Download weathering and soil notes

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.
CHAPTER 5 STUDY GUIDE: WEATHERING AND SOIL
___________________is the breaking of rocks into ______________________fragments. It wears mountains down
over millions of years and affects naturally formed rocks and human structures.
___________________________ 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.