ROCKS By Gina Wike

ROCKS A rock is defined as a mixture of minerals, mineraloids, glass, or organic matter

Rock-forming Minerals 1. Quartz- one of the 2 most abundant minerals 2. Feldspar- one of the 2 most abundant minerals 3.Hornblende 4.Mica

3 TYPES OF ROCKS Igneous Metamorphic Sedimentary

THE ROCK CYCLE The rock cycle shows that any rock, whether it be igneous, metamorphic, or sedimentary, can change into another type of rock depending upon the processes that change them

Rock-changing Processes Weathering Erosion Compaction Cementation Melting Cooling

Rock Changing Processes SEDIMENTARY Weathering Erosion Compaction Cementation The compaction and cementation of sediments form sedimentary rocks. Weathering of rock forms sediments. Erosion then moves the sediments.

Rock Changing Processes METAMORPHIC Heat Pressure Heat and pressure change rocks into metamorphic rocks. Even metamorphic rocks can change into different metamorphic rocks when heat and pressure are added.

Rock Changing Processes IGNEOUS Melting Cooling The cooling of melted rock (magma or lava) forms igneous rock.

Rocks that form from magma or lava

Igneous Rocks Igneous rocks form when molten material (magma & lava) cools Magma is less dense than the surrounding rock, so it rises. When magma cools slowly, there are LARGE crystals or mineral grains. When magma cools quickly, the grains or crystals are small- even microscopic.

IGNEOUS ROCKS Igneous rocks can be classified by where they form (LOCATION) Intrusive Igneous Extrusive Igneous

Intrusive Igneous Rocks Form below the Earth’s surface; inside the Earth Crystals are large because the magma cools slowly Coarse-grained Found at the earth’s surface only when forces inside the Earth push them up or when weathering & erosion expose them

INTRUSIVE IGNEOUS Example: Granite is an intrusive igneous rock

EXTRUSIVE IGNEOUS ROCK Found at the earth’s surface Crystals are small because the lava cools quickly Fine-grained or small-grained Examples: Obsidian & pumice

OBSIDIAN Obsidian looks like black glass.

Pumice Pumice floats in water because it is less dense than the water. Pumice has holes in it from where gas escapes as the molten material cools. It is used in hand cleansers because of its abrasive quality.

IGNEOUS ROCKS Igneous rock can be classified by the type of minerals in the magma or lava Basaltic Andesitic Granitic

BASALTIC ROCKS Made of basaltic magma or lava Rich in iron and magnesium Dark-colored Heavy Dense

GRANITIC Made of granitic magma or lava Rich in silicon & oxygen Light-colored Lower in density

ANDESITIC Composition between that of basaltic and granitic

IGNEOUS ROCKS Igneous rocks are the most abundant on Earth Basalt is the most common extrusive igneous rock.

METAMORPHIC ROCKS Form from heat & pressure

METAMORPHIC ROCK Metamorphic rocks are formed when heat and pressure are added to sedimentary, igneous, and even metamorphic rocks. One type of rock can change into several different rocks, depending upon the amount of heat and pressure applied.

METAMORPHIC ROCKS Metamorphic rocks have 2 classifications: Foliated & Nonfoliated

FOLIATED This is when mineral grains flatten and line up in parallel bands These rocks will separate easily between the layers Examples: Gneiss & Slate Folded foliation pictured below:

Slate Slate forms when heat and pressure are applied to shale. Slate is used in roofing because it separates easily into layers.

NONFOLIATED No banding or parallel layers Mineral grains change, grow, or rearrange Nonfoliated rocks fracture into pieces of random size. Example: marble

METAMORPHIC ROCKS Original Rock Rock Type of Original Rock Metamorphic Rock Formed LimestoneSedimentaryMarble SandstoneSedimentaryQuartzite ShaleSedimentarySlate GraniteIgneousGneiss

SEDIMENTARY ROCKS Form from compaction and cementation of sediments

SEDIMENTARY ROCKS 75% of rocks at the Earth’s surface are sedimentary rocks Sedimentary rocks form when sediments become pressed or cemented together. Sediments are loose material such as rock fragments, minerals, and bits of plant and animal remains. Weathering is the process that breaks rock into smaller pieces. Erosion is the movement of sediments.

SEDIMENTARY ROCKS If sediments are small, they can be compacted or packed together to form sedimentary rocks. This process is compaction. If sediments are large, they must be glued or cemented together. Minerals mix with water to form natural cement or glue. This process is cementation.

SEDIMENTARY ROCKS Sediment sizes: (smallest to largest) clay- smallest silt sand gravel- largest

SEDIMENTARY ROCKS Sedimentary rocks form as layers, or strata. Sediments are put down horizontally. The oldest layers are on the bottom.

SEDIMENTARY ROCK Classification of rock layers Clastic Chemical Organic

CLASTIC Named by shape & size of sediment Large sediments: 1. Conglomerate 2. Breccia Small sediments: 1. Shale 2. Sandstone

CHEMICAL Form when sediments precipitate out of a solution Examples: 1. Rock salt 2. Limestone

ORGANIC Form from once-living things Examples: 1. Fossil-rich limestone 2. Coquina 3. Chalk 4. Coal