The Rock Cycle
A. Igneous Rocks
C. Metamorphic
B. Sedimentary
Melted rock cools and hardens underground or as lava
Higher pressures and temperatures cause rocks to melt
Higher pressures and temperatures
Weathering and Erosion
Sediments
Buried, compacted, and changed into rock
Higher pressures and temperatures
To the surfaceTo the surface
Igneous Rocks
• “From Fire”
• Made from molten rock
• This rock’s temperature is so hot that it melted.
www.usgs.gov
Igneous Rocks
• Two types of igneous rocks:– Rocks made from Magma (underground)– Rocks made from Lava (above ground)
www.windows.ucar.eduwww.usgs.gov
Intrusive Igneous Rocks• Intrusive igneous rocks are made underground
out of magma.• Since they are not ever exposed to air or water,
they cool very slowly. This allows minerals in the rocks time to form large crystals.
• These rocks are also called coarse grained rocks because they have large crystals.
• Most common intrusive igneous
rock is granite.
www.panet-terre.com
Extrusive Igneous Rocks• Made on the surface of the Earth out of lava.• These rocks cool quickly (small or no crystals).
Sometimes the lava cools so quickly that bubbles form from escaping gas. Some rocks are more than 50% holes!
• If the lava cools rapidly in water, the resulting rock can look like glass.
Obsidian Pumice
Sedimentary Rocks
• Rocks made from sediments that were either pressed together or cemented together.
• Most sedimentary rocks form under water.
www.earthsci.org
Sedimentary Rocks
• Layers of sediment compacted and cemented
www.usgs.gov
www.calstatela.eduSandstone
Limestone along the Katy Trail
Types of Sedimentary Rocks
• Clastic – composed only of rock fragments
• Organic – rocks that contain organic, or once material that was once living.
• Chemical rocks formed by a chemical process.
Clastic Sedimentary Rocks
• Rocks that are exposed at the surface of the Earth are subjected to weathering. This breaks the rocks into smaller pieces.
• The process of erosion then moves the pieces to another location where they are deposited.
• These pieces become compressed and cemented together to form a clastic sedimentary rock. The size of particles that make the rock is what identifies the rock type.
Non-Clastic Sedimentary Rocks• Organic – are made either directly or
indirectly from material that was once alive.
• Examples of materials that make up organic rocks are leaves and shells.
seis.natsci.csulb.edu
Non-Clastic Sedimentary Rocks Continued
• Chemical - Formed by a chemical process that do not involve living organisms.
• An example of these would be would be evaporites, which form when water evaporates out of a solution leaving the minerals behind.
• When the element Calcium (Ca) and the compound Carbonate (CO3) get dissolved in water, the water evaporates, the mineral Calcite (CaCO3) is left behind.
www.caverntours.com
Bonneville Salt Flats
When water containing sodium and chloride evaporates, the mineral Halite is left behind.
Metamorphic Rocks
• Meta- Change
• Morph- Form
• Metamorphic rocks are rocks that have changed form due to tremendous heat, great pressure, and chemical reactions.
• The mineral crystals in the rocks may change their size or shape, or become separated into layers.
Examples of Metamorphic Rocks
• Shale Slate
• Limestone Marble
• Sandstone Quartzite
Heat & Pressure
Heat & Pressure
Heat & Pressure
Foliated Metamorphic Rocks• Mineral crystals are arranged in parallel
bands. Rocks can break along these bands.
GneissSlate
Slate
Unfoliated Metamorphic Rocks
• Do not have bands of crystals and do not break into layers.
SerpentintiteMarble