WEATHERING AND SOIL
Weathering is the breaking of rocks into smaller fragments. It wears mountains down over millions of
years and affects naturally formed rocks and human structures.
Mechanical weathering breaks apart rocks without changing their chemical composition. They remain
the same, the size is different. This can be done by the force of running water, forcing rocks to hit each
other and break apart. Plants can cause mechanical weathering when tree roots or plants get in a crack
and as they grow they force the rock apart. A good example is a sidewalk…over time it cracks and is
uneven. Ice wedging is another form of mechanical (physical) weathering. When water gets into a
crack of a rock and freezes it expands forcing the rock apart. When this continuously repeats during
freezing and thawing it will break apart. You can see that causing potholes.
Chemical weathering occurs when water, air or other substances react with the minerals. Water is the
main agent of chemical weathering. When water comes in contact with some minerals, a new mineral
may form.
Oxidation is when a metal such as iron is exposed to oxygen and water and forms a new material, in this
case rust.
Another type of weathering occurs when natural acids come in contact with rocks. When water mixes
with carbon dioxide from the air, carbonic acid is formed which dissolves limestone which makes caves.
Some plants also secrete acids through their roots and dissolve rocks over time.
The climate plays a big part on weathering. It occurs all around the world; however how fast it occurs
depends on the weather. In cold regions where there is thawing and freezing you will get ice wedging.
In areas that have a lot of moisture and warm temperatures, you will have more chemical weathering
occurring. Chemical weathering occurs more frequently in tropical climates.
Soil is a mixture of weathered rock and organic matter along with mineral fragments, water and air. It
can take thousands of years to form and varies in thickness from a few centimeters to 60 meters in
depth. As rock weathers into smaller and smaller fragments, plants begin to grow. Then worms, insects,
bacteria and fungi begin living among the plants. They held the soil to evolve by adding organic matter.
Humus is the dark colored organic material made up of decaying plants and animals.
A soil profile is the layers of soil. Plants usually grow in the dark top layer of the soil called the A
Horizon. It is also called topsoil and is usually more evolved than other layers. It has more humus and
smaller sediments. The B horizon is less evolved and is lighter in color since it has no or little humus.
Some plant roots will reach down into this layer. This usually contains minerals that were washed down
from the A horizon in a process called leaching. It is like a coffee pot and picks up dissolved minerals on
its way down. The C Horizon is at the bottom and contains no organic material. It contains partly
weathered rock. Below this is the bedrock—solid rock.
_______________is the breaking of rocks into _________________fragments. It wears mountains
down over millions of years and affects naturally formed rocks and human structures.
________________________l weathering breaks apart rocks _________changing their chemical
composition. They remain the same, the size is___________. This can be done by the force of
running___________, forcing rocks to hit each other and break apart. ________can cause mechanical
weathering when tree roots or plants get in a crack and as they grow they force the rock apart. A good
example is a sidewalk…over time it cracks and is uneven. ____________ is another form of mechanical
(physical) weathering. When water gets into a crack of a rock and freezes it _________forcing the rock
apart. When this continuously repeats during freezing and thawing it will break apart. You can see that
causing___________.
_________________weathering occurs when water, air or other substances react with the minerals.
_________is the main agent of chemical weathering. When water comes in contact with some minerals,
a new mineral may form.
Oxidation is when a metal such as iron is exposed to ________and water and forms a
____________material, in this case rust.
Another type of weathering occurs when natural acids come in contact with rocks. When _______
mixes with carbon dioxide from the air, carbonic acid is formed which dissolves limestone which makes
caves. Some _______also secrete acids through their roots and dissolve rocks over time.
The ________plays a big part on weathering. It occurs all around the world; however, how _______it
occurs depends on the weather. In cold regions where there is thawing and freezing you will get ice
wedging. In areas that have a lot of moisture and _______temperatures, you will have more chemical
weathering occurring. Chemical weathering occurs more frequently in _________climates.
_________is a mixture of weathered rock and __________ matter along with mineral fragments, water
and air. It can take thousands of years to form and varies in thickness from a few centimeters to 60
meters in depth. As rock weathers into smaller and smaller fragments, plants begin to grow. Then
worms, insects, bacteria and fungi begin living among the plants. They help the soil to _________by
adding organic matter. ________is the dark colored organic material made up of decaying plants and
animals.
A soil profile is the__________________________. Plants usually grow in the ________ top layer of the
soil called the ______ Horizon. It is also called _________ and is usually more evolved than other
layers. It has ________humus and smaller sediments. The ____horizon is less evolved and is _______
in color since it has no or little_______. Some plant roots will reach down into this layer. This usually
contains minerals that were washed down from the A horizon in a process called_________. It is like a
coffee pot and picks up dissolved minerals on its way down. The ______ Horizon is at the bottom and
contains _______organic material. It contains partly weathered rock. Below this is the________—solid
rock.