Sedimentary Rock Notes
Weathering= rocks and sediments break down
Erosion= smaller pieces are moved to new locations
Three types:
1) Physical (mechanical)
2) Chemical
3) Biological
What is physical weathering?
· NO changes in composition
· size and shape change
· Factors:
Temperature
__Frost Wedging__________: water freezes and expands, cracking rocks
Pressure
__Exfoliation__________________: pressure of overlying rocks are removed, underlying rocks can expand
What is chemical weathering?
· Mineral composition _Changes_________________
· Chemical reaction occurs __________________
· NEW minerals form agents__________________
· Agents:
¡ Water- Hydrolysis
¡ Oxygen -Oxidation's
¡ Carbon Dioxide- ex: cave
¡ Acid ex: acid rain
Why is biological weathering?
· Living organism cause changes in rocks or sediment
· Ex: Tree roots growing around a rock and splitting it
· Ex: Humans displacing or removing rock surfaces
Factors that affect weathering:
Climate for chemical weathering: is more common/faster in areas of warm temperatures and high rainfall
Example: “painted desert” of Arizona/New Mexico
Climate for physical weathering: is more common/faster in areas of cool/dry climate
Example: NC Mountains
Formation of Sedimentary Rocks
Even though igneous rocks are the most common in Earth’s crust, most of Earth’s surface is covered in sediment.
Sediments: Pieces of solid rock material re-deposited on Earth’s surface by forces (wind, water, ice, gravity, precipitation, etc.)
Steps:
1) Weathered particles get moved downhill: ____erosion__________________
2) Get laid down/sink: ____deposition______________
3) Deposits become layered: _sorting_________________
4) Layers stack up on top of each other: ______burial____________
5) These processes add material to _________sedimentary basins____________________
6) As burial occurs, layers are subjected to greater ___heat and pressure___________________________
7) These conditions cause ___lithification__________________
· lithos = stone
· sediments- sedimentary rocks
· Two steps:
· Compaction: excess water and air are squeezed out
· Cementation: new minerals form
The primary features of sedimentary rocks are horizontal layers called bedding.
- Graded bedding
- Bigger on the bottom
- Cross-bedding
- Slanted layers
Sedimentary Rock Classification
Organic sedimentary rocks: form from one living things
Chemical sedimentary rocks: evaporates
Clastic sedimentary rocks: loose deposits on Earth`s surface (most common)
- Bigger on the bottom
- Slanted layers
The Physical Properties
|
Polymorphic and Polymorphs |
Important Physical properties
CleavageOrientation and number of planes of weakness within minereal
Fracture descrbes how minerals break if it is not along well defined planes
Fracture descrbes how minerals break if it is not along well defined planes