Chapter 3 Rocks

The Rock Cycle Rock – naturally occurring, consolidated mixture of minerals Three types (igneous, sedimentary, metamorphic) Mineral – naturally occurring, inorganic crystalline material with a unique chemical composition

The Rock Cycle The Rock Cycle – interactions among Earth’s water, air, and land can cause rocks to change from one type to another in a continuous process Magma – molten material that forms beneath Earth’s surface Lava – magma that reaches Earth’s surface

The Rock Cycle Igneous rocks form when magma cools and hardens

The Rock Cycle Weathering – process in which rocks are physically and chemically broken down by water, air, and living things Sediments – weathered pieces of Earth materials

The Rock Cycle Sedimentary rocks – sediments are compacted and cemented together

The Rock Cycle Metamorphic rocks - under extreme pressure and temperature sedimentary rock will change into metamorphic rocks

The Rock Cycle

Igneous Rocks Igneous rocks – form when magma or lava cools and hardens Two types: Intrusive – rocks that form when magma cools beneath Earth’s surface As magma cools crystals grow and combine to form rocks such as granite Extrusive – rocks that form when lava cools and hardens As lava rapidly cools at Earth’s surface rocks such as Rhyolite form

Igneous Rocks Classification of Igneous Rocks – texture and composition Coarse-Grained Texture – slow cooling, large crystals Fine-Grained Texture – rapid cooling, small crystals Glassy Texture – cools very rapidly, crystals unable to form Porphyritic Texture – magma cools very slowly, some crystals form quicker than others creating large crystals surrounded by small grains Granitic Composition – extrusive, made of quartz and feldspar, makes up the continental crust Basaltic Composition – intrusive, contains magnesium and iron resulting in dark colors Use page 74 in your text to help identify igneous rock types.

Sedimentary Rocks Sedimentary Rocks – form when sediments become compacted and cemented Arches National Park - Utah

Sedimentary Rocks Formation Weathering, Erosion, and Deposition Weathering – chemical/physical breakdown of rocks Erosion – movement of weathered material by water, wind, ice, or gravity Deposition – when sediments are dropped in a location via erosion Compaction and Cementation Compaction – process that squeezes/compacts sediments Cementation – dissolved minerals are deposited in tiny spaces among sediments Use page 79 in your text to help identify sedimentary rock types.

Sedimentary Rocks Classified into two groups based on formation Clastic – made of weathered bits of rocks Grouped according to sediment size Examples – Sandstone, Siltstone, Shale Chemical – made of dissolved rocks found in/around water, as water evaporates, fine solids are left behind Examples – limestone, rock salt, flint

Sedimentary Rocks Features - unique features are clues to how, when, and where rocks formed Formed by layers of sediments – oldest layers on the bottom Ripple marks – show that the rock formed along a beach or stream bed Fossils – helps us study the climate and environment millions of years ago

Metamorphic Rocks Metamorphic Rocks – form when existing rocks are changed by heat and pressure

Metamorphic Rocks Formation Contact Metamorphism – magma moves into rock Regional Metamorphism – large scale change occurs during mountain building events Agents of Change Heat – provides energy to drive chemical reactions Rocks are baked, creating new minerals and crystals Pressure – causes rocks to compress May cause new minerals to form

Metamorphic Rocks Classification – based on texture Foliated – contact metamorphism, layers/banded appearance Example - Slate Non-foliated – crystals combine to form larger interlocking crystals Example - Marble Use page 84 in your text to help identify sedimentary rock types.