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RocksRocks
Adapted from: Dr. Michael J. Passow
Sedimentary RocksSedimentary Rocks
• Consist mainly of weathered rock debris which have become compacted and cemented
• Cover about ¾ of Earth’s surface
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks6.html
Sediment Sizes
Gritty in your teeth
Clastic texture - made of cemented (lithified) sediments,classified by their grain sizes
Ex. Shale – the most common sedimentary rock
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks9.html
Chemical sedimentary rocks form by chemical precipitation (evaporation of water)
Ex. - Limestone is made from calcite, chert from quartz, and rock salt is halite.
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks10.html
Biochemical/Organic sedimentary rocks – come from the remains of organic matter
• Lignite, Bituminous, Anthracite coal results from the greatest pressure and releases the most energy when burned.
• Coquina forms from sea shells
• Fossiliferous limestone formed from shell fragments
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks11.html
IGNEOUS ROCKS
• Form from crystallization of magma
• EXTRUSIVE – formed from lava– Fine-grained (small) crystals– Glassy (no crystals)
• INTRUSIVE - formed from magma– Coarse-grained (large) crystals
Aphanitic Texture
- Crystals are uniformly fine-grained
- Individual crystals invisible to the unaided eye
- Magma cooled rapidly
Ex. - Basalt
Porphyritic Texture
-Large crystals (phenocrysts) are surrounded by an aphanitic matrix (groundmass)
- 2 rates of cooling
Ex. – Diorite porphyry
Vesicular Texture
- Vesicles are holes produced by gases escaping from lava as it solidifies
- Cooled rapidly Ex. - Scoria
Glassy Texture
- Very rapid cooling - Volcanic glass
Ex. - Obsidian
Phaneritic Texture
- Large crystals
- Cooled slowly, underground
- Individual minerals are evident
Ex. - Diorite
Metamorphic RocksMetamorphic Rocks
• Formed by heat and pressure changing existing rocks
• REGIONAL METAMORPHISM affects a large area and results from plate tectonics
• CONTACT METAMORPHISM affects rocks on a local scale, such as “baking” sedimentary rocks next to magma or lava
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Metrocks/Metrocks1.html
“Foliated” texture show layering or banding
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Metrocks/Metrocks5.html
Non-foliated texture rocks include marble, which comes from limestone, and quartzite, which comes from sandstone
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Metrocks/Metrocks12.html
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Rocks/Rocks8.html
Rock Cycle
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Metrocks/Metrocks2.html