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Sedimentary Rocks. What is a Sedimentary Rock?. Comes from the word “sediment”. Means “something that settles” Loose material gets naturally cemented together and forms a rock. What is sediment?. Plant Remains Animal Remains Salts. Boulders Gravel Sand Silt Clay. Suspension.
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What is a Sedimentary Rock? • Comes from the word “sediment”. • Means “something that settles” • Loose material gets naturally cemented together and forms a rock.
What is sediment? • Plant Remains • Animal Remains • Salts • Boulders • Gravel • Sand • Silt • Clay
Suspension • Rivers move sediment along. • Less dense sediment (silt/clay/animal and plant remains) may be suspended in the water. • More dense sediment (rocks/boulders) roll along the bottom.
Forming New Sediments • Look at the rocks at your table. • What can you say about the shape of the rocks? • Along a river, those sharp corners are rubbed off. Those new, smaller sediments will be mixed and form new sedimentary rocks.
As the river widens • There is the same amount of water. • Velocity is slowed. • Since the velocity is slowed, it cannot carry many of the sediments and they settle to the bottom.
Some Rocks Made by Plants or Shells • Coal • Dead plants fell on older, dead plants • Sediment covered them. • The pressure over millions of years created coal.
Limestone • Made from carbonate materials. • Such as calcite • Shells and skeletons of ocean animals formed these minerals. • Over time, their shells are buried on the ocean floor, covered by sediment and cemented together to form limestone.
Dover Cliffs of England • Developed millions of years ago when they were under the ocean.
Review • What is a sediment? • What is “suspension”?
Review • What are the two ways, that we have learned, that sedimentary rocks form? • What are two rocks that do not form from other rocks?
Dissolved Minerals Reform • Rain water washes over minerals and moves them. • Some are dissolved in water. • Water flows through cracks in rocks and dissolves the rock. • This creates caverns.
Sedimentary Rocks Show the Effects of Wind and Water • Sedimentary rocks laid down in layers. • Older layers are on the bottom. • Fossils can get trapped in a layer and covered by the next layer. • Rocks can also show conditions long ago.
