Transcript Sedimentary rocks - Harpursville Middle School
ROCKS ROCK • Classified on the basis of FORMATION • 3 Types – Sedimentary – Igneous – Metamorphic 4/25/2020
Rocks • Composed of Minerals – Mixtures • 2 Types – Monomineralic – Polymineralic • Of the 4000 minerals, only 8 of them make up 90% of the crust.
4/25/2020
Sedimentary Rocks
• Rocks that form from the accumulation of sediments, organic material or chemical precipitates.
4/25/2020
Three main types
• Clastic –Made from fragments of other rocks • Chemical/non-clastic • Organic 4/25/2020
Clastic
(also known as fragmental) • Classified on the basis of grain size • Formation –Compaction (Pressure) –Cementation (glued) Examples 4/25/2020 –calcite –silicate
1. Layers of sediments accumulate 2. Pressure squeezes lower layers 3. Sediment becomes compacted and cemented into rock Pressure = Limestone 4/25/2020 Pressure = shale Pressure = Sandstone
4/25/2020
4/25/2020
Non-clastic (chemical) sedimentary rocks
• Formed from evaporation of water – Examples • limestone • Halite • Also known as evaporites • Precipitates also occur 4/25/2020
Organic Sedimentary Rocks
• Formed from the remains of former living things –Example: coal 4/25/2020
4/25/2020
Sedimentary Rocks
• Chemical and organic sedimentary rocks identified primarily by composition and texture (grain size) • Sedimentary rocks form relatively close to the Earth’s surface Why?
4/25/2020
Sedimentary Rocks
• All clastic sedimentary rocks are formed in horizontal layers Why do you think this is so?
4/25/2020
4/25/2020
Bedding in Sandstone and Shale, Utah
Crossbedded Sandstone, Zion Natl. Park, Utah. Formed by Sand dunes deposited by wind
Graded Bedding
Sedimentary Rocks
• Sedimentary rocks sometimes contain fossils –Igneous and metamorphic rocks almost never do Why not?
4/25/2020
Sedimentary Rocks
• Lake and ocean environments produce different sedimentary rocks –Examples: • Limestone –Forms in oceans • Sandstone –Forms in water near land 4/25/2020
4/25/2020
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?
4/25/2020