Sedimentary Rocks as the name suggests, form from sediments, usually deposited in horizontal layers as seen here

What is a SEDIMENT? 1) Solid particles, such as weathered rock fragments, plants or animal remains: sand, clay, pebbles, shells, etc. small pieces of broken down rocks = clasts 2) Minerals that settle out of solution onto lake and ocean bottoms, such as rock salt, dolostone, gypsum

But in order for the sediments to become hard rock, the particles in the sediment must be permanently cemented together as seen in this sandstone Compaction and cementation must both happen for sedimentary rock to form. Minerals like quartz and calcite often serve as the cement

River entering an ocean Pressure compacts The sediments

A conglomerate is formed in a beach environment and is composed of larger rock sediments from various origins

Conglomerate boulder

Sedimentary rocks made of sediment grains (clasts) are called CLASTIC SEDIMENTARY ROCKS Sandstone, shale, conglomerate, and breccia are all clastic sedimentary rocks

Sedimentary rocks like this shale often contain fossils

Great Salt Lake in Utah contains many minerals dissolved in it

If it were to evaporate away, it would leave behind those minerals in the form of rock salt, and rock gypsum. Rocks that form in this way are called evaporites. They are crystalline.

Limestone and Dolostone can precipitate from seawater that is warm and shallow

The chalk cliffs of Dover are composed of a limestone containing microscopic shells

Sedimentary rocks that are made up mostly of life forms, like shells or plant remains, are called BIOCLASTIC Limestone and coal are bioclastic rocks

Larger shells are often found in limestone

Millions of years ago lush fern forests dominated the land

As these ferns died, their remains piled up in large bogs. In many places the decaying plant remains became thousand of feet thick

After millions of years and under great pressure, coal is the rock that forms from the remains of these plants

Fern fossils are often seen on pieces of coal

How can you tell if a rock is SEDIMENTARY? Look for pieces of other rocks (sand grains, pebbles, etc.) Does it feel like sandpaper? (sand sized pieces) Does it feel “dusty” (silt sized pieces) Does if feel “smooth” (clay or mud) Look for horizontal layering of the sediments Look for a fossil Does it react with acid (Limestone)? Look for other sed. features (mud cracks, cross bedding etc.)