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Transcript of Es8
Sedimentary rocks, pt2
Sedimentary rocks
1. clastic
2. chemical
3. organic
Sedimentary rocks: chemical rocks
Sea, lake, swamp, and other waters contain dissolved minerals.
Chemical sediments are formed when these minerals fall out of solution: Evaporation Chemical reaction
Chemical rocks
1. limestones of chemical origin: from tiny grains of calcite
2. rock salt
3. gypsum
limestone
Rock salt
gypsum
Sedimentary rocks
1. clastic
2. chemical
3. organic: formed from the remains of animals and plants.
E.g. limestone and coal
limestone
usually an organic sedimentary rock that forms from the accumulation of shell, coral, algal and fecal debris.
It can also be a chemical sedimentary rock formed by the precipitation of calcium carbonate from lake or ocean water.
limestone
Contain calcite, so they can be identified by the acid test.
Fossils
Fossils
Fossils are remains or impressions of plants and animals in rock
Skeletal structures remain, or are replaced by minerals in their shape.
Found in sedimentary rocks. (Why not in igneous rocks?)
geodes
geodes
1. Water dissolves some limestones, creating cavities within.
2. The groundwater deposits quartz or calcite crystals in the cavities.
concretions
concretions
Concretions are rounded rocks embedded in layers of stone in sedimentary rocks. They are often harder than the surrounding rock and weather out of the host rock. They are often spherical or nodules. Nodules are often shaped like potatoes.