SOILS • Most important result of weathering and Erosion is soil • Soils - soil science = PEDOLOGY • Residual soil - soil made from local bedrock (weathered material) • Transport soil - soil that was moved by wind, water, ice, or gravity (weathered and eroded material)
SOIL • Factors determining soil makeup • 1. Climate - Rainfall amount and temperature (most important) • 2. Parent Rock - Type and chemical composition • 3. Vegetation - Roots and Leaves • 4. Topography - hilliness, etc. • 5. Time - how long to develop
MATURE VS. IMMATURE SOIL Mature soil is soil that is fully developed! Has a distinguished A,B, and C horizon.Forest soil, Grassland soil, and Tropical Soil Immature soil is soil that is not fully developed! Does not have a distinguished A,B and C horizon. Ex. Desert soil, Arctic soil
PEDALFERS VS. PEDOCALS • Pedalfers - Found in eastern half of U.S. where rainfall exceeds 25 inches/year • a. Ped - soil / Al - aluminum / Fe - ferrum - iron al from clay , fe from iron oxide • 2. Pedocals -
SOILS PROFILE • Soil Profile - a cross reaction of soil down to the bedrock. Almost all soils show a “profile” of 3 distinct layers or zones (A,B,C) • A. “A (horizon)” topsoil, gray or black, has humus • B. “B (horizon)” subsoil, more clay is washed down • C. “C (horizon)” Rock fragments and slightly weathered bedrock • Note: More detailed description in your packet.
SOIL TYPES AND CLIMATE • Soil types and climate • 1.Most important factor affecting soil is the climate • A. Tropical soil - Warm and wet, speed up chemical weathering. Thus soil forms more quickly. Infertile due to leaching because of rain (high temp. and heavy rainfall). Note: 3 meters • B. Grassland soil - enough rain for grass but not trees. Thick A horizon and very fertile. Note: 1 meter • C. Forest soil - Humid regions with cool season. Well developed horizons. Less than 1 meter. Not very fertile. • D. Arctic soils - High elevation and latitude. Very few layers, shallow. Permafrost.
SOIL CONSERVATION B. SOIL CONSERVATION 1. Soil Erosion - movement of topsoil by water and wind 4 bill tons (water), 1 bill tons (wind) = loss of topsoil REDUCE IT!!!! 1. Windbreaks (level plains) 2. Contour farming (plant parallel to land contours 3. Terraces (flattened slopes) 4. Strip cropping 5. No till
RATES OF SOIL FORMATION • Factors of Rates of Soil Formaiton • 1. The rocks themselves - Igneous and metamorphic most resistant, sedimentary least resistant because of pores. • 2. Surface Area • 3. Climate - Warm and wet = chemical weathering • Cold and Dry = mechanical weathering • 4. Topography • 5. Biological Factors