Chapter 8 Study Guide

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• Earth’s crust is made up of rocks

• Rocks are made up of natural, nonliving solid crystals that are called minerals.

• All minerals are made of crystals that have certain physical properties. Minerals are a repeated crystal pattern.

• Mica is a common mineral that forms rocks.

• Rocks differ from each other.  They are made up of different combinations of minerals.

• Minerals are identified by their physical properties such as color, luster, hardness, streak, and cleavage.

• Mohr’s scale for hardness ranks minerals from 1 to 10.  The greater the Mohr’s ranking the harder the mineral is.  Quartz has a hardness of 7 on the Mohr’s scale.

• Talc is a very soft mineral.

• Metamorphic rocks are formed when rocks are changed by great heat and pressure.

• Igneous rocks are formed when magma or lava cools and gardens.

• Halite is another term for salt.

• Some rocks are more compact, such as obsidian, so they will weigh more.  While porous rocks, such as pumice, are lighter.

• Sedimentary rocks are formed when layers of sediment are weighed down and harden.

• Scientist can tell many things form a fossil.  They can tell what ancient plant or animal life was like, what the animal looked like, what the environment was like, and how the environment has changed since then.

• Fossils are formed in sedimentary rocks; the heat and pressure required to form either metamorphic or igneous rock would destroy a fossil.

• Soil forms when weathering causes rocks to break apart, such as with water and plant roots.  Soil contains small bits of rock, decaying plants and animals, and tiny life forms.