What is a Rock Naturallyoccurring mixtures of minerals

What is a Rock? • Naturally-occurring mixtures of minerals, mineraloids, glass or organic matter.

What is a Rock? • Rocks are divided into 3 groups based on how they were formed: • IGNEOUS • SEDIMENTARY • METAMORPHIC

What is the difference between a rock and a mineral? • Rocks are made up of ONE or MORE minerals.

Once a rock is formed, does it stay the same rock forever? • NO!

• Rocks are continually changed by many processes, such as weathering, erosion, compaction, cementation, melting, and cooling • Rocks can change to and from the three types

What is the process through which rocks change? • The Rock Cycle—earth materials change back and forth among the different types of rocks

• No set path a rock takes to become another kind of rock

IGNEOUS Igneous Weathering, Erosion, Compaction, Cementation Heat and Pressure Melting, Solidification Heat and Pressure METAMORPHIC Metamorphic Sedimentary SEDIMENTARY Weathering, Erosion, Compaction, Cementation

How are rocks redistributed? • The core, mantle, & crust are one giant rock recycling machine

***Watch the Rock Cycle by Brainpop 1. What do igneous rocks form from? 2. What kind of rock is sandstone? 3. What are metamorphic rocks formed by?

• “Ignis” = Latin for “fire” • Formed from the cooling of either magma or lava • The most abundant type of rock • Classified according to their origin and composition

ORIGIN— Where rocks are formed INTRUSIVE Igneous • Below ground = from magma • Usually have LARGE crystal grains (they cooled slowly)

Intrusive Igneous Textures: Porphyritic texture - large crystals imbedded in a smaller matrix Phenocryst. Conspicuosly large crystal embedded in smaller crystals

Intrusive Igneous Texture Phaneritic texture- igneous rock texture crystals are roughly the same size - large enough to be seen with the unaided eye Examples: Granite Diorite Gabbro

Origin Extrusive Igneous • Above ground = from lava • Usually have SMALL or NO visible crystals (they cooled too quickly)

Extrusive Igneous. Texture Aphanatic - igneous rock texture in which the crystals are too small to be seen with the unaided eye Basalt Rhyolite Pumice Obsidian Andesite

Pyroclastic Igneous rocks- shot from a volcano (still igneous) Tuff - frothy volcanic ash formed from huge sudden volcanic events Volcanic breccia - volcanic rocks composed of particles larger than ash Bombs - large solid rocks ejected by volcanoes

COMPOSITION— What kind of substances the rocks are made of

Basaltic Igneous Rocks —made from lava/magma that is low in silica, rich in iron and magnesium. Rocks are dark-colored.

Granitic Igneous Rocks—made from magma/lava high in silica and oxygen. Rocks are light-colored.

Andesitic Igneous Rocks— have a composition between basaltic and granitic.

Crystallization - process where ions arrange themselves into orderly patterns as magma cools

• Formed from sediments (rock fragments, mineral grains, animal & plant remains) that are pressed or cemented together or when sediments precipitate out of a solution. • These sediments are moved by wind, water, ice or gravity.

What turns sediments into solid rock? • Water or wind breaks down and deposits sediment (erosion & deposition)

• The heavy sediments press down on the layers beneath (compaction)

• Dissolved minerals flow between the particles and cement them together (cementation)

3 Types of Sedimentary Rocks: 1. Clastic (also called Detrial)—made of broken pieces of other rocks Examples: Shale- Mud and silt Sandstone- Sand Conglomerate- gravel Shale Sandstone Conglomerate

3 Types of Sedimentary Rocks: Organic—remains of plants and animals are deposited in thick layers • Examples • Fossil rich limestone-is made from the shells of ocean animals often imprinted with fossils • Chalk- made from shells • Coquina- Limestone that has larger pieces of shells COQUINA FOSSILIFEROUS LIMESTONE CHALK

3 Types of Sedimentary Rocks: • Chemical—minerals dissolved in lakes, seas, or underground water • EXAMPLESRock salt - Halite Limestone (not all) Rock Gypsum Travertine (chemical limestone) Halite Gypsum

• Rocks that have changed due to intense temperature and pressure • “Meta” means “change” and morphosis means “form” in Greek • Igneous, sedimentary and other metamorphic rocks can change to become metamorphic rocks

What occurs in the Earth to change these rocks? • Pressure from overlying rock layers • High heat, but not enough to melt the rock • Rocks may be flattened or bent or atoms may be exchanged to form new minerals.

How are metamorphic rocks classified? Foliated—mineral grains are flattened and line up in parallel bands • Example: gneiss formed from rearrangement of minerals in granite into bands

How are metamorphic rocks classified? • Non-Foliated—No bands are formed • Example: marble formed from limestone

Where do metamorphic rocks usually form? • Where magma intrudes relatively cool rock • Near colliding plates (near mountain ranges) • Places that are covered miles thick with other rock causing pressure • When hot water intrudes rock • Where a meteorite strikes Earth (rare) • Where lightning bolts strike rocks (rare)

Examples • Some examples of how metamorphic rocks were changed: The original rock is called the Parent Rock before it is metamorphosed