Periglacial Geomorphology – Freeze–thaw driven downslope movement What is the term for the slow downslope displacement of soil and sediment caused specifically by frost heaving during freezing and subsequent settling during thaw?

Introduction / Context:
Periglacial environments exhibit mass-movement processes driven by freeze–thaw cycles. Differentiating among frost creep, solifluction, and gelifluction is important for understanding slope evolution, infrastructure stability, and soil transport in cold regions.

Given Data / Assumptions:

• Mechanism highlighted: frost heaving during freezing and settling (contraction) during thaw.
• Movement is slow and involves soil/sediment, not large blocks plunging downslope.
• We must match process name to mechanism.

Concept / Approach:
Frost creep results from needle-ice growth and volumetric expansion lifting particles perpendicular to slope during freezing, followed by vertical settling during thaw. Because lifting is perpendicular and settling is vertical, there is a small net downslope shift each cycle. Solifluction is the slow viscous flow of saturated regolith on gentle slopes, often in seasonally thawed active layers over permafrost. Gelifluction is solifluction specific to permafrost terrains. Rockfall is rapid, discrete movement of rock blocks, not a slow creep process.

Step-by-Step Solution:
Focus on the freeze–thaw micro-mechanics: heave up-slope normal, settle vertical.Infer net downslope displacement per cycle → frost creep.Eliminate water-saturation flow (solifluction/gelifluction) and rapid mass wasting (rockfall).

Verification / Alternative check:
Field stakes in periglacial slopes show millimetres to centimetres of annual downslope movement consistent with frost creep where moisture is present but not fully saturated for flow.

Why Other Options Are Wrong:

• solifluction: saturated, viscous flow; mechanism is not heave-settle creep alone.
• gelifluction: permafrost-context solifluction; again a flow process.
• rockfall: fast, catastrophic detachment, not slow creep.

Common Pitfalls:
Labeling all slow movements on cold slopes as solifluction; assess saturation and permafrost presence to distinguish processes.

Final Answer:
frost creep