Soil Formation & Composition Notes
Catalyst:
What do you think soil is and where do you see soil in your life?
How might soil be related to flooding?
Review Questions:
How does surface area affect the rate of weathering? ______
What is soil? ______
Mini-Lesson:
Weathering has attacked the rocks of Earth’s surface since the beginning of geologic time. Soil is made of loose, weathered ______and ______material in which plants with roots can grow.
Soil Composition
The rock material in soil contains three noticeable parts:
The amount of each of these three can affect the soil’s ability to hold ______and ______, both of which are essential for plant growth.
Vertical Sorting:
What is it?
How do layers form?
What three properties determine how vertical sorting occurs?
ALL SOILS ARE DIFFERENT AND HAVE DIFFERENT PROPERTIES!!!!
To determine the type of soil you must follow these steps:
1.
2.
3.
4.
Runoff / InfiltrationSaturated / Unsaturated
High Gradient / Low Gradient
Low Porosity
/ High Porosity
Low Permeability / High Permeability
Same column = ______relationship (both ______)
Different column = ______relationship (______goes up, ______goes down)
CAPILLARITY
High Capillarity / Low CapillaritySmall sediment / Large sediment
Practice Part 1:
Fill in the blanks:
As soil saturation increases, runoff ______
As soil saturation increases, infiltration ______.
As soil permeability increases, runoff ______
As soil permeability increases, infiltration ______
The higher the gradient, the more ______
The flatter the surface, the more ______
If land is unsaturated, there will likely be more ______than ______
As the size of sediment decreases, capillarity ______
Common experimental set up
Base your answer on the accompanying diagram, which shows four tubes containing 500 milliliters of sediment labeled A, B, C, and D. Each tube contains well-sorted, loosely packed particles of uniform shape and size and is open at the top. The classification of the sediment in each tube is labeled.
Question example:
Water will be able to infiltrate each of these sediment samples if the sediment is
1. saturated and impermeable 3. unsaturated and impermeable
2. saturated and permeable 4. unsaturated and permeable
ROCKS
When soil has low porosity, low permeability, high gradient, and is saturated, runoff will occur
When soil has high porosity, high permeability, low gradient, and is unsaturated, infiltration will occur
When particle size decreases, capillarity increases
Practice Part 2:
1. Soil composed of which particle size usually has the greatest capillarity?
1. silt 3. coarse sand 2. fine sand 4. Pebbles
2. The accompanying diagram shows a laboratory setup. The rubber band holds filter paper across the base of the open tube to hold the soil sample. The tube was placed in the water as shown. The upward movement of water is represented by arrows. The height of the water that moved upward within the soil was measured. Students repeated this procedure using soils with different particle sizes. Results of the experiment are shown in the data table.
Results of this experiment lead to the conclusion that
capillarity is greater in soils with large particles
permeability is greater in soils with larger particles
capillarity is greater in soils with smaller particles
permeability is greater in soils with smaller particles
3. Which graph shows the effect of soil permeability on the amount of runoff in an area?
4. Which surface soil type has the slowest permeability rate and is most likely to produce flooding?
1. pebbles 2. silt 3. sand 4. Clay
Which graph best represents the general relationship between soil particle size and the permeability rate of infiltrating rainwater?
Why?
5. Compared to an area of Earth's surface with gentle slopes, an area with steeper slopes most likely has
1. less infiltration and more runoff 3. more infiltration and more runoff
2. less infiltration and less runoff 4. more infiltration and less runoff
Why?
6.The greatest amount of rainwater infiltration occurs on the side of a hill if the surface of a permeable soil has
1. small soil particles and a steep slope 3. large soil particles and a steep slope
2. small soil particles and a gentle slope 4. large soil particles and a gentle slope
Why?
7. The diagrams (see image) represent four permeable sediment samples. The sediments are composed of the same material, but differ in particle size and sorting. Which sediment sample will most likely have the fastest groundwater infiltration rate?
Why?
8. Which set of conditions would produce the most runoff of precipitation?
1. gentle slope and permeable surface 3. steep slope and permeable surface
2. gentle slope and impermeable surface 4. steep slope and impermeable surface
Why?
9. The columns A, B, C, and D shown in the accompanying diagram contain equal volumes of sediment.
When an equal volume of water is added to each column, the greatest rate of infiltration will occur in which column?
1. A 2. B 3. C 4. D
10. Which condition would cause surface runoff to increase in a particular location?
1. covering a dirt road with pavement 3. planting grasses and shrubs on a hillside
2. reducing the gradient of a steep hill 4. having a decrease in the annual rainfall
Why?
11. Compared to an area of Earth's surface with gentle slopes, an area with steeper slopes most likely has
1. less infiltration and more runoff 3. more infiltration and more runoff
2. less infiltration and less runoff 4. more infiltration and less runoff
Why?
12. During a heavy rainstorm, runoff is most likely to occur if the surface soil is
1. firmly packed clay-sized particles 3. covered by trees, shrubs, and grasses
2. loosely packed sand-sized particles 4. unsaturated and has a gentle slope
Why?
** HOMEWORK **:
Using what you know about soils, write “A Day in the Life of a Soil” in which you take on the role of a rock being weathered, and becoming a soil. Who are your parents? What do they look like? What type of soil are you? What color and composition are you?