Rocks ROCKS Chapter 3

Rocks Naturally occurring solid material made of one or more minerals Grouped into 3 main types, based on the way it was formed

IGNEOUS ROCKS #1

Formed from magma that cools and hardens “Fire Formed” IGNEOUS ROCKS Formed from magma that cools and hardens “Fire Formed”

IGNEOUS ROCKS: 2 types Intrusive rocks: Cools slowly, large crystals formed deep within Earth Cools slowly, large crystals Coarse grained Extrusive rocks: formed from lava at Earth’s surface Cools quickly, small crystals fine grained

IGNEOUS ROCKS: texture Size of crystal grains and chemical composition are used to classify igneous rocks Texture depends on time it takes a rock to harden (cooling rate)

IGNEOUS ROCKS: porphyry (POR-fuh-ree) Igneous rock with a mixture of large and small crystals

Two types of magma Felsic: Light-colored Thick and slow flowing Rich in silica Mafic: Dark-colored Very fluid Rich in iron

Scoria

Igneous Rock Structures Intrusions –underground rock masses Extrusions – surface rock masses

Batholiths INTRUSIONS largest igneous intrusions Form when huge bodies of magma cool underground Cover 1000 km

Batholith

INTRUSIONS Laccoliths Domelike masses formed from magma bulging upward

This laccolith in Red and White Mountain, Colorado, is of Tertiary age. Overlying layers of rock have been eroded.

INTRUSIONS Dike Sheets of igneous rocks that cut across the rock layer

Dike

Dike

INTRUSIONS Sill Sheet of hardened magma that forms between and parallel to layers of rock

Sill

Volcanic neck: EXTRUSIONS The plug of hardened magma left in the vent from which lava flowed

Volcanic neck:

INTRUSIONS Stock Similar to batholiths but less than 100 km

SEDIMENTARY ROCKS #2

75% of Earth’s surface is sedimentary rock! Sedimentary Rocks 75% of Earth’s surface is sedimentary rock!

How Sedimentary Rocks are made: Mud, sand, gravel and shells are sediments that make up rocks Sediments are moved by wind and water Compaction: Pressure placed in sediment layers cause them to change to rocks Cementation: sediments are joined together (cemented) by minerals dissolved in water This process results in the formation of layers called strata.

The major characteristics of all sedimentary rocks is that they form layers!

...We both have layers." Ogres are like sedimentary rocks! "For your information, there's a lot more to ogres than people think... Ogres are like sedimentary rocks! …Sedimentary rocks have layers... Ogres have layers! ...We both have layers."

Sedimentary rocks usually form in water Ripple marks and mud cracks

Fossils often preserved in sedimentary rocks

Sedimentary Rocks: Classified by Composition Texture Grain size

Types: Clastic Organic Chemical

Formed by broken pieces or fragments of rock 1. Clastic Rocks Formed by broken pieces or fragments of rock Classified according to size and shape of fragments

Clastic Rocks Conglomerates: Made of rounded pebbles and other rocks of different sizes and cemented together by clay, mud ,or sand Formed when rivers deposit large pieces of rock Pieces of rock rounded by water before deposited

Conglomerate:

Clastic Rocks Breccia: Similar to conglomerates, but fragments are sharp and angular Not carried far enough by water to round the edges

Breccia:

Clastic Rocks Sandstone: Made of small, sand-sized grains Very common Resistant to wear and decay Used to make buildings

Sandstone:

Formed from small particles of clay Example: shale Clastic Rocks Mudrock: Formed from small particles of clay Example: shale

shale

shale

Formed directly or indirectly from material that used to be living 2. Organic Rock Formed directly or indirectly from material that used to be living

Fossilized Limestone: Organic Rock Fossilized Limestone: Shells from dead animals (containing calcium carbonate) that sink to bottom of ocean floor

Limestone:

Organic Rock Chalk: Composed of animals and calcium carbonate that have been pressed together

Chalk

Organic Rock Coal: Rock formed from plants that lived millions of years ago

3. Chemical Rock Formed by chemical means that do not involve any living organisms Can occur through evaporation or chemical action

Formed directly from ocean water instead of organisms Chemical Rock Limestone: Formed directly from ocean water instead of organisms

Chemical Limestone:

Natural form of common table salt Ex: Halite Chemical Rock Rock salt: Natural form of common table salt Ex: Halite

Chemical Rock Rock gypsum:

METAMORPHIC ROCKS #3

Metamorphic Rocks Metamorphism: Changing of one type of rock in to another due to - Tremendous heat Great pressure Chemical reactions ( a change in composition of minerals)

Metamorphic Rocks Types of Metamorphism: Contact Metamorphism Occurs when rocks are heated by contact with magma or lava Covers a small area Regional Metamorphism Occurs when rocks are buried deep beneath Earth’s surface and changed by increase in temperature and pressure Covers a large area

Types of Metamorphic Rock: Foliated Texture: Mineral crystals arranged in parallel layers or bands (flatten under pressure) Slate  Schist  Gneiss (from clay or shale) (from granite, basalt, or slate) (from granite)

Foliated Texture: slate

Foliated Texture: phyllite:

Foliated Texture: gneiss:

Types of Metamorphic Rock: 2. Unfoliated Texture: No bands of crystals Don’t break in layers

Unfoliated Texture: marble

Unfoliated Texture: quartzite