S6E5. Students will investigate the scientific view of how the earth’s surface is formed. c. Classify rocks by their process of formation. Essential Question: How do scientists classify and identify rocks?

Geologists define rocks as a natural substance composed of solid crystals of different minerals that have been fused together into a solid lump.

Rocks are: A solid made of one or more minerals and other materials.

Classifying Rocks: Rocks are classified by the where and how they were formed. Igneous rocks: formed from the cooling and hardening of molten rock. Sedimentary rocks: formed from sediments being compacted and cemented. Metamorphic rocks: existing rock that is changed by heat & pressure

Classifying Rocks

Identifying Rocks Rocks are further identified by: color texture mineral composition

Texture Texture is the quality of a rock that is based on the sizes, shapes, and positions of the rock’s grains.

Grains Particles of minerals that make up a rock.

Grain Size Some rocks have grains that are large and easy to see: these rocks are coarse grained. Other rocks have grains so small they are microscopic: these are fine grained rocks.

Grain Shape Grains can be: fine sand crystals fragments that can be smooth or jagged

Grain Pattern Grains can lie flat in layers like a stack of pancakes. Some have patterns that look like waves or swirls Some resemble rows of beads. Others will have random patterns.

No Visible Grain: Some rocks resemble pieces of glass. These rocks cooled very quickly so crystals did not have time to grow.

Mineral Composition Composition is the chemical makeup of a rock. Composition can describe either the minerals or other materials in the rock.