Question

describe the nature of deep weathered layers in tropical regions

Answer 1

 Shetland, deep weathering of bedrock is not widespread, a reflection of the efficiency of glacial erosion. Three contrasting styles of alteration occur: kaolinitic alteration zones in igneous and metamorphic rocks, inter-basaltic weathering of Devonian age in the volcanic rocks of Papa Stour and the more widespread sandy weathering.

The kaolinitic weathering is associated with zones of hydrothermal alteration, where circulating hot groundwater have altered rock minerals deep below ground as igneous or metamorphic rocks cooled. The most accessible example lies in the Burn of Tactigill, east of Tresta (May and Phemister, 1968). Here the alteration zone is up to 30m wide and follows the line of a NNE-SSW fault. The mica schist is altered to a white kaolinite, with subsidiary illite and mica. The quartz is corroded and the sand fraction contains rutile (Coque-Delhuille and Veyret, 1988). A similar deposit occurs at Moo Wick on Fetlar.

Answer 2

Answer:

"Deep weathering" is most common in the "tropical regions".  

The following reasons can explain the deep weathering in the tropical regions.

• Abundant vegetation provides humid acids as they decline.  

• Abundant rainfall percolates through the soil, increasing soil moisture to accelerate deep weathering.

•  High temperatures accelerate chemical reaction rates

• Dense vegetation maintains the weathered mantle.  

• The occurrence of faulty rocks offers fractures that acids can pass through already produced.