Stability of earth materials on slopes depends on the balance of gravitational and frictional forces. Which of the following does NOT have a measurable effect on the balance between gravity and friction?
a) type of rock or sediment that is making up the slope
b) presence of water
c) types of vegetation on the slope
d) atmospheric air pressure
e) steepness of a slope

The correct answer is d) atmospheric air pressure .

Explanation:

The atmospheric pressure, also known as barometric, is what causes the weight of the mass of air that is acting on the earth.

This value will be higher or lower, depending on the altitude at which we are, with reference to the lowest point considered, which is usually the sea level, but is also influenced by some atmospheric effects produced by the circulation of currents of warm or cold air.

Theoretically, it is considered that the maximum value of atmospheric pressure is achieved at sea level, although in some parts of the earth there are areas below that level. Its value at this point corresponds to 1013 mbar or 760 mm Hg. The value of 1 atmosphere (atm) is also commonly used as a reference unit, but is not included in the International System of Units.

It is also known as barometric pressure, due to the instrument used for its measurement. It was Evangelista Torricelli who in 1643 invented the first barometer, although the name was given by Edme Mariotte some years later.