Presentation on theme: "Weathering Soils Mass Movement Chapter 8. TOPIC 1 Weathering- The break-up of rock due to exposure to the atmosphere. Depth of rock a factor. –GRANITE."— Presentation transcript:
TOPIC 1 Weathering- The break-up of rock due to exposure to the atmosphere. Depth of rock a factor. –GRANITE - Formed deep in Earth Factors on rock - Rain, wind, gravity, Erosion - Agents also include glaciers, waves, currents.
Weathering Types Mechanical –Break or split; –No composition change “Disintegration” Chemical –Water & water Vapor important agents. –Substances changed “Decomposition”
Mechanical Weathering Frost Action - Wetting & Drying - Plant/Animal Actions- Overlying rock layer loss
Frost Action - –Water takes up 10% more space when frozen. –“Frozen Pop” –“Ice Wedging” - Northern United States Occurs in porous rocks. Bare mountain tops (FIGURE 8.1) –Potholes (roads) Ice Heaving Mechanical Weathering
Wetting & Drying –Break up rocks that contain CLAY –Swelling & Shrinking –Shale an example
Mechanical Weathering Plants/Animal Actions –Lichens - Figure 8.2 Roots wedge cracks apart –Digging Animals Holes allow access for water to erode bedrock
Mechanical Weathering Rock Layer Loss Exfoliation –(Figure 8.3)
Chemical Weathering Hydrolysis- Minerals unite with water –CLAY a product of hydrolysis. Oxidation - Oxygen and other substances Chemically Combine. Carbonic Acid- CO 2 dissolved in water –Erodes Calcite –Limestone Caverns –Gypsum & Halite are eroded by this too.
Weathering Rate Rock Types Climate where rock is located. –Wet Climates –Dry Climates –Variable Climates
Earth Matters Acid Weathering Marble statues Increased rusting & corrosion Why would National Park Service people be interested in studying the effects of Acid rain?
Weathering Results Soil Formation Sand, Clay, Silt known ingredients Parent Material Residual Soil - bedrock as parent material. Transported soils- Caused by what?
SOIL PROFILE A, B, C, Bedrock layer. Horizons Topsoil - “A Horizon” –Gray to black in color –Humus from decaying of plants B Horizon - Clay is washed to this level –Red / Brown from iron oxides C Horizon - Rock fragments
Factors on Soil Climate –Mature soils in Wet Tropical places similar. –Tropical Soil - Formed in constant high temp. and heavy rainfall. Chemical weathering faster. –Grassland Soil - Profile > 1 meter thick Very Fertile due to Organic material. Figure 8.12
Factors On Soil –Forest Soils - Cool season, hardwoods / evergreens. NOT very fertile. –Desert Soil - Profile seldom over 3cm. CALCIUM RICH. Fertile when watered!!! –Arctic Soils - High elevations/latitudes, boggy, PermaFrost
Mass Movement Steep slopes weathering > gentle slopes Creep - Noticed by its effects. Fence posts Talus - Rock slope at cliff base. 40 deg.or < Avalanche - Landslide of rock, snow, soil. Slumps - Cliffs, steep hills, roadsides –Collbran area Mudflow - Water saturated Clay & Silt
Soil Conservation Windbreaks Contour Farming Strip Cropping Figure 8.15 page 143 No-till - All processes done at once