What is weathering? Breaking down of rocks & other materials on Earth’s surface
Rate of Weathering Factors Affecting Rate of Weathering Climate Faster in hot, wet climates Surface Area Faster with small pieces Rock Composition Faster with minerals in limestone, iron Chemical Reactions Faster with certain chemicals
How does weathering affect soil? Weathering causes bedrock to break down and become an ingredient in soil.
What is soil? Soil: mixture that includes silt, sand, & clay
Soil is not DIRT! Dirt is what you track in on your mother's floor, soil is what plants grow in. A scientist would not use the word "dirt" for the surface layer of the ground where plants grow, that is "soil."
Bedrock: solid rock that lies below the soil. Bedrock is the PARENT MATERIAL of soil.
Why is soil important? Supports human needs such as houses, buildings, roads, crops, & grazing animals.
How do soils differ? Properties of Soils Texture Size of soil particles ColorHue of soil Composition Ingredients that make up soil Permeability Movement of air & H2O through soil Porosity Space between soil particles
Soil Property #1: Texture Size of soil particles
Soil Property #3: Composition Ingredients that make up the soil
Soil Property #4: Porosity how much space there is between soil particles H2O can be held tighter in small spaces or pores (clay) than in large spaces (sand). Think of a sieve. Smaller screens hold more water.
Soil Property #5: Permeability how easily air & water move through soil Water quickly drains through coarse, loose soils like sand. Water slowly drains through fine, firm soils like clay.
What determines the type of soil? The type of minerals & parent materials that make up the bedrock. Weathered granite forms different soil than weathered limestone. Climate Click on pic
What affects minerals in soils? Leaching: removing or washing away of the minerals in soil On farms, these minerals need to be replaced so crops will grow. Farmers add fertilizers to replace the minerals use by plants
What is a soil profile? Soil Profile: all the layers that make up the soil in an area Horizon: soil layers
Soil Profile O Horizon: thin coating or ORGANIC material (loose leaves, decaying plants/animals) A Horizon: topsoil, a mixture of humus & rock particles. Dark in color. B Horizon: subsoil, clay, small pieces of weathered rock, & minerals C Horizon: bottom layer made of large pieces of rock that have come from weathered bedrock R = Bedrock: solid rock that lies below the soil Click on pic
Soil Uses Uses of soils depend on their properties Click on pic