Assignment# 10 Sedimentary Rocks How do they form?

SEDIMENTARY ROCKS SEDIMENTARY ROCKS WILL CONTAIN FOSSILS. There are 2 ways sedimentary rocks are formed 1. Clastic are made from sediments glued together 2. Non-clastic: not glued together---include chemical & biochemical/organic SEDIMENTARY ROCKS WILL CONTAIN FOSSILS.

Oldest rocks are on the bottom….youngest on top SEDIMENTARY ROCKS FORM IN LAYERS CALLED STRATA Oldest rocks are on the bottom….youngest on top

This is a good example of Stratification

THE 2 CLASSES OF SEDIMENTARY ROCKS 1. CLASTIC Sedimentary Rocks are made from sediments that come from pre-existing rocks that have been weathered (breaking down into smaller pieces) and eroded (transported away) then glued together. The 2 types of weathering include physical (only size changes) and chemical (a new substance is formed).

Sediments range in size from tiny pieces of clay to sand, to pebbles, and to stuff as big as boulders Clastic rocks form in a process called lithificaton which means compaction and cementation are occurring

Layers of sediment are deposited at the bottom of oceans and lakes Here’s How They Form: Layers of sediment are deposited at the bottom of oceans and lakes As the layers build one on top of another, the pressure on the bottom layers COMPACTS the sediments together In the empty spaces between sediments, natural glues, like calcite, CEMENT the sediments together Demo of Sedimentator

Look at the processes that are occurring in this animation

Clastic Process

Examples of clastic sedimentary rocks include CONGLOMERATE BRECCIA SHALE SANDSTONE

Non-Clastic contain 2 types: chemical and biochemical CHEMICAL Sedimentary Rocks are made from mineral crystals that formed from chemicals dissolved in water. Here’s How They Form: The water in the oceans, lakes, and underground is often full of dissolved minerals like halite and calcite. Water evaporates leaving the solids behind: rock salt is formed when salt is left after evaporation and limestone is formed when calcite is left behind

Chemical Sedimentary Rocks are also formed in caves where mineral-rich water drips from the ceiling, creating stalactites and stalagmites made out of limestone Limestone Limestone Cave Examples of chemical sedimentary rocks include limestone and rock salt

will be found near areas of lots of biological activity BIOCHEMICAL OR ORGANIC Sedimentary Rocks are made from remains of once-living plants or animals (organic matter) will be found near areas of lots of biological activity this is the sedimentary rock type with the most fossils Biochemical sedimentary rocks include: coquina, chalk, coal and limestone CHALK Made from dead animals COAL Made from dead plants COQUINA Made from shells LIMESTONE with fossils in it