Sedimentary Rocks

What are Sedimentary Rocks?

• Sediment- fragments of rock that

have been broken down as a result

of weathering and erosion by wind,

water, and ice.

• Sedimentary Rock- formed by the

accumulation and

cementing/compacting of

sediments.

Types of Sedimentary Rocks

• There are 2 types of sedimentary

rocks:

• Clastic sedimentary Rocks

• Chemical Sedimentary Rocks

Clastic Sedimentary Rocks

• Clastic Rocks- Form from compacted sediments.

• They are inorganic.

• Classified by the size of the sediment.

• Shale- smallest grains

• Siltstone

• Sandstone

• Breccia

• Conglomerate- largest grains

Shale

Conglomerate

Chemical Sedimentary Rocks

• Chemical Rocks- Made from the

precipitation of water.

• This is broken down into 2

categories:

• Crystalline

• Organic

Crystalline Sedimentary Rocks

• Crystalline Rocks- Form from a chemical process.

• Also known as evaporites and precipitates.

• Evaporite- sedimentary rocks formed by the evaporation of water.

• Precipitate- forms when water is so full of a dissolved mineral that the mineral no longer dissolves and crystallizes in the water.

• Examples:

• Rocks salt

• Rock Gypsum

• Dolostone

Rock Salt

Dolostone

Organic Sedimentary Rocks

• Also known as bioclastic or biochemical sedimentary rocks.

• Organic Rocks- Made from compacted organic matter (things that were once living)

• The only rock that contains fossils or evidence of life.

• Depending on the grain size, an organic sedimentary rock can be chemical or clastic.

• Examples:

• Coal

• Biochemical Limestone

• Fossils

Biochemical Limestone

Coal

Fossil

Sedimentary Rock Textures

• How does the rock feel?

• Clastic Sedimentary Rocks

• You can see the grains with your eyes or with

a magnifying glass.

• If you rub the rock, dust particles are left on

your hand.

• Chemical Sedimentary Rocks

• If it looks smooth like plastic or if you can

see a crystal structure.

Sedimentary Rock Composition

• What is the rock made of?

• Organic

• If the rock contains a fossil, shells, or any other signs of former life, the rock is bioclastic/organic.

• Inorganic

• If the rock does not have any signs of life, then it only contains minerals.

Classifying Sedimentary Rocks

• Identify the rock’s:

• Texture

• Composition

• Texture + Composition= rock name

• Once the rock is identified, you can

use it to learn about a region’s past.

Why Study Sedimentary Rocks?

• Sedimentary rocks are a great way to

examine an area’s past.

• The rock material and fossils present

can help you make conclusions about

how the environment used to be in a

given area.

• Example:

• Based on evidence from sedimentary

rocks, scientists were able to discover

that Death Valley used to be a lake.

Watch This and Fill Out Your Graphic

Organizer

https://www.youtube.com/watch?v=Etu9BWbuDlY