Rocks
Alexis Shatesky
Rock Types
A rock is the solid mineral material forming part of the surface of the earth and other similar planets, exposed on the surface or underlying the soil or oceans.
Igneous
- Formed by cooling and crystallization of molten rock
- Melts and solidifies and forms crystals
- Fast cooling: small crystals
- Slow cooling: big crystals
- Intrusive rocks crystallize slowly inside the earth's crust
- Extrusive rocks crystallize quickly at earth's surface
Sedimentary
- Weathered remains of other rocks
- Formed by compaction and cementing of sediments
- Found on earth's surface
- Contains fossils
- Clastic rocks are made of different sized particles cemented together
- Biosclastic rocks form by accumulation of plant and animal remains
- Crystalline rocks are deposited when chemicals in seawater precipitate and fall to the ocean bottom
Metamorphic
- Heat and pressure without melting
- Foliation: alignment of minerals in a metamorphic rock
- Banding: type of foliation that is wavy colored stripes
- Regional metamorphism: large masses of rock changed by deep burial within earth
- Contact metamorphism: chemical and physical change to a rock caused by nearby intrusion or extrusion of molten rock
Examples of Rock Types
Gabbro
- Forms beneath earth's surface
- Coarse grain
- 1 mm or larger
- Darker color
- Higher density
- Non-vesicular
- Mafic
- 35% plagioclase feldspar
- 55% pyroxine
Limestone
- Formed by skeletal fragments of marine organisms
- Formed near water
- Organically formed
- Crystalline or bioclastic
- Precipitates of biologic origin or cemented shell fragments
Metaconglomerate
- Breaks through the grains as cement recrystallized
- Coarse texture
- Nonfoliated
- Regional or contact
- Pebbles may be distorted or stretched
The Rock Cycle
Model showing how rocks and sediments change over time.
- External processes occur on earth's surface
- Internal processes occur within the earth