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