Indian Geography
🔒 Log in to trackMonsoon, local winds and soils
🔒 Log in to trackIndia has a tropical monsoon climate. The south-west monsoon reaches Kerala around 1 June. Winds, pre-monsoon showers and soil types each have a place, a crop and a cause that exams ask about.
Why India has a monsoon
The whole year turns on a seasonal reversal of winds. In summer the land heats up and draws in moist ocean winds. This is the south-west (SW) monsoon.
- It normally strikes the Kerala coast around 1 June. This is called the "burst" of the monsoon.
- It normally covers the whole country by about mid-July.
- By mid-September it starts to withdraw from the north-west.
It has two branches:
- Arabian Sea branch: gives very heavy rain on the windward side of the Western Ghats.
- Bay of Bengal branch: goes up the Ganga plain into the north-east.
Where rain falls and where it does not
The windward side of the Western Ghats (Mumbai, Konkan, Kerala) gets drenched. The leeward side (Pune, interior Karnataka, Marathwada) lies in the rain shadow.
- Mawsynram and Cherrapunji (Sohra) in Meghalaya's Khasi hills record some of the highest rainfall on Earth.
- West Rajasthan (Jaisalmer) is the driest.
- A long dry spell inside the season is a break in the monsoon.
- El Nino is a warming of the eastern Pacific. It is linked with weaker Indian monsoons.
Retreating monsoon and local winds
In October the monsoon winds leave. Hot, humid days of this month are called October heat. The retreating winds pick up moisture from the Bay of Bengal. They give October-December rain to the Tamil Nadu (Coromandel) coast. This is the north-east (NE) monsoon, Tamil Nadu's main rain.
| Name | Region | Nature or use |
|---|---|---|
| Loo | North Indian plains | Hot, dry summer wind |
| Mango showers | Kerala, Karnataka coast | Help mangoes ripen |
| Blossom showers | Karnataka | Help coffee flower |
| Kalbaisakhi / Nor'westers | West Bengal, Assam | Evening thunderstorms; help tea and jute; Bordoichila in Assam |
| Western disturbances | Punjab, Haryana, west UP, J&K | Winter rain from the Mediterranean area; vital for rabi wheat |
Tip: Match the shower to the crop. Mango showers help mango. Blossom showers help coffee. Kalbaisakhi helps tea.
Soils of India
ICAR recognises 8 soil groups.
| Soil | Where | Key facts |
|---|---|---|
| Alluvial | Northern plains, deltas | Most widespread (about 40% of area); khadar new and fertile; bhangar old with kankar; rice, wheat, sugarcane |
| Black (Regur) | Deccan trap: Maharashtra, Gujarat, MP | From basalt; holds moisture; "self-ploughing" cracks; cotton |
| Red and yellow | TN, Karnataka, Odisha, Chhattisgarh | Red from iron oxide; sandy; poor in humus |
| Laterite | Western Ghats, Kerala, Odisha hills, NE | Formed by leaching in heat and heavy rain; hardens like brick (Latin later); tea, coffee, cashew after manuring |
| Arid | West Rajasthan | Sandy, saline, calcium (kankar) layers |
| Saline / alkaline | Dry areas; over-irrigated Punjab-Haryana | Reh, kallar, usar; reclaimed with gypsum |
| Peaty / marshy | Kerala (kari), Sundarbans | High humus, black, heavy |
| Forest / mountain | Himalayan slopes | Rich humus, acidic |
Black soil is rich in lime, iron, magnesium and potash. It is poor in nitrogen, phosphorus and humus.
Watch: Laterite is not naturally fertile. Leaching washes its nutrients away.
Soil erosion and its cure
- Gully erosion: running water cuts the land into bare ravines. The Chambal badlands are the example.
- Sheet erosion: the topsoil layer is removed evenly.
- Wind erosion: open land in dry areas loses soil.
Remedies: contour ploughing, terrace farming, strip cropping, shelter belts of trees, afforestation.
Question types you will see
Each type: how to recognise it, the method step by step, and one question to try.
SW monsoon: onset, branches and withdrawal
When and where the monsoon strikes Kerala, its two branches, when it covers the country, or when it starts withdrawing.
Onset: about 1 June on the Kerala coast.
Coverage: most of India by mid-July.
Branches: Arabian Sea (Western Ghats) and Bay of Bengal (north-east, Ganga plain).
Withdrawal starts from the north-west around mid-September.
The monsoon follows a fixed calendar of four dates.
The south-west monsoon normally sets in over the Kerala coast around which date?
Show solutionHide solution
The burst happens on the Kerala coast.
The usual date is 1 June.
It then covers the country by mid-July.
1 June
Rainfall distribution, rain shadow and extremes
'Which region gets the highest or lowest rainfall?', 'Why is Pune dry?', 'rain shadow of the Western Ghats', 'Mawsynram is in which state?'
Windward Ghats (Konkan, Kerala, Mumbai): very heavy rain.
Leeward side (Pune, interior Karnataka, Marathwada): rain shadow.
