Identifying Rocks Sedimentary rocks
Rocks are partly identified by origin: • Igneous • Sedimentary • Metamorphic
Wow! • Seventy percent of all the rocks on earth are sedimentary rocks.
How are sedimentary rocks formed? • Several Steps • Erosion • Deposition • Compaction • Cementation
Erosion/Weathering • Occurs when running water or wind loosens and carries away fragments of rocks.
Erosion • Erosion is the breakdown of the continents and the land around you.
Erosion is destructive!!! What causes erosion? • Wind, water, heat, cold, rain, waves, grinding ice
Boulders become sand. Mountains are rained on and become hills. The pieces of the mountain become smaller pieces and go down the sides of hills. Weathering and erosion always happen in a downhill direction.
2. Deposition When the sediments settle out of the wind or water. The Sediment will sink to bottom of lake or ocean
The sediments are deposited into a body of water like you are depositing money in a bank
Compaction • It is a process • Thick layers of sediment build up • Layers become heavy and press down on layers beneath • Sediments are pressed together
3. Cementation • Word connection- cement • First Minerals in rock dissolve • Next, cement seeps into spaces between particles • Then, dissolved minerals crystallize and GLUE the particles together
Compaction and Cementation • These processes cause loose sediments to turn into rocks • This takes millions of years!!!! • http://www.classzone.com/books/earth_science/terc/content/visualizations/es0604/es0604page01.cfm?chapter_no=visualization
grains of different sizes settle under the action of gravity. • adding the pressure causes compaction (center). • Cementation (right) is one of the final processes that turns sediment into rock.
Types of Sedimentary Rocks Clastic- formed by rock fragments squeezed together
Conglomerate is a sedimentary rock • contains rounded particles/pebbles that are cemented together • Has a large range of particle sizes
Organic • made from living things (coral, clams, oysters, snails, shells, skeletons, leaves) • Coal • Limestone(chalk)
Chemical • when minerals dissolve in a solution and crystallize • Calcite to limestone • Halite to mineral salt • gypsum
In September, 2012, NASA's Mars rover Curiosity discovered an outcrop of conglomerate exposed on the surface of Mars