Weathering The effects of the physical and chemical environment on the decomposition of rocks - Igneous rocks form at high temperatures and the constituent minerals reflect the conditions of formation. The minerals are not necessarily stable at surface conditions, long after they cooled. - Weathering can be thought of as an attempt by rocks to attain physical and chemical equilibrium with the surface environment. - Most igneous minerals are not stable on Earth’s surface. Given time most will decompose. Addition of extra energy (heat or mechanical energy) reactions will proceed sooner, rather than later
48
Embed
Weathering - SOEST › GG › FACULTY › KJOHNSON › GG103 › lecture…Weathering The effects of the physical and chemical environment on the decomposition of rocks - Igneous rocks
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Weathering
The effects of the physical and chemical environment on the
decomposition of rocks
- Igneous rocks form at high temperatures and
the constituent minerals reflect the conditions
of formation. The minerals are not
necessarily stable at surface conditions, long
after they cooled.
- Weathering can be thought of as an attempt
by rocks to attain physical and chemical
equilibrium with the surface environment.
- Most igneous minerals are not stable on
Earth’s surface. Given time most will
decompose. Addition of extra energy (heat or
mechanical energy) reactions will proceed
sooner, rather than later
Chemical and Physical Weathering
Factors that affect the efficiency of
physical weathering
1. Topography and relief
e.g., falling down hill; pounding by
waves
2. Climate
Especially temperature, and diurnal
variations
3. Original structure
Porosity and permeability are
especially important
Hot and wet is hardest on rocks
Lahaina Cliffs Trail, W. Maui
Factors involved in Chemical Weathering
1. Original Composition
- Some substances are more resistant to alteration than others.
- In Hawai‘i, glass and olivine are the least stable substances
2. Physical Environment (see above)
3. Chemical and Biological Environment
- Microbial activity is important in all weathering processes
- Most rain water and ground water in Hawai‘i is acidic