Mass movements, erosion, and deposition

Mass movement is driven mainly by gravity on slopes, while erosion involves transport by water, wind, or ice. In exams, use gravity as the key clue.

Saturation makes slope material heavier and weaker, so failure becomes easier. Link pore-water pressure with slope failure in exams.

Slump is rotational, whereas translational sliding occurs along a relatively planar slip surface. In exams, curved failure surface identifies slump.

Ice action in joints can loosen rocks on steep cliffs and cause falling. In exams, connect steep slopes and joints with rock fall.

When the slope of loose material exceeds its stable limit, movement may begin. Link angle of repose with slope stability in exams.

Toe erosion removes support from the lower slope, allowing material to slide. Treat river undercutting as a landslide trigger in exams.

Water may accumulate above an impermeable layer and weaken regolith. Remember drainage and slip surface together in exams.

Loss of roots weakens soil, and increased runoff enhances erosion. Link deforestation with both erosion and landslides in exams.

Debris flow moves as a water-rich flow, while rock fall is the detachment and falling of rocks. Identify movement style and material condition in exams.

Seismic shaking can disturb balance along a weak plane. In exams, treat weak plane plus shaking as a combined landslide condition.

Sheet erosion removes a thin layer of soil over a broad surface. In exams, treat it as an early form of water erosion.

Rills enlarge into deeper gullies that are hard to remove by ordinary cultivation. Remember the difference in size and depth for exams.

When energy decreases, heavier particles settle first, while finer particles may travel farther. Link particle size with river energy in exams.

In the upper course, steep gradient helps the river cut downward strongly. Connect gorges with vertical erosion in exams.

Velocity is higher on the outer bank and lower on the inner bank. Remember outer erosion and inner deposition in exams.

When the meander neck is cut, the river takes a straighter course and the old loop becomes a lake. Include both erosion and deposition in exams.

As a stream exits mountains onto plains, velocity drops and sediment spreads like a fan. Write gradient change as the main cause in exams.

During floods, energy drops near the channel edge and coarse particles settle quickly. Link levees with flood deposition in exams.

Base level is the limit below which a river generally cannot erode. In exams, remember sea level as the ultimate base level.

Uplift or fall in base level can make a river cut downward again and form terraces. Link rejuvenation with renewed vertical erosion.

In a graded profile, the river adjusts between energy and load. In exams, understand it as dynamic rather than fixed balance.

Deflation removes fine particles and leaves larger stones on the surface. Link desert pavement with wind erosion in exams.

Wind-blown sand is more effective near the ground and cuts the base. Write it as a result of wind abrasion in exams.

Barchan horns generally extend downwind in the direction of prevailing wind. Use the horns to identify wind direction in exams.

Loess is a wind-deposited fine dust that often forms fertile soil. Link it with aeolian deposition in exams.