Sedimentary Rocks

Sandstone

What Is A Sedimentary Rock?

• Formed from sediments (rock fragments, mineral grains, animal & plant remains-shells, bones, leaves, stems) that are pressed or cemented together or when sediments precipitate out of a solution.

Halite (Salt)

• These sediments are moved by wind, water, ice or gravity then deposited into layers.

• Sedimentary rocks represent 7% of the Earth’s crust, but they cover 70% of the Earth’s surface.

• Sedimentary rocks are fossil-carrying rocks.

What turns sediments into solid rock?

• Water or wind breaks down and deposits sediment (erosion & deposition)

• Elements of Erosion are heat, cold, rain, waves, and grinding ice.

• At first sediments fit together loosely, over long periods of time, thick layers build up. Because of the heavy layers, the upper layers press down on the layers below them, causing Compaction

• Dissolved minerals flow between the particles and cement them together (cementation)

3 Types of Sedimentary Rocks:

• Clastic —made of broken pieces of other rocks. Formed when rock fragments are squeezed together.

Shale

• Formed from tiny particles of clay compacted together.

Sandstone

• Forms from the compaction and cementation of small particles of sand.

Conglomerate and Breccia

• Conglomerate: Formed from fragments of various sizes of rocks and pebbles. Fragments are rounded because they have been worn along riverbeds.

• Breccia: Fragments are jagged with sharp edges. Formed from various size of rocks and pebbles.

Organic Sedimentary Rocks

Organic—remains of plants and animals are deposited in thick layers

• Organic refers to substances that once were part of living things or were made by living things which contain calcite or calcium carbonate. (Can be tested by using acid)

Organic Sedimentary Rocks

• Coal: Remains of swamp plants buried in water or by volcanic ash.

• Limestone: Formed by hard shells of once living things such as coral, clams, oysters, and snails. When they die their shells pile up and are covered by other sediments compacting and cementing them

• Chalk-can be naturally occurring and in rock form.

• Coquina-made of large fragments of shells.

Chemical Sedimentary Rocks

• Chemical—minerals dissolved in lakes, seas, or underground water. Can occur when lakes evaporate

Chemical Sedimentary Rocks

• Rock Salt: Made of the mineral halite.

• Gypsum: Formed by evaporation in dry climates