The Cycle let’s review some basic information … TheRockThe RockTheRockThe Rock The Rock Cycle Adapted from a Powerpoint by Michigan Department of Environmental Quality Geological Survey Division -

Natural elements and compounds are minerals. Rocks are mixtures of minerals. Rocks make the Earth Elements combine to make compounds.

Sedimentary Rocks Metamorphic Rocks Igneous Rocks The Earth is made of 3 kinds of rock that are recycled in the Rock Cycle

Igneous Rocks

Sedimentary Rocks

Metamorphic Rocks

Enough about rocks, on to the cycle …

James Hutton Developed the Rock Cycle explaining that rocks don’t stay the same forever; natural physical processes cause them to change from one type to another.

weathering melting pressure, heat Sedimentary Metamorphic Igneous The Rock Cycle. Rocks are neither created nor destroyed, they just change from one type to another. The Rock Cycle does not go in just one direction. Any given rock can go through any part of the cycle any number of times.

March 2000 The Earth can be thought of as a giant recycling machine

Google “rock cycle” Rock cycles

Igneous Rocks

Formed from molten material

Igneous= made from fire Igneous rocks start as molten rock or magma which may become solid before ever reaching the surface Sometimes magma is full of gases like a pop with the cap on. When magma reaches the surface pressure is released, gases begin escaping and it’s lava Mt. St. Helens Videocam

Igneous Rock Crystals interlock (grew together ) forming a strong rock. Magma cools slowly and crystals have time to grow. Lava cools quick and the crystals don’t have time to grow so they’re small or there are none. Bigger crystals = slower cooling = deeper

Crystal Size Rate of cooling determines size of crystals Fast cooling: no crystals or small crystals Slow cooling: large crystals

Extrusive: Cool Fast No Crystals.

Extrusive: Cool Fast Small Crystals

Examples: Extrusive Obsidian

Examples: Extrusive Pumice

Examples: Extrusive Basalt

Intrusive: Cool slowly Large crystals

Examples: Intrusive Granite

Clues it’s Igneous If crystals are large, the colors are randomly spread. If crystals are small, the color is even and there may be an occasional big crystal May have bubbles May be made of broken fragments May be glass.

Sedimentary Starts with Rocks Being Broken into Smaller Pieces Heating and cooling causes rock to expand and shrink. Water gets into cracks, freezes and expands, splitting the rock. Lichens & plants make acids that dissolve rock. Plant roots split rock. A process called weathering

Weathered Rock Erodes Wind, water and gravity, cause weathered rock to erode Eroding fragments of rock get smaller and more rounded the more they erode. Faster water can carry bigger fragments, pieces settle out as the current slows and the water deepens. Sediment Deposition

Sediment Becomes Rock New layers are always on top of old layers Sediment builds up and increased weight causes sediment to compact Minerals grow between compacted pieces turning them into rock

Sedimentary Rocks

Sed. Rocks often form into layers

From Sediment to Rock Most sedimentary rocks are formed through a series of processes: erosion, deposition, compaction, and cementation.

Clues it’s Sedimentary Earthy colors (browns, oranges, reds, black, gray, white, clear, sand, mauve, buff, tan, etc.) Rounded pieces Fossils

Metamorphic Rocks metamorphic Pressure, heat and fluids cause preexisting materials to become metamorphic rocks Metamorphic mountain ranges like the Rockies, Alps and Himalayas are caused by colliding plates Metamorphism Himalaya formation

Metamorphic Rock Metamorphism: Changing of one type of rock to another by: Heat Pressure Chemical reactions Metamorphism makes rocks stronger or more resistant

Contact Metamorphism –hot magma pushes through existing rock, heating surrounding rock and changing it to metamorphic.

Classification of Metamorphic rock Foliated & Non-foliated

Foliated Rocks: Have visible layers Mineral grains are flattened and aligned when pressure is added PRESSURE

Gneiss has banded foliation Granite Gneiss

Slate has banded foliation Shale Slate

Non-foliated Rocks: These DO NOT have layers of crystals.

Quartzite has no foliation (layers) SandstoneQuartzite

Marble has no foliation (layers) Limestone Marble

Finished Marble Unfinished Marble

Clues it’s Metamorphic Often black and white, or green. May be red (garnet) or shiny (mica) Often foliated (lines)