Plate Tectonics is one of the most scoring and repeatedly asked topics in UPSC Geography. Questions often go beyond definitions and demand evidence-based explanations. A smart way to answer such questions is to classify evidences systematically and link older theories with modern scientific validation.
For effective revision, evidences of plate tectonics can be grouped under three broad heads:
- Evidences inherited from Continental Drift Theory
- Evidences based on tectonic concepts and processes
- Modern geophysical and remote sensing evidences
Let’s break them down.
Contents
1. Evidences from Continental Drift Theory (Wegener)
Although Wegener lacked a mechanism, his evidences remain valid under modern plate tectonics.
a) Jigsaw Fit of Continents
The eastern coast of South America fits remarkably with the western coast of Africa, especially Brazil fitting into the Gulf of Guinea. This geometric matching supports continental movement.
b) Geological (Rock) Evidence
- Matching gold deposits in Africa and South America
- Continuity of cratonic rocks between the Katanga (Africa) and Patagonia (South America) regions
These structural similarities suggest continents were once joined.
c) Fossil Evidence
Identical fossils found across now-separated continents:
- Glossopteris
- Mesosaurus
- Lystrosaurus
- Cynognathus
These organisms could not have crossed vast oceans, indicating earlier land continuity.
d) Paleoclimatic Evidence
- Glacial deposits in present-day tropical regions (India, Africa)
- Coal deposits in higher latitudes
This proves continents have shifted across climatic zones.
e) Mountain-Building (Scraping) Evidence
Though Wegener explained it imperfectly, modern tectonics confirms that sediment scraping during subduction forms fold mountains like the Andes and Rockies.
2. Conceptual Evidences from Plate Tectonics Theory
These evidences explain how plates move and interact.
a) Mantle Convection Currents
Proposed by Arthur Holmes, mantle convection provides the driving force behind plate movement, forming the backbone of tectonic theory.
b) Seafloor Spreading Evidence
Key indicators include:
- Mid-Oceanic Ridges
- Axial rift valleys
- Transform faults
- Increasing age of oceanic crust away from ridges
- Symmetrical magnetic reversal stripes
All confirm continuous creation and outward movement of oceanic crust.
c) Earthquake Distribution & Benioff Zone
- Earthquakes align along plate boundaries
- Deep-focus earthquakes occur along subduction zones
- Benioff Zone shows inclined seismic planes (≈35–40°), proving active subduction
d) Hotspot Volcanism
Linear volcanic chains like:
- Hawaiian Islands
- Emperor Seamount Chain
These record direction and speed of plate movement over stationary mantle plumes.
3. Modern Geophysical & Remote Sensing Evidences
a) Satellite-Based Plate Tracking
French SPOT satellite series and modern GPS systems track plate motion with high precision.
b) Instrument-Based Measurements
- Indian Plate moving northward at ~5 cm/year
- Accurate measurement of Pacific and Atlantic plate motions
These provide direct, measurable proof of plate tectonics.
How to Write This Answer in UPSC Mains
- Start with classification of evidences
- Use simple diagrams (Africa–South America fit, magnetic stripes, Benioff zone)
- Link old theories → modern confirmation
- Conclude with technological validation
This approach works well for 10, 15, and even 20-mark questions.
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FAQs
- #PlateTectonicsEvidence: What are the major evidences supporting plate tectonics?
- #ContinentalDriftTheory: How do Wegener’s evidences support modern plate tectonics?
- #SeafloorSpreading: Why is seafloor spreading considered strong evidence of plate movement?
- #BenioffZone: How does the Benioff Zone prove the existence of subduction?
