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 SEDIMENTARY METAMORPHIC Weathering, Erosion, Compaction, Cementation Heat and Pressure Weathering, Erosion, Compaction, Cementation Heat and Pressure Melting, Solidification Igneous SedimentaryMetamorphic

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

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

Peridotite: Intrusive or Extrusive? Why?

Granite: Intrusive or Extrusive? Why?

Porphyry: Intrusive or Extrusive? Why?

Obsidian: Intrusive or Extrusive? Why?

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.

Sedimentary rocks represent 7% of the Earth’s crust, but they cover 70% of the Earth’s surface. Sedimentary rocks are fossil-carrying rocks.

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)

How can sedimentary layers help us understand the age of fossils? As sedimentary rocks are deposited, they form horizontal layers Scientists know that the layers on top (and the fossils in the top layer) are YOUNGER than the fossils in lower layers.

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

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 3 Types of Sedimentary Rocks: COQUINA FOSSILIFEROUS LIMESTONECHALK

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

*You can think of metamorphic rocks as a squished peanut butter & jelly sandwich in your lunch.

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