| This film shows a summary of weathering processes at the Earth's surface,
its role in the formation of soils and the relevance of soil in the maintenance
of terrestrial life. Make sure you know the differences between mechanical
and chemical weathering and how these two different forms of weathering
work together. The various factors that influence mechanical and chemical
weathering are analyzed. Although weathering is a natural process, human
activities can accelerate it to the detriment of living creatures. The
formation of soil is a consequence of weathering. The importance of soil
for the terrestrial food chain is described in the rest of the film as
well as the way in which human activities disrupt natural processes and
cause erosion. The final part focusses on a case story, emphasizing the
agents of erosion and the strategies to mitigate the problems.
Questions to complete while watching the film during the class: 1. Not all the rocks that appear at the surface are formed at the surface. After uplift from their environment of formation, rocks are changed into a form that is ____________________ under the new conditions at the Earth's surface. 2. The break down of a rock into fragments or even into its mineral components by physical processes is called _______________________________________. 3. Granites often develop joints (fractures) oriented parallel to the ground surface because, at the surface, they are no longer under the high pressure where they formed. Plates of granite peel off the surface of the outcrop, layer by layer, like the stripping of skins from an onion, in a process known as _________________________________. This is an example of _______________________ weathering. 4. Does mechanical weathering result in a change in the bulk chemical
composition of the parent rock? Why?
5. What are the principal agents of chemical weathering? ________________________________. 6. By breaking rocks in smaller pieces, mechanical weathering ________________________ the amount of exposed surface. This will ________________________ the action of chemical weathering. 7. As rainwater percolates through decaying vegetation and soil, it
picks up __________________
8. Does chemical weathering change the bulk chemical composition of
the parent rock? Example.
9. In very wet, tropical climates, ________________________ is the dominant form of weathering, enhanced by the abundance of water and the high ____________________. 10. In dry climates, __________________________ weathering is the dominant form of weathering. 11. What mineral is very stable at the Earth's surface? _____________________________ 12. The minerals most unstable and that weather the fastest at the Earth's surface are those that form at the _________________ temperatures. (Hey, remember Bowen's series for this!) 13. The billions of tons of CO2, nitrogen oxides and SO2 added every year from the burning of fossil fuels and forests combine chemically with rain water creating solutions many times more acidic than natural rain. The effect of this kind of precipitation creates a global environmental problem known as ________________________. 14. The most important source of acid rain is the SO2 emitted by automobiles and from industries and power plants burning high sulfur ____________. 15. Soil is the foundation upon which the entire __________________________ depends. 16. The A-horizon is the loamy ______________________ found at the surface. 17. Rain water seeps down through the A-horizon and leaches away some of the soil material down to the B horizon, the next layer where the leached material are ____________________. 18. The C- horizon, the bottom-most layer, is the zone where the are still fragments of the ______________________________ scattered among the weathered material. 19. Granite weathers into a sandy soil made up of _________________________ grains. Clay in the soil comes from the weathering of _______________ 20. Basalt decomposes more rapidly to _____________________ minerals and iron compounds. 21. The floor of a tropical rainforest is actually a rather _________________ soil. Most of the nutrient in the rainfores is provided by the organic matter from the forest itself when it decays. When the rainforest is cut down, the humus is exposed to ______________________. 22. A combination of factors produced the famous Dust Bowl of the 1930's. |