Rocks Weathering and Soil Components 6th Grade Science

Weathering and Erosion Weathering is the process that breaks down rock and other substances at Earth’s surface. Heat, cold, water, and ice all contribute to weathering. The forces of weathering break rock into smaller pieces.

Weathering and Erosion Erosion is the removal of rock particles by wind, water, ice, or gravity Weathering and Erosion work together continuously to wear down and carry away the rocks at Earth’s surface

What is soil? Soil is the loose, weathered material on Earth’s surface n which plants can grow. Soil is a mixture of rock particles, minerals, decayed organic material, and air.

What is soil? Broken down dead plants animals Including rocks

Soil Horizon Horizon is a side profile of the layers of soil Soil is usually divided into 3 main layers (A, B, & C), but will also include the layers above and below for a total of 5 layers.

Soil Horizons Diagram Dark brown/black Reddish brown (clay) Yellowish brown Solid rock

O Horizon: Litter Not really a layer of soil It’s on top of the first layer of soil Contains grass, plants, and animals

A Horizon: Topsoil 1st layer of soil Darkest layer of soil (dark brown or black) Contains humus (organic matter), plant roots, small animals, water, and nutrients for plant growth The darker the soil, the more nutrients it contains

B Horizon: Subsoil 2nd layer of soil Lighter in color (reddish brown) Fewer nutrients and water Limited plant growth

C Horizon: Parent Material 3rd layer of soil Lightest in color (yellowish brown/gray) No nutrients, animals, or plant growth Contains weathered rock and sediment

R Horizon: Bedrock Below the last layer of soil Solid Rock Has not been weathered or broken down yet No soil in this layer

Living Organisms in Soil Some soil organisms make humus, the material that makes soil fertile. Other soil organisms mix the soil and make spaces in it for air and water. Plants: Contribute most to soil humus—supply organic remains, also form the litter

Living Organisms cont. Microorganisms: Break down the remains of dead organisms and mix it with the soil Animals: Break up hard compacted soil and mix humus through it. They add nitrogen and organic material to the soil.