4-3 Sedimentary Rock—usually forms under water
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Transcript of 4-3 Sedimentary Rock—usually forms under water
4-3 Sedimentary Rock—usually forms under water
notice the layers (stratification)
From Sediment to Rock
Formed from sediments=small, loose solid pieces of material that come from weathered rock or living material•formed in layers (may not be visible)•May contain fossils•examples of sediments:
– shells, bones– mud, gravel– sand, clay
How do sediments build up?
• Observe how sediments are deposited (website)
Sediments accumulate in layers at the bottoms of lakes or oceans
(called deposition)
(examples—not to memorize)
• sand becomes……………sandstone• gravel becomes………….conglomerate• mud & clay becomes…….shale
2 forces that make the sediments into rocks (can take millions of years)
• 1--Compaction– press sediment
together and squeezes out the water
(PRESSURE)
• 2--Cementation– dissolved minerals
crystallize and glue particles together (natural glue)
(GLUED TOGETHER)
PERFORMANCE TASK #4
Texture of Sedimentary Rocks
3 types of sedimentary rocks (look at the type of sediment)
• 1--clastic• 2--organic• 3--chemical
Clastic=broken pieces glued together (need to look at size of pieces)
• Shale– tiny pieces of clay– thin, flat layers– feels smooth– due to compaction
• Sandstone– forms on beaches, ocean floors, in
riverbeds, or sand dunes– fairly small pieces of sediment– due to compaction & cementation
• Conglomerate and Breccia– variety of particle
sizes– conglomerate=round
– breccia= sharp edges
2 other types of sedimentary rocks• Organic-from ancient plants
and animals {many extinct-may have fossils}– coal=remains of swamp
plants (over millions of years old)
– limestone=from shells and skeletons of ancient sea animals, which contain calcite (coral, clams, oysters, snails)
• Chemical Rocks– limestone forms
when dissolved calcite comes out of solution and forms crystals
– rock salt and gypsum form from evaporation (in dry climates)
Performance Tasks Number FIVE and EIGHT…
• Can now be completed
• Make sure you completed 5 & 8!
Questions• What natural activities work to break down rock?• weathering • What do sand and mud become when they form
sedimentary rock?• Sandstone, shale and mudstone• In what type of rock would paleontologists look
for fossils?• (organic) sedimentary –like limestone
Question--{enrich}
• A layer of a sedimentary rock is 2 meters (2000 mm) thick. How many years did it take for this layer to form if an average of 4mm of sediment accumulated each year?
• >> 500 years