Slope Evolution and Forms

Slope Evolution & Forms

The balance of slope processes and slope forms is determined by I & O from the hill slope.

坡面過程及坡面形態的平衡是取決於山坡的投入與產出

3 situations:

1. I > O :

– thickening of the regolith, + instability, transportation may occur later

– 風化層增厚, +不穩定性, 搬送作用稍後會出現

2. O > I :

– continuing transportation lead to thinning of the regolith

– 搬送作用持續使風化層減薄

3. I = O :

– TR = WR,

– debris maintained

– 碎屑滯留在坡面上

Derived 2 control factors of slope

1. Weathering風化 (weathering-limited slope)

l Low WR, high TR = weathered material keep moving away

l 低WR, 高TR = 風化物質持續被運送

l → straight slope profile

l →垂直的坡面

l exists in regions w/ active transportation & limited weathering, underlaid by resistant bedrock

l 在搬送作用活躍及風化作用有限的地區, 以及表土下有抗蝕母岩的地區出現

2. Transport搬送 (transport-limited slope)

l Low TR, high WR, regolith accumulated, burying the bedrock & reduce weathering

l 低TR, 高WR, 風化層積厚, 覆蓋著母岩並減少風化作用

l → convex upslope

l → 凸上坡

l exists in regions w/ weak rock which produce lowland topography

l 在弱石的低地可見

l slow movement like soil creep occurs on an initially straight slope, leads to the accumulation of regolith along the downslope path and limited the lower slope weathering

l 緩慢移動如土蠕在原先的垂直坡面上, 令風化層開始沿下坡堆積, 並限制了下坡的風化

l relatively rapid WR on upslope produce transportation possibility and develop an upslope convexity

l 上坡出現相對地較快的WR, 令搬移作用變得可能, 並發展成為凸上坡

Slope evolution (3 dev models)

Slope develop can be predictable, equilibrium form is developed through time, peneplain should be the end product.

坡面發展可被推測, 均衡的坡面形態隨時間發展而成, 最後成為準平原

General processes of slope evolution are explained by the 3 development models, but none of these is appropriate for all slopes, 2 slope form models have been introduced.

坡面發育的一般過程可用3個發展模型作解釋, 但並無一個可以用於解釋所有坡面情況, 2個坡面形態模型便被提出以作輔助。

Slope profile

l 4 simple slope profile: straight, convex, concave & concave-convex slope

l 4個簡單的坡面剖面: 垂直, 凸坡, 凹坡及凹凸坡

l most likely they are found on the same slope at different part

l 通常都在同一個坡面的不同部分可被發現