Unit 3: Rocks, Soil, & Minerals

1
Unit 3 Rocks, Soil, Minerals
2
Weathering

• Weathering
• the process that breaks down rock other
  substances _at_ Earths surface.
• Heat, cold, water, ice, oxygen, and carbon
  dioxide contribute to weathering.

3
Forces

• Forces of weathering break rocks into smaller
  pieces
• Forces of erosion carry these pieces away.

4
Erosion

• Erosion
• the movement of rock particles by wind, water,
  ice, or gravity.
• Weathering and erosion work together to wear down
  and carry away rocks at Earths surface.

5
Concept Check

• What is the difference between weathering and
  erosion?

6
2 Types of Weathering

• Mechanical Weathering
• Rocks are physically broken down into smaller
  pieces.
• Occurs slowly over time, but can wear away a
  whole mountain.
• Chemical weathering
• Breaks down rock through chemical changes.
• Agents include water, oxygen, carbon dioxide,
  living organisms, and acid rain.

7
Forces of Mechanical Weathering

• Release of Pressure
• As mass is removed, pressure is reduced and the
  outside layer of rock flakes away.
• Freezing and Thawing
• Deals with temperature changes
• Abrasion
• The grinding away of rock particles carried by
  water, ice, wind, or gravity.
• Plant growth
• Roots of plants enter cracks in rocks and causes
  the rock to pry apart.
• Animal actions
• When animals burrow into the ground it loosens up
  soil and breaks apart rock.

8
Agents of Chemical Weathering

• Water
• Most important
• Dissolves rock
• Oxygen
• Oxidation
• E.g. iron ? rust
• Carbon dioxide
• Forms carbonic acid when mixed with rain water on
  the ground
• Living organisms
• Produce acids that chemically weather rock
• Acid rain
• When the burning of fuels produces pollutants,
  these harsh gases combine with rain and form
  acids which weather very quickly.

9
Mechanical Chemical Together

• Mechanical and chemical weathering often work
  together
• Mechanical breaks rocks down, exposing more of
  the rock or mineral to chemical weathering.
• Rate of weathering is determined by
• Type of rock
• More permeable weathers faster
• Temperature (remember the vinegar chalk)
• High temps high precipitation level faster
  weathering

10
As the surface area of this rock is increased by
mechanical weathering, it is more exposed to
agents of chemical weathering
11
Climate

• Both types of weathering occur faster in hot, wet
  climates.
• Rainfall provides the water needed for chemical
  changes as well as freezing and thawing.
• Chemical reactions occur faster at higher
  temperatures.

12
Examples of the Effects of Weathering

• Look at the following examples of weathering.
  Which type of weathering do you think occurred?
  Why do you think that?

13
Example 1
14
Example 2
15
Example 3
16
Example 4
17
Example 5
18
Example 6
19
Example 7
20
Example 8
21
Example 9
22
Now you come up with your own example
23
Soil

• Soil is the loose, weathered material on Earths
  surface in which plants can grow.
• It forms as a rock is broken down by weathering
  and mixes with other materials on the surface.

24
Soil Composition

• Soil
• mixture of rock particles, minerals, decayed
  organic material, air, and water.
• Type of rock particles and minerals in any given
  soil depend on
• The rock weathering
• Type of weathering that took place

25
Soil Texture

• Depends on the size of individual soil particles
• E.g. sand vs. clay
• Particles are classified by size
• Gravel largest (2mm and above)
• Sand
• Silt
• Clay smallest

26
Checkpoint

• Looking back at the particle size of different
  types of soil, why do certain types have the
  texture (feel) they do? Give an example.

27
Soil Texture

• Important for plant growth.
• Clay is dense and heavy and typically holds a lot
  of water.
• Sand is coarse and water drains quickly.
• Loam is a type of soil that is an equal mix of
  sand, clay, and silt.
• Best for growing plants

28
Soil Horizons

• 3 horizons
• Topsoil mix of humus, clay, other materials.
• Subsoil mix of clay and little humus
• Bedrock partly weathered rock

29
Life in Soil

• Organisms mix the soil and make spaces in it for
  air and water. Other soil organisms make humus,
  the material that makes soil fertile.

30
Soil Activity

• http//School.discoveryeducation.com/schooladventu
  res/soil

31
Soil Observations

• Explain your soils
• Color
• Texture
• Particle size (what do you think it has the most
  of look back at your notes)
• Original location
• Original depth (remember the horizons)
• What type of plant would grow the best in it

32
Importance of Soil

• Soil is one of Earths most valuable resources
  because everything that lives on land depends
  directly or indirectly on soil.
• Plants
• Animals
• Humans

33
Importance of Soil

• Long time to form
• Limited supply of fertile soil
• Designates where farming can take place

34
Soil Damage and Loss

• Can be lost to erosion by water and wind.
• Water where soil isnt protected by a plant
  cover.
• Wind occurs in dry climates (e.g. dust bowl)

35
The Dust Bowl

• Plowing removed the grass from the Great Plains
  and exposed the soil.
• In times of drought, the topsoil quickly dried
  out, turned to dust, and blew away.

36
(No Transcript)
37
Soil Conservation

• The management of soil to prevent its destruction
• 2 methods
• Contour plowing plowing along the curves of a
  slope
• Conservation plowing old crops and dead weeds
  are left in the crop
• Also, limiting herd grazing

38
Diamond Formation

• At depths of 120 kilometers
• Under great pressure and heat
• This caused carbon atoms to change into diamonds
• Originated from a volcanic pipe

39
3 Main Ways Minerals Form

• As hot magma cools inside the crust or as lava
  hardens on the surface
• When the elements of a mineral dissolve in hot
  water (forms a solution)
• When solutions evaporate

40
Processes of Mineral Formation

• Minerals have been forming since the beginning of
  Earth
• Minerals can form in 2 ways
• Through crystallization of materials dissolved in
  water
• Through crystallization of melted materials

41
Uses of Minerals

• Minerals are the source of metals, gemstones, and
  other materials used to make many products.
• Ore
• A rock that contains a metal or economically
  useful mineral
• E.g. Copper comes from the ore chalcopyrite