Sedimentary Rocks & Weathering Notes
Sedimentary Rocks • Formed from weathering, erosion and deposition of existing rocks.
Weathering & The Creation of sediments Begin with a parent rock of any type and then go through: 1. Weathering – physically or chemically breaking the rock down into small fragments 2. Erosion – moves sediment from one place to another place 3. Deposition – sediment settles in a new location. You now have a sediment!
Compaction and Cementation Sedimentary Rocks can form from compaction and/or cementation. • Compaction – adding pressure to squeeze particles together. • Cementation – “gluing” together of sediments from water solutions.
Sediments…. • Are deposited in layers and compacted & cemented to make a sedimentary rock • Often have a “layered” look • Stratification – the process by which sedimentary rocks are arranged in layers • Often record ripple marks, mud crack, and fossil
What is Weathering • The process that breaks down rocks and other substances at Earth’s surface. Heat, cold, water and ice all contribute to weathering. • Two Types of Weathering: Chemical Weathering Mechanical/Physical Weather • Mechanical Weathering Mechanical weathering breaks rock s into pieces by freezing and thawing, release of pressure, growth of plants, actions of animals, and abrasion
Organic Activity • ROOTS of trees and other plants enter cracks in rocks. As the roots grow, they force the cracks apart. Overtime the roots of even small plants pry apart cracked rocks. • Insects, earthworms, and burrowing animals often disrupt soil layers, exposing parts of bedrock to weathering .
Gravity… • The force that moves rock and other material downhill. • Gravity causes mass movement, any one of several processes that moves sediment downhill.
- Spring '09
- clastic sedimentary rocks, Example