Download How Soil Forms Notes

Name: ______________________________________________ Period:____________
Chapter 2 Section 2 Geology
Note Guide: How Soil Forms
1] What is Soil?
a. ________________________ is the loose, weathered material on Earth’s surface
in which plants grow.
b. One of the main ingredients of soil is:
_______________________ which is the solid layer of rock beneath the soil.
2] Soil Composition
a. Soil is comprised of a mixture of rock, particles, ________________________,
decayed organic material, water and air.
b. The decayed organic material in soil is called ___________________________.
Humus provides plants with the nutrients they need to grow.
c. Soil that is rich in humus has a _____________ __________________ rate
supporting plant growth.
3] Soil Texture
a. Soil texture depends on the ______________________ of the individual particles.
b. The largest particle size is __________________________.
c. The smallest __________________________ size is clay.
d. _____________________ is the best type of soil for growing plants since it is
made up of about equal parts of clay, sand and silt.
4] The Process of Soil Formation
a. Soil forms as rock is broken down by __________________
and mixes with other materials.
b. 3 horizons (layers)
A horizon: ___________________
_______________________: subsoil
C horizon: partly _______________________rock
5] Horizon A
a. Horizon A is made up of ______________________________.
b. Topsoil is a crumbly, dark brown soil that is a mixture of ___________________,
clay and other materials.
c. This soil horizon is most important for growing _________________________.
6] Horizon B
a. Horizon B is consists of clay and other particles washed
down from Horizon A; very little __________________.
b. Horizon B is often called _________________________.
c. ______________________ forms last as particles wash
down from the A horizon.
7] Horizon C
a. Horizon C is ______________________________ rock.
b. The ______________________ is most similar to bedrock.
c. It consists mostly of pieces of __________________________.
8] Rate of Soil Formation
a. The rate of soil formation depends on the _______________________ and
____________________.
b. Weather occurs most rapidly in areas with a ________________,
_________________ climate so soil will form faster in these areas.
c. Soil forms more quickly from limestone than granite since limestone weathers
faster.
9] Soil Types
Classified based on ___________________, ___________________ and
____________________________.
10] Types of Soil
a. ________________________ soil forms in regions with hot, wet climates.
b. Thin soil forms in mountains and polar regions with ____________ and
_____________climates.
c. The thickest and most fertile soil forms in moderate temperatures with
__________________
_____________________.
11] Major Soil Types in North America
a. Forest b. ____________ c. Desert d. ____________ e. ____________ f. Tropical
12] Living Organisms in Soil
a. Two ways organisms contribute to soil:
1. ________________________________________
2. ________________________________________
13] Forming Humus
a. ____________________contribute most of the organic remains that form humus.
b. As plants shed leaves, they form a loose layer called _______________________.
c. Humus forms in a process known as _________________________ where
organisms that live in the soil turn dead organic material into humus.
d. ____________________________are the organisms that break down the remains.
These include _______________, bacteria, _____________, and other organisms.
14] Mixing the Soil
a. _________________________ mix humus with
other materials in soil.
b. They also help move air and water into the soil
through a process called
__________________________.