Earth and Space Science / Unit 2: Minerals and Rocks
2.5 Sedimentary Rocks
Notes
Sedimentary rocks form when sediment is deposited, buried, and turned to rock by compaction (squeezing) and cementation (minerals gluing grains). Together this is lithification.
- Clastic: made of rock fragments, named by grain size. Conglomerate (pebbles), sandstone (sand), shale (clay and silt).
- Chemical: left by evaporation (rock salt, gypsum).
- Organic: from living things. Limestone from shells; coal from plant matter.
- Sedimentary rocks show strata (layers) and are the main rocks to contain fossils.
Practice
Which process glues sediment grains together into rock?
Dissolved minerals crystallize between grains and bind them.
Which rock is most likely to contain fossils?
Sedimentary rocks preserve fossils; igneous and high-grade metamorphic rocks do not.
A rock made of rounded pebbles cemented together is:
Conglomerate has gravel-sized, rounded clasts.
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