Geography

Continental Drift Theory and its evidence

Q: Why would it be wrong to place seafloor spreading among Wegener's original evidences?

Because it was scientifically established after Wegener The correct answer is option A. The governing concept is the historical development of the continental-drift and plate-tectonic theories. Alfred Wegener proposed continental drift in 1912 and supported it with evidence such as the jigsaw fit of continents, matching fossils, continuity of rocks and related past climates. Seafloor spreading was not one of his original evidences because the ocean-floor mechanism and supporting magnetic data were developed and accepted later, especially through work by Harry Hess and subsequent oceanographic research. Options B, C and D either name unrelated processes or confuse a fossil clue with a later mechanism.

Q: Symmetrical magnetic stripe patterns on the ocean floor are related to which process?

Seafloor spreading The governing concept is seafloor spreading and its magnetic record. Basalt forms as magma rises and cools along a mid-ocean ridge. Iron-bearing minerals in the cooling rock align with Earth’s magnetic field, preserving the field’s polarity at that time. Because Earth’s polarity reverses periodically and new crust is added on both sides of the ridge, alternating magnetic bands occur in matching, symmetrical pairs. Option A is correct and provides evidence for spreading and plate movement. Continental-rise deposition, coastal marsh formation and river-valley erosion cannot create parallel ocean-wide magnetic stripes, so B, C and D are incorrect.

In Class 11 Geography, this topic explains the Continental Drift Theory within the chapter “Distribution of Oceans and Continents.” Students learn Alfred Wegener’s idea that the continents were once joined as Pangaea and gradually moved apart. They examine evidence such as the matching shapes of coastlines, similar fossils, continuous rock formations, mountain belts, and past glacial deposits found on continents now far apart. The topic also introduces the theory’s limitations and its importance in the later development of plate tectonics.

Hard · Level 7 · 2 questions

Practice questions

01Why would it be wrong to place seafloor spreading among Wegener's original evidences?

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Answer and explanation

Correct answer: A. Because it was scientifically established after Wegener

The correct answer is option A. The governing concept is the historical development of the continental-drift and plate-tectonic theories. Alfred Wegener proposed continental drift in 1912 and supported it with evidence such as the jigsaw fit of continents, matching fossils, continuity of rocks and related past climates. Seafloor spreading was not one of his original evidences because the ocean-floor mechanism and supporting magnetic data were developed and accepted later, especially through work by Harry Hess and subsequent oceanographic research. Options B, C and D either name unrelated processes or confuse a fossil clue with a later mechanism.

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02Symmetrical magnetic stripe patterns on the ocean floor are related to which process?

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Answer and explanation

Correct answer: A. Seafloor spreading

The governing concept is seafloor spreading and its magnetic record. Basalt forms as magma rises and cools along a mid-ocean ridge. Iron-bearing minerals in the cooling rock align with Earth’s magnetic field, preserving the field’s polarity at that time. Because Earth’s polarity reverses periodically and new crust is added on both sides of the ridge, alternating magnetic bands occur in matching, symmetrical pairs. Option A is correct and provides evidence for spreading and plate movement. Continental-rise deposition, coastal marsh formation and river-valley erosion cannot create parallel ocean-wide magnetic stripes, so B, C and D are incorrect.