GEOG 1011 Midterm 2 Study Guide

GEOG 1011 Midterm 2 Study Guide - Midterm 2 Study guide...

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Midterm 2 Study guide Geog 1011, Landscapes and Water Fall 2007 Don't forget: some questions will come from lab exercises (Azimuth, aspect, gradient and profile; soils field trip; soils internet lab), homework #2 (see answer key- it will be posted soon), the landslides video (shown in class on 10/15) and Susan Riggins' lecture on regolith (10/17) What is the critical zone, and what layers comprise the critical zone? Weathering processes are responsible for creating an environment at the Earth’s surface that can be thought of as a porous membrane where air, rock, water and life interact. The Critical Zone is where the atmosphere, biosphere, hydrosphere and lithosphere intersect, and includes everything from unweathered rock to the top of the vegetation canopy. It is within the Critical Zone that soils (the pedospher) form. The layers in the weathered profile are: 1. Soil: disaggregated and altered rock material mixed with organic matter. 2. Regolith: disaggregated rock. The regolith layer includes soil (if it is present). 3. Weathered rock: this is rock that is fractured and/or chemically altered, but has not been moved by transport processes. What does chemical weathering do; what does physical weathering do? Physical weathering processes break rock down by fracturing it. Breaking rock affects its properties by: 1. Producing smaller chunks that are then transportable by available processes. 2. Creating avenues for water to infiltrate and move through the rock. 3. Producing surface area. Chemical weathering is the chemical alterations of minerals and rocks at Earth surface conditions. It happens because many minerals are chemically unstable at conditions at the Earth's surface. Chemical weathering processes involve interaction of water and minerals at the surface of the mineral. Just as coarse rock salt dissolves more slowly than finely ground salt, big rock chunks weather more slowly than finely divided rock. Soils are typically made of very small particles indeed- sand and silt and clay- and the surface area of a small quantity of soil consequently can be very large. Why is the amount of surface area produced important? Crushed rock increases the chemically reactive area and the space for microbial habitat. In addition to being a surface for chemical processes to operate on, these surfaces provide habitat for a variety of bacteria, fungi and other small living things. Physical weathering processes- Tectonic crushing: Where the crust is deformed by tectonic processes, it is pervasively fractured by earthquakes at depths well below the surface. The rock is
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already fracture riven when it enters the critical zone—effectively preconditioned for weathering. Exfoliation jointing:
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GEOG 1011 Midterm 2 Study Guide - Midterm 2 Study guide...

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