Sedimentary Rocksmslianne.weebly.com/uploads/3/9/0/5/3905138/earth_ch_6.3.pdf · Sedimentary rocks are formed from the broken down pieces of other rocks, minerals, and organic material

Chapter 6.3

Sedimentary Rocks

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Output: Sedimentary Rock

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1. Add water, so that the flask is filled to 400 ml.

2. Shake the flask quickly back and forth, and then turn them while the water is still churning, so that the cork end is down.

3. Stop shaking.

4. Observe the sand, and answer the following questions.

Where are the larger particles and why? Are there just large pieces at the bottom? As you look higher in the flask, what is happening to the size of the sand

grains? Did all of the particles settle out right away? When a river enters the ocean, the water slows down suddenly just like

when you stop shaking the flask. Which particles would you expect to drop closest to the mouth of the river?

If you were to sample the sand near a rivers mouth and then take another sample farther out to sea, what would you expect to find?

What would settle out even farther than the sand?

Output cont’d

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Draw a diagram that shows where shells/limestone, gravel/

conglomerate, silt/shale, sand/sandstone would end up.

Ex.

Sedimentary rocks are formed from the broken down pieces

of other rocks, minerals, and organic material

Characteristics are determined by sediment source, the way

it was moved, and how it was deposited

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Formation

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COMPACTION is when sediments are squeezed together

CEMETATION is when sediments get glued together by

minerals left by water

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Three classes of Sedimentary Rock

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1. Chemical Sedimentary Rocks

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CHEMICAL SEDIMENTARY ROCKS forms from minerals

once dissolved in water

If water evaporates it leaves behind minerals and forms rocks

(called evaporites)

Ex. Halite and Gypsum (rock salt)

9Bonneville Salt Flats, Utah

2. Organic Sedimentary Rocks

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ORGANIC SEDIMENTARY ROCKS are ones formed by

remains of once living things

Ex. Coal, limestone, chalk

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3. Clastic Sedimentary Rocks

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CLASTIC SEDIMENTARY ROCKS are formed when

sediments are deposited by wind, water or ice

You get different types because of the size and shape of

sediments

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Conglomerate is with rounded sediment

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Breccia is if the sediments are angular

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Sandstone is when the sediments are sand sized

Usually made of Quartz

Has small pores so water, natural gas and oil move through

them

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Shale is when the grains are clay sized and form sheets

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Characteristics

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Sorting

The sorting of the sediments is a result of how fast the

sediment was moving

You can have poorly sorted all the way to very well sorted

sediments

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Angularity

The farther the sediment moves from where it broke apart

means it will tend to be rounder and smoother

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Sedimentary Rock Features

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The setting where the rock is formed is called the

depositional environment

Each environment has different characteristics

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Stratification

Stratification is the layering of rocks

Tells a story of what the area was like as it was deposited, like

lake or river

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Cross-beds and grading beds

You can get unique shapes like cross-beds where layers cross

over each other

You can also get graded bedding where small sediments sit on

larger sediment

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Ripple Marks

Ripple marks in rocks are left by wind or water

It means the rock was formed in a river or beach

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Mud Cracks

Happens when mud dries and shrinks

Usually in flood plains

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Fossils and Concretions

Fossils can be left behind and get buried by sediments

Concretions are when you find a different material in a rock,

like a geode

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