Lecture 10: Weathering Flashcards
What is Mechanical Weathering?
The physical break up of rocks composition
What are the 3 ways Mechanical weathering occurs?
- Intrusive rocks cool and form joints which
- Exfoliation where large sheets of rock are detached from outcrop
- Frost wedging when ice expands and wedges rocks
What is the Principal effect of Mechanical weathering?
Breaking up large chunks of rock into smaller ones and increasing surface are
What is Glaciation?
A way that bedrock is eroded and broken down into much finer particles
What are the particles produced by glaciation known as?
- Till - Large particles
* Glacial flour - Fine particles
What is Chemical weathering?
The breakdown of minerals by chemical reaction with water or gases
What does Chemical weathering depend on?
- Parent material
* Climate
Which Parent materials are the least stable in chemical weathering?
High temperature formed minerals are least stable
What are the least stable minerals in terms of chemical weathering?
Halite
Calcite
Olivine
Calcium rich plagioclase
Why are Halite and Calcite the least stable?
Because they form under evaporative conditions and salt dissolves quickly
Why are Olivine and Calcium-rich plagioclase less stable?
Because they crystalize out of magma at high temperatures
What are the most stable minerals in terms of chemical weathering?
Iron oxides
Aluminum
Quartz
Why are clay minerals stable?
Because they form out of the melt at the lowest temperatures
Why are Quartz and Muscovite mica stable?
Because they form out of the melt at the lowest temperature
Why are iron oxides and aluminium hydroxides the most stable?
Because they form during soil formation
How does CO2 get removed from the atmosphere?
Water react with carbon dioxide to form carbonic acid
The carbonic acid ionized to form bicarbonate ions which react with rocks weathering it
What occurs in redox reactions?
Minerals that reduced elements in them react with oxygen
What is the Regolith?
The loose soil that sits on top of the bedrock
How does Climate affect the rate of chemical weathering?
The warmer and wetter the climate the more chemical weathering can occur
The colder and dryer the climate the less chemical weathering can occur
What are the two types of Biological weathering?
Mechanical and Chemical
What occurs in Biological chemical weathering?
Actions of the tree roots split the rocks apart
What occurs in Biological chemical weathering?
Organic acids are produced through decaying vegetation
What does Aerobic respiration of dead organic matter lead to?
The formation of carbon dioxide and water
What occurs when carbon dioxide and water mix?
They farm carbonic acid which dissociates to form bicarbonate and protons
