Geology 101 - Lecture 11
Weathering and Erosion
(Brief Outline Only)
Weathering, erosion, transportation, deposition, lithification
- weathering - decomposition and disintegration of rocks at the surface
- erosion - the incorporation and transportation of material by mobile agents such as water, wind, or ice
All rocks at the surface will weather and erode whether they are igneous, metamorphic, or sedimentary
A. Types of weathering
- Mechanical Weathering - physical disintegration of rock
- frost wedging
- unloading
- thermal expansion
- biological activity
- Chemical Weathering - rock chemically decomposes
Agents are water, CO2, and oxygen (solution, oxidation, hydrolysis
B. Rates of weathering
Depends on:
- Rock type - granite or limestone
- Climate - humid vs. arid
C. Products of weathering
-
Clastic particles (sediment) - solid particles from mechanical weathering
Classification depends on size: boulder, cobble, pebble, sand, silt, clay
. Accumulations of these products called clastic or
detrital sediments
- Dissolved particles - ions or molecules dissolved in water.
These dissolved materials can be precipitated from water and
accumulate as chemical and biochemical sediments)
- Soil - loose, unconsolidated, uneroded sediment material
Product of centuries of mechanical and chemical weathering of rock plus addition of organic material
II. Classification of
Sediment and Sedimentary Rocks (see Table 6.1)
III. Lithification
- A. Compaction
- B. Cementation