- older rocks are usually found at the bottom layers, however, sometimes forces within Earth overturn layers of rock, and the oldest are no longer at the bottom.
- sedimentary rocks are usually classified as detrital, chemical or organic. <ul><li>detrital = clastic </li></ul><ul><li>chemical and organic = nonclastic </li></ul><ul><li>* you need to know all of these terms!!! </li></ul>
- Detrital sedimentary rocks: made from broken fragments of other rocks
1. when rock is exposed to air, water, or ice, it is unstable and breaks down. This process, which breaks rocks into smaller pieces, is called weathering.
2. when layers of small sediments stick together because of pressure, compaction occurs.
3. when water and other minerals (such as quartz, calcite and hematite, which act as naturally glues) move through open spaces between larger sediments, gluing them together, cementation occurs.
4. Detrital rocks have granular textures, much like granulated sugar. They are named according to the shapes and sizes of the sediments that form them. Breccia: angular Conglomerate: rounded