SSC CGL Geography · Oceanography
Tides, Salinity and Coral Reefs
Why the sea rises and falls twice a day, spring and neap tides, how salt sets the layers of the sea, and India's coral reefs and why corals bleach.
Why this matters
Seven questions in the bank: two from the 2023 shifts, three from the 2024 shifts and two from the 2025 shifts. Each is a single fact about tides, salt or corals, so one short list covers them.
Concept 1 of 2: Tides and salinity
Definition
Tides:
- The pull of the moon and the sun makes most coasts rise and fall twice a day.
- Spring tides (highest) come when the sun, moon and Earth are in a line, at new and full moon.
- Neap tides, with the smallest range, come when the two pulls work at right angles as seen from the Earth.
Salinity:
- Less salty water is lighter, so it lies above saltier water.
- The open ocean holds about 35 grams of salt per litre; the Dead Sea about ten times as much, which is why people float in it.
| Tide | Sun and moon |
|---|---|
| Spring tide | In a line with the Earth |
| Neap tide | At right angles |
Practise this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 1 · Oceanography · Tides, Salinity and Coral Reefs
Neap is right angles, not a line
Concept 2 of 2: Coral reefs
Definition
The facts:
- India's four main coral reef areas: the Gulf of Kutch, the Gulf of Mannar, Lakshadweep, and the Andaman and Nicobar islands.
- Coral bleaching happens when warmer water makes corals throw out the algae that live in them. The main cause is a rise in sea temperature brought about by people.
| Fact | Answer |
|---|---|
| Main cause of bleaching | Rising sea temperatureQ |
| Reef areas of India | Gulf of Kutch, Gulf of Mannar, Lakshadweep, Andaman and Nicobar |
Practise this conceptself-check · 2 quick reps
The same idea in a real exam question:
Example 2 · Oceanography · Tides, Salinity and Coral Reefs
Bleaching is about heat
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (2)
Tides and salinity2 rows
| Tide | Sun and moon |
|---|---|
| Spring tide | In a line with the Earth |
| Neap tide | At right angles |
Coral reefs2 rows
| Fact | Answer |
|---|---|
| Main cause of bleaching | Rising sea temperatureQ |
| Reef areas of India | Gulf of Kutch, Gulf of Mannar, Lakshadweep, Andaman and Nicobar |
Watch out for (2)
- Neap is right angles, not a line→ Tides and salinity
- Bleaching is about heat→ Coral reefs
Test yourself on a real paper
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