Which human-caused change might be considered a catastrophic change rather than a gradual change? 

A)  compaction of the soil by continued exposure to heavy farm machinery 
B)  salinization of the soil though evaporation of water and deposition of salt 
C)  plowing of prairie soil to commence agriculture 
D)  human-caused changes associated with wind and water erosion

Catastrophic Change

A sudden and widespread disaster that can cause significant environmental, economic, or social upheaval.

Soil Salinization

The accumulation of soluble salts in soil to levels that negatively impact agricultural productivity, often caused by improper irrigation practices.

Compaction

Compaction is the process of applying force to compress soil or material, which increases density and stability, but can affect water infiltration and root growth.