Soil Formation and Composition. Biotic (living) Abiotic (nonliving) . 1. Make a table and list 5 examples of each. Soil Formation. Soil is the loose, weathered material on Earth’s surface in which plants can grow. It is formed wherever bedrock is exposed.
1. Make a table and list 5 examples of each
Soil is more than just weathered rock.
Soil is a mixture of rock particles, minerals, decayed organic materials, air, and water.
All soil is NOT the same - it depends on the bedrock that it was weathered from and the type of weathering.
The dead organic material is broken down by decomposers to form humus by decomposition.
Humus helps create spaces in soil for air and water.
2. Draw the flowchart and fill it in as you go through it.
Acid Carbon dioxide
Smaller rock particles
Particles with different mineral make up
Mix with other materials on the surface
Soil texture depends on the size of the individual soil particles.
Soil particles range in size from gravel to clay particles too small to be seen by the unaided eye.
The sand, silt, and clay shown here have been enlarged.
Permeability is a measure of the ease with which fluids will flow though a porous rock, sediment, or soil.
Although a rock may be highly porous, if the voids are not interconnected, then fluids within the closed, isolated pores cannot move.
Porosity is the ratio of the volume of openings (voids) to the total volume of material. Consists of the spaces between the grains
The larger the pore space or the greater their number, the higher the porosity.
The more tightly packed the grains are, the lower the porosity.
A soil horizon is a layer of soil that differs in color and texture from the layers above or below it.
They form over long periods of time. Think centuries not decades.
It can take a hundred years for just a few centimeters of soil to form.
The C horizon forms 1st as bedrock weathers and rock breaks up into soil particles.
The A horizon
develops from theChorizon
when plant roots weather the rock mechanically and chemically.
Plants also add dark, organic material to the soil that is a mixture of humus, clay, and other minerals
The B horizon develops as rainwater washes clay and minerals from the A horizon to the Bhorizon. Contains little humus.
3. As the topsoil and subsoil develop, what happens to the bedrock?
4. Make a sketch of the three horizons and label each.
5. Which living things contribute most ofthe organic materials that form humus?Life in Soil
6.How do decomposers contribute to the formation of soil?
7. What role do earthworms play in the formation of soil?
8. Which organisms break up hard, compacted soil and mix humus through it?
Fungi - molds & mushrooms, grow on and digest plant remains
Bacteria - microscopic, attack dead organisms and their waste
Earthworms - mix humus to aerate the soil. They also eat soil and eliminate it as waste that are enriched in nutrients.
9. Draw the flowchart in your notebook and fill in the blanks.
is made of
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