How are minerals and rocks different

Rocks are composed of minerals and minerals are not composed of rocks

How do igneous rocks form?

Take any rock, heat and melt it which creates magma, remove from heat source to the surface

Explain how intrusive (plutonic) igneous rocks are formed

magma never reaches the surface to cool down.

Explain how extrusive (volcanic) igneous rocks are formed

magma reaches surface (lava) to cool down