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Zorluk: ZorSoil Types, Distribution, and Soil Conservation in Nigeria

In the crystalline Basement Complex terrain of Southwestern Nigeria, soil characteristics vary systematically along a hillslope profile (soil catena). Arrange the following soil types/zones in the correct order from the hilltop (summit) down to the valley bottom.

  1. 1Shallow, gravelly lithosols formed on exposed rocky inselberg summits and steep crests.
  2. 2Deep, well-drained reddish-brown Ferruginous soils on stable upper pediment slopes.
  3. 3Medium-textured colluvial soils accumulated along gentle lower pediment slopes.
  4. 4Seasonally waterlogged, greyish hydromorphic clay soils (Fadama) in the valley depression.

Cevap

The correct catenary sequence from hill crest to valley bottom is: Shallow lithosols on crests → Deep reddish Ferruginous soils on upper slopes → Colluvial soils on lower pediment slopes → Hydromorphic clay soils (Fadama) on the valley floor.
In Nigerian Basement Complex landscapes, relief dictates drainage, soil depth, and moisture regimes along a catenary gradient. The sequence begins at the crest with shallow lithosols due to runoff, moves to well-drained deep Ferruginous soils on upper pediment slopes, transitions to colluvial deposits on lower slopes, and terminates in waterlogged hydromorphic clay soils in valley bottoms.

Adım Adım Çözüm

1
Identify the soil condition at the highest elevation (summit/crest)
Hill crests experience rapid erosion and high runoff, leaving shallow, rocky skeletal soils (lithosols).
Topographic position governs weathering duration and erosion rates along a catena.
2
Determine soil development on the upper pediment slope
Upper pediment slopes feature deep, well-aerated, reddish Ferruginous tropical soils.
Good drainage and slope stability favor deep profile development and iron oxide accumulation.
3
Trace soil particle movement to the lower pediment slope
Lower slopes collect hill-wash debris, producing colluvial soils of medium texture.
Overland flow and gravity transport colluvial material down to gentle lower gradients.
4
Identify the soil type occupying the valley depression
Valley floors accumulate drainage water, giving rise to waterlogged hydromorphic (Fadama) clay soils.
High water tables and anaerobic conditions cause gleying in low-lying alluvial depressions.

Anahtar Kavram

Soil Catena and Topographic Control on Nigerian Soil Distribution
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