 Objectives:  1. Identify the kinds of materials that make up sedimentary rocks.  2. Describe three groups of sedimentary rocks  3. Explain how sedimentary rocks record past conditions.

 Sedimentary rocks form from loose materials that get pressed together or cemented into rock  Sediments are materials that settle out of water or air.  Sediments can be made up of loose pieces of rocks, minerals, plant and animal remains.  Most transported sediment settles out of a fluid  Ends up being deposited in rivers, lakes and most of all in the oceans.

Sedimentary Rock Formation There are two processes that can change sediments into rocks. 1. Compaction – one layer gets buried by another, and then another. The overlying layers press down on the sediments underneath 2. Cementation – The sediments are held together by minerals that have crystallized between them, acting as a cement. Common Sedimentary Rocks: Sandstone, Limestone, Conglomerate, Shale, Chert, Rock Salt

Sedimentary Rocks ChertConglomerate Limestone Rock Salt SandstoneShale

Cementation

Coal Coal is made up of the remains of plants – dead wood, bark, leaves, stems, and roots Coal is an unusual sedimentary rock because it forms from plants instead of earlier rocks. The coal we use today started forming millions of years ago in swamps.

Sedimentary Rocks and Past Conditions SSedimentary rocks are laid down in layers with the oldest layer on the bottom. SSedimentary rocks can tell scientists what the conditions may have been like in the past FFossils of fish or shells can show that the area was once covered by water SSedimentary rocks can also show that an area was flooded. MMud cracks show that rocks formed in areas where wet periods were followed by dry periods.