sedimentary rocks deposition. origin of sedimentary rocks most common rocks on the earth are...
TRANSCRIPT
Sedimentary Rocks
deposition
Origin of Sedimentary Rocks
• Most common rocks on the earth are igneous.
• 2nd common sedimentary
Sedimentary Rock
• Rocks formed from sediments– 1. Sediments cemented
together (detrital)
– 2. Fall out of solution as a precipitate (chemical)
– 3. plant material pressed together (organic)
Sediments are:
• Pieces of minerals
• Pieces of rock
• Pieces of organic matter
• Minerals dissolved in water – in solution
Detrital Sedimentary Rocks
• Also known as clastic sedimentary rocks
• From Greek klastos, broken;
• Detrital or clastic sedimentary rocks are rocks made from broken pieces of other rock that have been cemented together to form a new rock
Sizes of sediment designation kind of rock formed
(copy chart in notebook)
How sedimentary rocks are formed
Strata – layers of rock
• • Millions of years have gone by and
there are many layers of deposited sediment now.
• Some of the sediment granules have been cemented together by minerals that were dissolved in the water.
• They have turned into layers of rock.
Compaction
• Pressure from the upper layers of sediments squeeze out water.
• Reduce the spaces between the particles
• They become packed together more tightly.
• New rock formed
Cementation • Water soaks through soil
• Dissolves minerals such as calcite, hematite and limonite (kinds of cement)
• Solution moves through open spaces between sediment and fills spaces
• Minerals fall out of solution (precipitate – solid left from solution)
• “cement” the sediment together.
• New rock formed
Calcite, hematite, limonite areKinds of cement.
Classification of Sedimentary Rocks
• `1. Detrital Sedimentary Rocks – Clastic
• Lt. Detritus – to wear away
• Made from broken fragments of other rocks. Compacted and cemented together.
• Clastic Gr.klastos – broken
conglomerate
• Rounded gravel sized sediments cemented together
Breccia
• Angular sediments that are cemented.
• Found at talus slopes
Talus slope
Sandstone
• Sand sized sediment cemented together
Shale
• Clay sized sediment held together by compaction.
Coquina
• Beach pebbles, shells and animal bodies cemented together
• Found along shores
Chemical Sedimentary Rocks
• 2. chemical sedimentary rocks
• Minerals precipitated out of a solution.– (falls out of solution
when water evaporates)
• Calcite in caves
• Halite – salt mines ancient salt seas
Limestone
• Calcium carbonate (CaCO3) carried in ocean water dissolved from animal shells.
• Deposited on sea or ocean floors
• Precipitates out of solution.
• Precipitate – any solid that comes out of solution
Rock salt
• Found in evaporated salt water lakes or seas.
• Precipitates out when water is evaporated
Fossiliferous limestone
• Limestone with fossils.
• Found in old salt water lakes, bays, seas
Chalk
• Smashed microscopic shell bodies of sea animals.
• compacted
Coal
• Decayed organic matter that had been compacted to form a rock.