180 likes | 398 Views
Rocks. Earth’s crust is made of rock. Rocks are mixtures of minerals and sometimes other materials. When studying a rock sample , geologists observe the rock’s: Color Texture Chemical composition. Most rocks are made up of grains , particles of minerals , or other rocks.
E N D
Rocks • Earth’s crust is made of rock. • Rocks are mixtures of minerals and sometimes other materials.
When studying a rock sample, geologists observe the rock’s: • Color • Texture • Chemical composition
Most rocks are made up of grains, particles of minerals, or other rocks. • Texture is the look that results from: • Size • Shape • Pattern of rock’s grains
Coarse-grained-- large/easy to see. • Fine-grained – small, even microscopic.
Some rocks have NO grain, because they cooled too quickly when they formed.
There are 3 groups of rocks: • Igneous • Metamorphic • Sedimentary
Igneous Rocks Formed from the cooling of molten (melted) rock. Examples: pumice, granite, basalt
Sedimentary Rocks Formed when particles of other rocks, plants, or animals are cemented together. Examples: Sandstone, breccia, siltstone
Metamorphic Rocks Formed when existing rock is changed by heat, pressure, or chemical reactions. Examples: gneiss, schist, phyllite