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

2. 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

3. 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

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

5. 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.

6. 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

7. 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

8. 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

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

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

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

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