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 - 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?

Soil Conservation Topic II

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