What do: Grand Canyon

Chalk

White Cliffs of Dover

Sidewalks

All have in common?

Grand Canyon

SEDIMENTARY ROCKS

• Sedimentary rocks

form from various types

of sediment.

• Sedimentary rocks make up 90% of SURFACE rocks and only about 1% of Earth’s crust.

SEDIMENTARY ROCKS

• Which rock is it that makes up Earth’s continental crust? ________________

• Which rock is it that makes up Earth’s oceanic crust? _____________________

• Both of those are Igneous rocks.

Granite

Basalt

Three Kinds of Sedimentary Rocks

• 1. Clastic – fragments of other rocks. For example: shale, sandstone, conglomerate

• 2. Crystalline – formed from mineral grains that fall out of solution by chemical action or evaporation. For example: Rock salt and chemical limestone.

• 3. Bioclastic – formed from remains of plants or animals. For example: Coal and limestone from shells (coquina).

How are Clastic Sedimentary Rocks formed

• Sediment is deposited and then goes through the process of lithification (forming sediment into sedimentary rocks)

How are Clastic Sedimentary Rocks formed

Weathering

Erosion/Transport

Deposition

Lithification

Clastic Sedimentary Rocks

• Clastic sedimentary rocks are characterized based on their grain size.

How are Clastic Sedimentary Rocks formed.

• Grain sizes vary from Coarse (pebbles, cobbles, boulders) to Medium (sand) to Fine (silt and clay).

Grain SizesGrain Sizes

BouldersBoulders

CobblesCobbles

Coarse GravelCoarse Gravel

Fine GravelFine Gravel

Coarse / Medium SandCoarse / Medium Sand

Fine Sand – Powdered SugarFine Sand – Powdered SugarSilt - PowderSilt - Powder

Mixed

How Does The Sediment Get Sorted Into Different Sizes?

• Running water (rivers, streams, creeks) pick up sediment and carry it along its travels.

• The faster the water is moving, the larger the particle that can be carried, and vice-versa.

• When a river hits a larger body of water, like a lake or ocean, it’s like hitting a brick wall. This results in the river “dumping it’s load” – dropping all the sediment it’s been carrying.

• The sediment gets dumped according to size!!

How Does The Sediment Get Sorted Into Different Sizes?

• The bigger sediment gets deposited FIRST, since it’s bigger, heavier and sinks first.

• Then, the sediment gets gradually SMALLER the farther you go from where the river hits the lake or ocean.

• Therefore, coarse clastic rocks get made where the larger sediment gets deposited and the medium to fine clastic rocks get made further away from that point.

Clastic Sedimentary Rocks

Conglomerate – made of pebbles and/or cobbles cemented together by sand, silt and clay. Coarse-grained

Sandstone – sand that has been cemented together. Medium-grained

Shale – made from clay. Fine-grained

Crystalline Sedimentary Rocks

• Also called chemical sedimentary rocks.

• Chemical action or evaporation causes minerals to drop out of solution.

• This process creates chemical or crystalline sedimentary rocks.

• For example: Calcite will precipitate out of water and build-up to form chemical limestone (it will fizz with acid since it has calcite in it!!!)

Crystalline (Chemical) Sedimentary Rocks

Gypsum Rock – made when the mineral gypsum precipitates out of water.

Chemical Limestone

What happens when salty water evaporates and just salt is left

behind?

Bonneville Salt Flats of the Great Salt Lake, Utah. The lake bed is covered with rock salt which gives it the white color. The salt is mined by the Morton Salt Company.

Bioclastic (Organic) Sedimentary Rocks

• Also called Organic sedimentary rocks.

• Formed from once-living things like plants and animals.

• For example: Plants die and decay and form coal.

• Another example: Shells can get broken up and cemented back together to form organic limestone (also called coquina).

Bioclastic (Organic) Sedimentary Rocks

CoalOrganic Limestone or Coquina

Bioclastic Rock