Answer
Downslope tree trunks are curved due to the process of creep. Creep is a slow, gradual downslope movement of soil or regolith, which occurs over time. As soil particles expand and contract during freeze-thaw or wet-dry cycles, they slowly move downslope. The curved shape of tree trunks results from their attempt to maintain an upright position as the ground beneath them moves slowly. Trees can exhibit curvature as they grow and adapt to the ever-changing slope caused by creep. On the other hand, fences, utility poles, and walls are typically installed vertically or horizontally, perpendicular to the ground. As the ground beneath them moves due to creep, they are either tilted or displaced sideways because they are rigid structures unable to adjust to the slow movement of the soil.
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