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