Mentors Comment:

• Quite a straightforward question and the demands are clearly stated. Diagram will fetch you more marks in geography-related questions. So don’t hesitate to use them here.
• Start with the intro which will be based on the first part of the question: What are landslides and how do they occur.
• It’s up to you on how to discuss the next part regarding Himalaya and w-ghats. Either you can combine the discussion or you can use the tabular form or discuss separately in two distinct subheadings. I have chosen the last option and discussed separately why landslides are frequent in Himalayas and less frequent in W-Ghats. It gives a distinct edge to the points and it is less confusing and more elaborative.

Answer:

Landslides are physical mass movement of soil, rocks and debris down the mountain slope because of heavy rainfall, earthquake, gravity and other factors. 

How do they occur:

The condition for the occurrence of landslides are 

• steep-sloped mountains, 
• the base of the huge mountains eroded by rivers or due to mining activities or erosion agents resulting in steep slopes, 
• loose rocks with the effect of gravity acting on them. 
• It becomes more dangerous when there is heavy rainfall, earthquakes, snowfall, solifluction. 
• Increased industrialization leading to climate change and weather disturbances
• Change in river flow due to the construction of dams, barriers, etc.
• Loose soil cover and sloping terrain.

Landslides are frequent in Himalayas because:

• Heavy snowfall in winter and melting in summer.
• This induces debris flow, which is carried in large quantities by numerous streams and rivers.
• Himalayas are made of sedimentary rocks that can easily be eroded. This aides landslides.
• Drifting of the Indian plate causes frequent earthquakes and resultant instability in the region.
• Man-made activities like grazing, construction and cultivation abet soil erosion and risks of landslides.
• The Himalayas not yet reached its isostatic equilibrium which destabilizes the slopes. It leads to landslides.
• Diurnal changes in temperature are much more in northern India than in southern slopes. This weakens the rocks and aids mass wasting.

Less frequent in W.Ghats because:

• The Western Ghats are eroded, denuded, aged, mature and worn out by exogenic forces. Moreover, they are far less in height. Hence landslide occurrence is rare.
• Less occurrence of earthquakes because they’re on a more stable part of the Indian plate.
• While steep slope on the western side with high rainfall creates ideal conditions for landslide but gentle eastern slope with low rainfall and rivers in the senile stage, counters the condition.
• W Ghats are older-block mountain therefore they are more stable now. Moving of Indian plates doesn’t affect them. 
• Small & swift-flowing streams of the western side and big matured rivers on the eastern side (like Krishna, Godavari, etc) cannot carry large amounts of debris.
• Western Ghats have lesser man-made interference as of now than what the Himalayas have faced.

Thus, the pristine and unique nature of Himalayas, steep and high mountain ranges and infrastructure projects have caused frequent landslides compared to Western Ghats.