Geography Answer Writing Practice - Week 1 - Question 1
90 Days Geography Answer Writing Practice Question 1 for 04-Dec-2017
Instructions for Writing Answer1. Write your answers in the comment section.
2. Experts will provide their feedback in reply.
3. Model Answers will be uploaded on this page next day.
4. Rectify your mistakes and progress further.
5. All the Best.
04-Dec-2017 - Question 1
What is Base Level? Explain the types of base level. (2013)
Model AnswerJ W Powell was an American geologist who proposed the idea of Base Level. His concept of the base level has been used in geomorphology and hydrology to explain erosion by stream channels.
The base level is defined as the lowest level of land below which erosion cannot take place. The sea level is considered to be the grand base level below which the land cannot be eroded. We may also have a local or temporary purpose other base levels of erosion, which are the level of the bed of principal stream carrying the product of erosion.
There are three types of base level as explained by Powell
1 The grand base level is the sea level for subaerial erosion. Any change to the sea level can bring change to grand base level. E.g. Submergence or emergence of sea surface due to tectonic activity or isostatic changes.
2 The local or temporary base level. E.g. a channel may drain into a lake and lose its erosion capacity. For this channel, the level of the lake is its base level. Similarly, a river may encounter soft and hard bed rocks during its course. When passing from a soft rock bed to a hard rock bed, the river may face temporary base level in its path. Anthropogenic activity like the building of a dam in the path of the river can also act as a local base level for the river.
3 It is an imaginary sloping surface of a stream where erosion has practically ceased to take place. This idea was supported by Campbell. He explained that when the stream is in its old age the surface will constitute a peneplane. This peneplane will approach very close to base level.
Note: The model Answer is for only your reference purpose and is not the ideal answer for the question.
For Question 2 - Click Here