Page 75 - Science Course 2 (Book 2)

Mo10-L1a: What are the Materials in Earth’s Geosphere?

Soil is the loose, weathered material in which plants
grow.

A – Horizon

B – Horizon

C – Horizon
Wastes from organisms and the decaying bodies
of dead organisms provide soil with nutrients that
makes it more fertile.

A major part of the organic matter in soil is carbon
that plants obtain from the atmosphere through
A–Horizon photosynthesis.
The A–horizon is the part of the soil that you are
the most likely to see when you dig a shallow hole Soil plays a major role in the phosphorus and carbon
in the soil with your f ngers. Organic matter from cycles.
the decay of roots and the action of soil organ-
ism often makes this horizon excellent for plant
growth. Because the A-horizon contains most of
the organic matter in the soil, it is usually darker
than other horizons.

B–Horizon
When water from rain or snow seeps through
pores in the A-horizon, it carries clay particles.
The clay is then deposited below the upper layer,
forming a B-horizon. Other materials also accu-
mulate in B-horizons.

C–Horizon
The layer of weathered parent material is called Interactions among all Earth systems take place in
soil because soil contains minerals, water, air, and
the C-horizon. Parent material can be rock or organisms, all in close contact.
sediments.

Soil layers form as rock is slowly transformed into SUMMARY
soil. What are the Materials in Earth’s Geosphere?

Soil formation begins when Minerals are the basic building blocks for
rocks weather into sediment materials in the geosphere, including soil, rock,
and water dissolves minerals and metal.
and other materials from the
sediment.

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