Question

Which of the following statements accurately describe summer stratification in temperate lakes?

1. Summer stratification is pronounced in temperate lakes due to the rapid mixing of water layers.
2. Temperate lakes retain well-defined temperature layers that do not mix rapidly during summer.
3. Tropical lakes exhibit pronounced summer stratification because their layers mix slowly.
4. Summer stratification is rare in deep tropical lakes.

• A. i, ii
• B. iii only
• C. All
• D. ii only

Answer 1

Answer:

D. ii only

• Thermal stratification is fairly pronounced during the summer seasons in most lakes of the temperate (cold) regions but is rare in lakes of tropical (hot) and subtropical regions where it occurs only in very deep lakes.

• This is because the rate of mixing of layers is very fast in case of tropical lakes whereas, the temperate lakes retain well defined layers showing different temperature.

• These layers do not mix rapidly. Therefore the temperate lakes exhibit clear stratification with respect to temperature

• In lakes the top one metre of the water surface directly absorbs around 90 per cent of the total solar radiation falling on it and is considerably more heated in the process.

• Consequently, the lower sub-surface layers receive progressively less radiation and remain relatively cool.