Chapter 3 Prentice-Hall Earth Science 2006 Rocks Chapter 3 Prentice-Hall Earth Science 2006

Rock Cycle Rocks broken down into sediments Magma or lava cools Sediments compacted & cemented Magma forms when rocks melt Rocks changed by heat or pressure

Igneous Rocks Formation Classification – Texture Intrusive: magma cools and hardens Extrusive: lava cools and hardens Examples Granite and rhyolite Classification – Texture Coarse-grained – large crystals Fine-grained – small crystals Glassy – cools rapidly, no crystals Porphyritic – different sizes of crystals

Igneous Rocks Classification – Composition Granitic – light colored silicate minerals Quartz, feldspar Basaltic – dark colored Basalt, gabbro

Sedimentary Rocks Formation Weathering – removal of rock by physical or chemical forces Wind, water, ice, or gravity (rock falls) Compaction – squeezing of sediments that forces most water out of the rock Cementation – dissolved minerals are deposited in the tiny spaces in a rock. Acts like a glue.

Sedimentary Rocks Classification Clastic – rocks made of weathered bits of rocks and minerals Examples: shale, breccia Chemical – Dissolved minerals precipitate from water solutions Limestone, chert, flint

Metamorphic Rocks Formation Agents Contact – hot magma moves into rock Marble Regional – Large-scale deformation resulted from extreme pressure and temperature Agents Heat – provides the energy needed for chemical reactions Magma “bakes” rocks and recrystallize minerals

Metamorphic Rocks Classification Stress (Pressure) – causes the spaces between minerals to close. Increases density Reactions in Solution – Hot solutions causes recrystallization by dissolving original minerals and depositing new ones. Classification Foliated – Pressure from contact metemorphism causes crystals to recrystallize at right angles to the direction of the force. Example: Gneiss

Metamorphic Rocks Nonfoliated – Does not have a banded appearance Composed of one mineral Example: marble

Igneous Granite – Intrusive Rhyolite – Extrusive Pumice – Extrusive (cools quickly) Andesite Obsidian Basalt Gabbro Table 1 on page 74

Sedimentary Shale – Clastic Breccia – Clastic Conglomerate – Cementation Sandstone – Compaction/Cementation Coquina – Chemical/Biochemical Chert Coal Table 2 on page 79

Metamorphic Gneiss – Pressure or stress Marble – nonfoliated Quartzite Anthracite Schist Slate Table 3 on page 84