ROCKS ROCK Classified on the basis of FORMATION 3 Types Sedimentary Igneous Metamorphic 2/4/2019
Rocks Composed of Minerals 2 Types Mixtures 2 Types Monomineralic Polymineralic Of the 4000 minerals, only 8 of them make up 90% of the crust. 2/4/2019
2/4/2019 Sedimentary Rocks Rocks that form from the accumulation of sediments, organic material or chemical precipitates. 2/4/2019
Three main types Clastic Chemical/non-clastic Organic Made from fragments of other rocks Chemical/non-clastic Organic 2/4/2019
Clastic (also known as fragmental) Classified on the basis of grain size Formation- Compaction (Pressure) Cementation (glued) Examples calcite silicate 2/4/2019
Layers of sediments accumulate Pressure squeezes lower layers Sediment becomes compacted and cemented into rock Pressure = Sandstone Pressure = shale Pressure = Limestone 2/4/2019
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Non-clastic (chemical) sedimentary rocks Formed from evaporation of water Examples limestone Halite Also known as evaporites Precipitates also occur 2/4/2019
Organic Sedimentary Rocks Formed from the remains of former living things Example: coal 2/4/2019
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Sedimentary Rocks Why? Chemical and organic sedimentary rocks identified primarily by composition and texture (grain size) Sedimentary rocks form relatively close to the Earth’s surface Why? 2/4/2019
Sedimentary Rocks Why do you think this is so? All clastic sedimentary rocks are formed in horizontal layers Why do you think this is so? 2/4/2019
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Bedding in Sandstone and Shale, Utah
Crossbedded Sandstone, Zion Natl. Park, Utah Crossbedded Sandstone, Zion Natl. Park, Utah. Formed by Sand dunes deposited by wind
Graded Bedding
Sedimentary Rocks Why not? Sedimentary rocks sometimes contain fossils Igneous and metamorphic rocks almost never do Why not? 2/4/2019
Sedimentary Rocks Lake and ocean environments produce different sedimentary rocks Examples: Limestone Forms in oceans Sandstone Forms in water near land 2/4/2019
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Use your ESRT to answer the following questions. What is the composition of rock salt? What is the size range of the grains in sandstone? Draw the map symbol of shale Which is made of rounded fragments, conglomerate or breccia? 2/4/2019