Warm Up In your journal, please title a page Sedimentary Rocks and draw five of the following identification cards Other important facts: Rock name: Color: Streak: Sediments: Group: Sketch

Sedimentary Video

II - Sedimentary Rocks layered rocks Seventy-five percent of surface rocks are sedimentary. Types of sediments that make up these rocks: Mud/clay—smallest grain Silt—next smallest grain Sand—small grain Gravel—greater than 1 mm up to pebbles and boulders Shells/bones from sea creatures (these settle on the ocean floor) Evaporites (mineral deposits)

Movement of sediments is by wind or water The faster wind/water goes, the larger the sediment it carries. The larger sediments are deposited first and the smallest last. Over millions of years, mud, sand, gravel, bones and shells settle to the sea floor as sediments. Layers pile up many hundreds of meters thick. Lower layers are pressed together more and more tightly under the weight.

Major Characteristics: Compaction—pressure on lower sediments changes them into rocks Cementation—some sediments are joined together or cemented by minerals dissolved in water Strata—result of these processes is the formation of layers of sedimentary rock

Sedimentary rocks are usually formed in the water. These rocks are the only rock in which fossils are found (fossils are remains or traces of past plants and animals that are preserved). They are grouped according to composition and grain-size (texture).

Groups: Clastic rocks Organic rocks Chemical rocks

Clastic rocks formed from broken pieces or fragments of rocks, classified according to size and shape of fragments. Conglomerates—made of rock particles of different sizes, sand and mud. Found where rivers slow and where waves break apart rock. Pieces are rounded by water. Sandstone—small sand-sized grains cemented together by minerals. Shale—forms in quiet waters—swamps and bogs. Made when particles of clay and mud get pressed together. Siltstone—similar to sandstone but has much smaller grains and contains large quantities of clay.

Organic rocks formed either directly or indirectly from material that was once living. Limestone—made of calcite (shells of clams, oysters). Coquina—an example of limestone with large shell fragments. Chalk—type of limestone composed of small pieces of animal shells (make up the cliffs of Dover) Coal—made from plants that died millions of years ago.

Chemical rocks formed by chemical means that do not involve living organisms. Formed from deposits of fluid. Rock salt—made from the mineral halite Gypsum—made from the mineral gypsum.