Wettest: Mawsynram and Cherrapunji (Sohra), Meghalaya. Driest: west Rajasthan.
Tamil Nadu's coast is dry in June-September; its main rain comes later.
Slope direction decides who gets rain.
Mawsynram, one of the rainiest places on Earth, lies in which state?
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It is in the Khasi hills.
The Khasi hills are in Meghalaya.
Meghalaya. Cherrapunji (Sohra) is the other wet station nearby.
Retreating monsoon, October heat and local winds
'Kalbaisakhi is associated with', 'mango showers help which crop', 'October heat', 'which wind brings winter rain to Punjab'.
October: winds retreat; hot and humid days are October heat.
Oct-Dec rain on the Tamil Nadu coast is the NE monsoon.
Showers by crop: mango, blossom (coffee), Kalbaisakhi (tea, jute; Bordoichila in Assam).
Winter rain in the north-west: western disturbances.
Each wind or shower has one region and one crop.
Kalbaisakhi thunderstorms, which help tea and jute, occur mainly in which region?
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Kalbaisakhi is a Nor'wester.
It is in West Bengal and Assam.
It comes in spring (March to May).
West Bengal and Assam. In Assam the same season brings the Bordoichila winds.
Soil type, properties, formation and crops
'Regur soil is best for', 'which soil is formed by leaching', 'black soil is deficient in', 'khadar and bhangar are types of'.
Match soil to origin: alluvial (river deposits), black (basalt), red (iron oxide), laterite (leaching).
Black soil is rich in lime, iron, magnesium, potash and poor in N, P, humus.
Saline and alkaline soil (reh, usar) is reclaimed with gypsum.
Every soil has one cause and one crop, so match those two.
Black (regur) soil is well known for being deficient in which nutrients?
Show solutionHide solution
Recall the poor list: N, P, H.
It holds moisture well and suits cotton.
Nitrogen, phosphorus and humus
Soil erosion and conservation
'Ravines of the Chambal are an example of', 'contour ploughing is used for', 'sheet erosion means'.
Gully erosion (running water) makes ravines.
Sheet erosion removes topsoil evenly.
Wind erosion strips dry open land.
Remedies: contour ploughing, terrace farming, strip cropping, shelter belts, afforestation.
The type of erosion is named by how the soil is lost.
The gullied badlands along the Chambal river are a classic example of what?
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Running water cuts deep channels.
This makes ravines.
Gully erosion
Soil and region matching
'Laterite soil is found in', 'peaty soil is found in', 'arid soil is found in', or a match-the-column of soils and regions.
Alluvial: northern plains and deltas.
Black: Maharashtra, Gujarat, MP.
Red and yellow: TN, Karnataka, Odisha, Chhattisgarh.
Laterite: Western Ghats, Kerala, Odisha hills, NE.
Arid: west Rajasthan. Peaty: Kerala (kari), Sundarbans.
Each soil has a home region, and a few regions repeat.
Which soil is found in the Deccan trap region of Maharashtra, Gujarat and MP?
Show solutionHide solution
The Deccan trap is made of basalt.
Soil from basalt is black soil.
Black (regur) soil
Shortcuts that save time
Rich in Lime, Iron, Magnesium, Potash. Poor in Nitrogen, Phosphorus, Humus.
Black soil is generally deficient in which nutrient?
Show solutionHide solution
Recall the poor list: N, P, H.
Nitrogen is first on it.
Nitrogen (also phosphorus and organic matter)
Mango showers: mango, Kerala. Blossom showers: coffee, Karnataka. Kalbaisakhi: tea, jute, rice in Bengal and Assam. Western disturbances: rabi wheat in the north-west.
Mistakes to avoid
Where most students lose marks on this subtopic.
Saying Tamil Nadu gets most rain from the south-west monsoon.
Its main rain is in October to December from the retreating (north-east) monsoon.
Blaming aluminium for the red colour of red soil.
The colour comes from iron oxide.
Treating laterite as naturally fertile.
It is leached and needs manure.
Treating the Chambal ravines as sheet erosion.
They are gully erosion by running water.
Reclaiming saline soil with lime or manure.
Saline and alkaline soil is treated with gypsum.
Quick revision
Read this the night before the exam.
SW monsoon hits Kerala about 1 June. Two branches: Arabian Sea and Bay of Bengal. It withdraws from the NW by mid-September.
Rain shadow lies on the leeward Ghats. Mawsynram is the wettest. Tamil Nadu's main rain is Oct-Dec.
Loo = summer, north India. Mango showers = Kerala. Blossom = coffee. Kalbaisakhi = Bengal and Assam.
Black soil: basalt, cotton, rich in LIMP, poor in N, P and humus.
Laterite forms by leaching and hardens like brick. Saline soil is treated with gypsum.
Alluvial is the most widespread soil. Gully erosion makes the Chambal ravines.
Practice: 19 questions
Sets of 10, mixed across the question types above. Every answer has a step-by-step explanation.
Topic test · 10 questions
Suggested time 4 min · wrong answers go to your mistake notebook automatically.