Rocks And the Rock Cycle

The Rock Cycle

Rock Cycle

Rocks A mixture of minerals, mineraloids, glass, or organic matter. A mixture of minerals, mineraloids, glass, or organic matter. Three main types of Rock Three main types of Rock –Igneous –Metamorphic –Sedimentary

The Rock Cycle The changing of rocks from one form to another by processes such as weathering, erosion, compaction, cementation, melting, and cooling.

Igneous Rocks

Igneous Rock

The beginning of the Rock Cycle

Igneous Rocks Starts as MAGMA… rock that has melted from pressure and heat in the Earth Starts as MAGMA… rock that has melted from pressure and heat in the Earth Pressure and heat build Pressure and heat build Magma rises to surface Magma rises to surface Comes out in Volcano as LAVA Comes out in Volcano as LAVA

Intrusive Vs. Extrusive Rocks form below Earth’s surface Rocks form below Earth’s surface Cool slowly Cool slowly Large crystals form Large crystals form Examples Examples –Granite –Diorite –Gabbro Rocks form when lava cools on or near Earth’s surface Fast cooling Small crystals form Examples –Obsidian –Pumice –Basalt

Intrusive

Granite Notice the crystals Notice the crystals The crystals are pieces of mineral The crystals are pieces of mineral

Diorite

Gabbro

Extrusive

Obsidian

Rhyolite

Pumice

Basalt

Scoria

Andesite

Three Compositions that effect Igneous Rock Types BasalticGraniticAndesitic Dense, heavy Dark Colored Rich in Fe, Mg Hawaii Light Colored Lower Density Thick and Stiff Lot of Si, O Violent Eruption Halfway between other two

Igneous Rock Types

Basaltic

Andesitic

Granitic

Metamorphic Rocks

Rocks that have changed due to temperature and pressure increases or that undergo changes in composition Rocks that have changed due to temperature and pressure increases or that undergo changes in composition Can be formed from: Can be formed from: –Igneous Rocks –Sedimentary Rocks –Metamorphic Rocks

Formation of Metamorphic Rocks Rocks beneath the surface under pressure and heat Once reach critical pt, rocks melt Or mineral grains are flattened New rocks formed by combination of processes

Classification of Metamorphic Foliated Foliated When mineral grains flatten and line up in parallel bands When mineral grains flatten and line up in parallel bands –Slate –Gneiss Nonfoliated When no banding occurs during formation –Quartizite –Marble

Before and After Shale Shale Slate

Before and After Granite Granite Gneiss

Before and After Sandstone Sandstone Quartzite

Before and After Limestone Limestone Marble

The Rock Cycle Now

Sedimentary Rocks

Sediments and Sedimentary Rocks Sedimentary rock are made when sediments become pressed or cemented together or when sediments precipitate out of a solution Sedimentary rock are made when sediments become pressed or cemented together or when sediments precipitate out of a solution Sediments are loose materials such as rock fragments, mineral grains, bits of plants and animals that have been moved by wind, water, ice, or gravity Sediments are loose materials such as rock fragments, mineral grains, bits of plants and animals that have been moved by wind, water, ice, or gravity

How they are made 1 st wind and/or water erode existing rock 2 nd wind, water, ice, or gravity move sediments to a new location 3 rd new rocks are made by compaction or cementation

The two C’s that make Sed. Rock Compaction: after erosion has moved sediment to new location, pressure from upper layers pushed down on lower layers and small sediments stick together Compaction: after erosion has moved sediment to new location, pressure from upper layers pushed down on lower layers and small sediments stick together Cementation: from large sediments, water socks through soil and rock and dissolves minerals (calcite, hematite, & limonite) these fill small spaces in-between and harden