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