Chapter 3 – 3 Sedimentary Rocks

How do sedimentary rocks form?

Sandstone is the most common form of sedimentary rock. Arches Park!

Sediment – small solid pieces of material from rocks or living things.

Erosion helps to create sediment. Water or wind loosens and carries away fragments

of rock.

Deposition re-deposits sediment at the bottom of a lake or ocean where it

compacts and cements and changes to sedimentary rock!

Compaction is that process that presses sediments together. Year after year, the weight

of the layers becomes greater and greater.

Cementation is the process in which dissolved minerals crystallize and glue particles of the sediment together into

sedimentary rock.

Types of Sedimentary Rocks include Clastic and Organic Rocks.

Clastic rock forms when rock fragments are squeezed together. From tiny microscopic

particles to huge boulders.

Shale is formed from tiny particles of clay. No cementation is needed to hold shale together.

Sandstone is a clastic rock that forms from the sand on beaches, riverbeds and sand

dunes.

Compaction and cementation of quartz material often leaves spaces for water to

seep in.

Conglomerate and Breccia are sedimentary rocks containing a mixture of rock

fragments of different sizes.

Conglomerate rocks have fragments of rock stuck in that have rounded edges.

Breccia are sedimentary rocks that contain large fragments with sharp edges.

Organic rock forms where the remains of plants and animals are deposited in thick layers. Coal & Limestone.

Coal forms from the remains of layers and layers of swamp plants. Buried for millions

of years, they slowly change to coal.

Limestone includes the remains of marine life. Coral, clams, oyster and snail shells contain

calcite, a mineral that with pressure and over time, forms limestone.

Chalk is a very common form of limestone. Chalk is made from the skeletons of living

things.

Chemical rocks form in nature when minerals dissolved in solution crystalize.

Dry lake beds often have deposits of halite (salt), gypsum & tufa.

Uses of sedimentary rock include building materials, cement, and iron ore

production.