Section 1
Soil Combines Materials to Support Life
Soil forms from weathered rocks, minerals, and decayed plants and animals called humus. This mixture contains water, air, and living organisms that work together to create a vital natural resource.
In this Grade 3 lesson from Science: A Closer Look, Chapter 5, students learn what soil is made of, including weathered rocks, minerals, and humus, and explore the distinct layers of topsoil, subsoil, and bedrock. Students discover how humus adds nutrients and retains moisture, how living things like earthworms and plant roots interact with soil, and why preventing soil erosion matters. The lesson builds key Earth science vocabulary and observational skills through hands-on inquiry.
Section 1
Soil Combines Materials to Support Life
Soil forms from weathered rocks, minerals, and decayed plants and animals called humus. This mixture contains water, air, and living organisms that work together to create a vital natural resource.
Section 2
Soils Develop Distinct Layers Over Time
Weathering breaks rocks into smaller pieces that accumulate in layers. The dark topsoil contains the most humus, followed by lighter subsoil, and finally bedrock. Just one centimeter takes up to 1,000 years to form.
Section 3
Different Soils Hold Various Amounts of Water
Soil texture determines water retention. Clay soil, with the smallest grains, holds the most water, while sandy soil holds very little. Loam, a balanced mixture of sand, silt, and clay, provides ideal moisture for most plants.
Section 4
Living Things Depend on Soil to Survive
As a natural resource, soil provides habitat for organisms like earthworms and enables plants to grow. Without soil, we would lack food, building materials, clothing fibers, and many medicines derived from plants.
Book overview
Jump across lessons in the current chapter without opening the full course modal.
Continue this chapter
Expand to review the lesson summary and core properties.
Section 1
Soil Combines Materials to Support Life
Soil forms from weathered rocks, minerals, and decayed plants and animals called humus. This mixture contains water, air, and living organisms that work together to create a vital natural resource.
Section 2
Soils Develop Distinct Layers Over Time
Weathering breaks rocks into smaller pieces that accumulate in layers. The dark topsoil contains the most humus, followed by lighter subsoil, and finally bedrock. Just one centimeter takes up to 1,000 years to form.
Section 3
Different Soils Hold Various Amounts of Water
Soil texture determines water retention. Clay soil, with the smallest grains, holds the most water, while sandy soil holds very little. Loam, a balanced mixture of sand, silt, and clay, provides ideal moisture for most plants.
Section 4
Living Things Depend on Soil to Survive
As a natural resource, soil provides habitat for organisms like earthworms and enables plants to grow. Without soil, we would lack food, building materials, clothing fibers, and many medicines derived from plants.
Book overview
Jump across lessons in the current chapter without opening the full course modal.
Continue this chapter