Mass Wasting Speed Ordering

Mass wasting refers to the downslope movement of rock, regolith, and soil under the direct influence of gravity. The speed at which these processes occur varies significantly.

Analyzing Mass Wasting Speeds

To determine the correct sequence in decreasing order of speed (fastest to slowest), we analyze the typical velocities:

• Rockfall: This involves the rapid, free-falling or tumbling of rock fragments down a steep slope or cliff. It is characterized by very high speeds, often occurring suddenly.
• Earth flow: This type of mass wasting involves the downslope movement of soil and regolith, often saturated with water, forming a lobe-like shape. While slower than rockfall, it moves considerably faster than creep. Speeds can range from slow to rapid depending on water content and slope steepness.
• Creep: This is the slowest and most gradual type of mass movement. It involves the imperceptible downslope displacement of soil and regolith over long periods, often evidenced by tilted trees or fences.

Determining the Correct Sequence

Based on the analysis of speeds:

• Fastest: Rockfall
• Intermediate: Earth flow
• Slowest: Creep

Therefore, the correct sequence of mass wasting in decreasing order of speed is Rockfall -- Earth flow -- Creep.