UPSC Mains 2020 GS Paper 1 Q4: model answer
Discuss the geophysical characteristics of Circum-Pacific Zone.
What the question wants
Describe the geophysical characteristics of the Circum-Pacific Zone.
How to structure it
Discuss the geophysical characteristics: features with reasons.
- Location
- Plate setting
- Volcanoes
- Earthquakes and tsunamis
- Landforms
How to think it through
The Ring of Fire is a 40,000-km horseshoe where the Pacific floor is being swallowed. Swallowing makes trenches; melting makes volcanoes; grinding makes earthquakes. Three verbs, one belt.
Model answer
The Circum-Pacific Zone, or Ring of Fire, is a horseshoe-shaped belt about 40,000 km long around the Pacific Ocean, from New Zealand through Indonesia, Japan, the Aleutians and down the Americas to Chile.
Geophysical characteristics
- Plate boundaries: mostly convergent; the Pacific, Nazca and other oceanic plates
subduct under continental and oceanic plates.
- Deep trenches: the Mariana Trench (about 11 km) is the deepest point on Earth.
- Volcanoes: about 75% of the world's active volcanoes, including Mount Fuji, Pinatubo and Mount St Helens.
- Earthquakes: about 90% of earthquakes, including the largest recorded, Chile 1960 (magnitude 9.5), and Japan 2011.
- Tsunamis: triggered by undersea quakes, as in Japan 2011.
- Fold mountains and island arcs: Andes, Rockies, Japan, Aleutians.
- Transform faults: the San Andreas Fault, where plates slide past each other.
- High heat flow: geothermal energy in New Zealand, Indonesia and the Philippines.
- Mineral wealth: copper in Chile and Peru, formed by subduction-related magma.
- Rapid crustal change: new land appears and disappears, as with volcanic islands off Japan.
The zone shows plate tectonics at its most active.
Draw: Pacific map with the horseshoe of volcanoes and trenches.
Keywords, cases and data to drop in
Ring of Fire, subduction, Mariana Trench, Benioff zone, island arc, San Andreas, Chile 1960.
Where most answers lose marks
- Writing only 'volcanoes and earthquakes'. Add trenches, arcs and plate types.
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Question text as printed in the official UPSC Civil Services (Main) question paper. The model answer is original Battle IAS work; use it to learn structure, not to memorise.
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