sedimentary rocks. did you know? 75% of rocks exposed at earths surface are sedimentary sedimentary...
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Sedimentary RocksSedimentary Rocks
Sedimentary RocksSedimentary Rocks
DID YOU KNOW?DID YOU KNOW?
75% of rocks exposed at Earths surface are sedimentary
Sedimentary rocks form in various regionsoceans, lakes, rivers, beachesglaciated areasdeserts
Sedimentary Rock
• Sedimentary – Formed in layers as a result of pressure on sediments (small pieces of rock)
• Sediments settle in low places, usually near or under bodies of water.
• No Heat involved in formation
Sedimentary Rocks • Over time the sediments form
layers that are compacted together over time and form rocks.
• Sedimentary rocks are almost always found in layers
StrataStratification – the process in which sedimentary rocks are arranged in layers
Form By Three Main ProcessesForm By Three Main Processes
Compaction- Sediments get compressed andcompacted.
Cementation-Small crystals precipitate and act as glue that holds the rock together.
Precipitation-Crystals precipitate directly from solution.
Sedimentary RocksSedimentary Rocks
There are 3 Types…
• Clastic – formed from weathering debris
• Chemical – form when dissolved materials precipitate from solution
• Organic – form from the accumulation of plant or animal debris
ClasticBreccia
Conglomerate
Contains large angular fragments
Large rounded fragments
Sandstone
Shale
Sand-sized debris, often found around beaches and deserts
Made of clay-sized debris, often breaks into flat pieces
Chemical
Limestone – forms chemically from precipitation of calcium carbonate from lake or ocean water
Rock salt – forms from the evaporation of ocean or saline lake waters. Rarely found at Earth’s surface
OrganicCoal – Forms from Plant Debris – Often found in Swamp areas