Rocks and the Rock CycleRocks and the Rock CycleChapter 6Chapter 6

The Rock CycleThe Rock Cycle

What types of rocks were the first What types of rocks were the first type on the Earth?type on the Earth?

IGNEOUS

Bowen’s Reaction SeriesBowen’s Reaction SeriesCanadian Canadian

Geologist, Norman L. Geologist, Norman L. Bowen, recognized Bowen, recognized that certain minerals that certain minerals tend to crystallize tend to crystallize first. As they first. As they crystallize, they crystallize, they remove specific remove specific elements, changing elements, changing the composition of the composition of magma as it cools.magma as it cools.

Partial Melting vs. Fractional Partial Melting vs. Fractional Crystallization Crystallization

Classification of Igneous Classification of Igneous RocksRocks

Intrusive Igneous Intrusive Igneous RocksRocks Slow cooling below Slow cooling below

surfacesurface Visible crystalsVisible crystals

Extrusive Igneous Extrusive Igneous RocksRocks Fast cooling at Fast cooling at

surfacesurface No crystals or very No crystals or very

very small crystalsvery small crystals

Textures of Igneous RocksTextures of Igneous Rocks

Coarse-grained (Granite) Porphyritic

(Rhyolite)

Fine-grained (Rhyolite)

Vesicular (pumice)

Glassy (obsidian)

Composition of Igneous Composition of Igneous RocksRocks

MAFIC FELSIC

Types of LavaTypes of Lava

MaficMafic FelsicFelsic

ColorColor Dark Dark Light Light

CompositionComposition Magnesium/Magnesium/ironiron

Silica, Silica, AluminumAluminum

OriginOrigin Ocean crustOcean crust Cont. crustCont. crust

TempTemp HotHot CoolCool

ViscosityViscosity ThinThin ThickThick

Eruption Eruption TypeType

QuietQuiet ViolentViolent

ExampleExample HawaiiHawaii Mt. St. Mt. St. HelensHelens

Intrusive Igneous Rock Intrusive Igneous Rock FeaturesFeatures

Batholith – large Batholith – large mass (100 mass (100 square km) of square km) of igneous rockigneous rock

Stock – smaller Stock – smaller version of a version of a batholithbatholith

Oregon Batholith after surrounding rock has been eroded away

Laccolith – Laccolith – magma pushes magma pushes overlying upward overlying upward into an archinto an arch

Bear Butte, Black Hills, South Dakota

Sill – magma Sill – magma flows between flows between layers of rock - layers of rock - horizontalhorizontal

Dike – igneous Dike – igneous formation that formation that cuts across rock cuts across rock layers - verticallayers - vertical

A five-mile-long volcanic wall, a dike, radiating from Shiprock in distance

Formation of Sedimentary Formation of Sedimentary RocksRocks

Compaction

Cementation

Chemical Sedimentary Chemical Sedimentary RocksRocks

Evaporites precipitating from the hyper saline brine water in one of the playa lake, Thar desert

Halite (Rock Salt)

Gypsum Rock

Organic Sedimentary RockOrganic Sedimentary Rock

Limestone with Fossils

Chalk

Coal

Clastic Sedimentary RockClastic Sedimentary Rock

Conglomerate (Round) Breccia (Angular)

Sandstone (Sand-sized grains) Shale (Clay-sized

particles)

Sedimentary Rock FeaturesSedimentary Rock Features

Stratification in the Grand Canyon

Cross-beds

Mud Ripples

Formation of Metamorphic Formation of Metamorphic RockRock

Contact Metamorphism

Formation of Metamorphic Formation of Metamorphic RockRock

Regional Metamorphism

Types of Metamorphic RockTypes of Metamorphic RockFOLIATED ROCK

Slate: metamorphic shale

Gneiss: metamorphic granite

Types of Metamorphic RockTypes of Metamorphic Rock

NONFOLIATED ROCK

Quartzite: metamorphic quartz sandstone

Marble: metamorphic limestone