Sedimentary Rocks

Sediments Pieces of solid material that have been deposited on Earth’s surface by wind, water, ice, gravity, or chemical precipitation.

Weathering A set of physical and chemical processes that break down rocks into smaller pieces (sediments). Physical Weathering: The minerals remain chemically unchanged, rock fragments simply break off. Chemical Weathering: Occurs when the minerals in a rock are dissolved or otherwise chemically changed.

Physical Weathering

Chemical Weathering

Weathering Cont… Weathering produces rock fragments know as clastic sediments, which can range in size from huge boulders to microscopic particles. They usually have worn surfaces and rounded edges caused by physical abrasion during erosion and transport.

Some Cool Pictures of What Weathering Can Do

What are the four main agents of erosion? Erosion: The removal and movement of surface material from one location to another What are the four main agents of erosion? wind moving water gravity glaciers

Erosion In Action

Deposition When sediments are laid down on the ground, or sink to the bottom of bodies of water.

Lithification The physical and chemical processes that transform sediments into sedimentary rocks. Lithification begins with compaction . As temperature begins to increase with depth, sediments begin to experience chemical and mineral changes that cause cementation.

The two types of Cementation * when a new mineral, such as calcite or iron oxide, grows between the sediment grains * when existing mineral grains grow larger (this can happen if heat is introduced, or when more of the same mineral precipitates out of the groundwater)

Evidence of past life is visible in sedimentary rocks as fossils.

Types of Sedimentary Rocks Clastic Sedimentary Rocks: The most common type of sedimentary rock. Formed from the abundant deposits of loose sediments found on Earth’s surface (and can be further classified by the size of their grains) Coarse-Grained: gravel-sized rock and mineral fragments Medium-Grained: sand-sized rock and mineral fragments Fine-Grained: sedimentary rocks consisting of silt or mud (logically called siltstone or mudstone)

Chemical Sedimentary Rocks sediments that form from the evaporation of mineral-rich water (called “evaporites”). The “chemical” sediments can then go through the process of compaction and cementation

Organic Sedimentary Rocks Sediments that are formed from the remains of once-living things. These too, can then go through the process of compaction and cementation

Sedimentary Rocks in N. America