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NO CALCULATORS PLEASE and SHOW ALL OF YOUR WORK
Calculative Questions for Chapter 15 – Soil Resources
1. If soil loss from erosion is 2.5 cm over 20 years in a particular region and if 1 mm of topsoil in an land
area of 1 hectare weighs 13.0 metric tons, how many metric tons of topsoil will be loss per hectare in 20
years in that region.
a) 2.5 metric tons
b) 32.5 metric tons
c) 260 metric tons
d) 325 metric tons
e) 650 metric tons
There are 10 mm per cm.
2.5 cm/20 yrs * 10 mm/cm = 25 mm/20 yrs
13 metric tons/mm/hectare * 25 mm/20 yrs = 325 metric tons/hectare/20 yrs
2. If the rate of soil formation is 1 metric tons/hectare/year, how long will take to replace 2 cm of soil, given
that 1 mm/hectare of soil weighs 13 metric tons.
a) 13 years
b) 26 years
c) 260 years d) 1300 years e) 2600 years
1 metric ton/hectare/year divided by 13 metric tons/mm/hectare = 0.0769 mm / year
2 cm * 10 mm / cm = 20 mm
20 mm divided by 0.0769 mm / year = 260 years
3. If you examined 100 lbs of soil, approximately how many pounds would be mineral particles, organic
materials, water and air?
a) 45-5-25-25 lbs respectively c) 30-10-30-30 lbs respectively
b) 25-25-5-45 lbs respectively d) these amounts are impossible to calculate without additional information
this is a simple application of percentages within 100 lbs.
4. If the largest sand particles are about 2mm in diameter, how much larger are they than the largest particles
of silt (0.05mm in diameter)?
a) 0.1x as large
b) 10x as large
c) 25x as large
d) 40x as large
2mm / 0.05mm = 40
5. If approximately 2.5 cm of soil on average is lost by erosion in the US within a twenty year period, how
much soil is lost each year?
a) 0.13cm
b) 0.5cm
c) 13cm
2.5cm / 20 yrs = 0.125cm/yr
d) 50cm