Post-drift studies and Convectional Current Theory

Correct answer: A. Explanation of the force moving continents

Holmes considered mantle convection currents as a possible driving force for continental movement. Exam tip: link Wegener's weakness with driving force.

Correct answer: B. Decay of radioactive elements

Radioactive decay produces internal heat that powers convection. Exam tip: remember internal heat and mantle movement together.

Correct answer: C. Difference in temperature and density

Hot material becomes lighter and rises, while cooler material becomes denser and sinks. Exam tip: understand convection through temperature and density differences.

Correct answer: D. Divergent boundary

Rising material creates spreading, causing plates to move apart. Exam tip: connect rising currents with mid-oceanic ridges.

Correct answer: A. Subduction

Cooler and denser plate or material sinks, which is linked with subduction. Exam tip: connect descending currents with oceanic trenches.

Correct answer: B. They were too weak to move continents

Later scientists found these forces too weak to move huge continental masses. Exam tip: link the criticism with the magnitude of force.

Correct answer: C. Systematic distribution of mid-oceanic ridges and trenches

Ridges and trenches in ocean floor relief became indicators of plate movement. Exam tip: treat ocean-floor evidence as a base of new understanding.

Correct answer: D. It behaves plastically and flow-like over long periods

The mantle does not behave like a rigid solid; over long periods it can flow slowly. Exam tip: understanding the time scale is important.

Correct answer: A. Formation of new oceanic crust

Rising material can cool and form new oceanic crust. Exam tip: connect it with seafloor spreading.

Correct answer: B. Seafloor spreading occurs

Symmetrical magnetic stripes prove spreading of new crust on both sides. Exam tip: link magnetic stripes with seafloor spreading.

Correct answer: C. They can pull the crust apart

Upper currents in opposite directions can create tension and spreading in the crust. Exam tip: study direction with boundary type.

Correct answer: D. Driving mechanism of plate movement

The upper convection current can exert frictional drag at the base of a plate. Exam tip: understand it as basal drag.

Correct answer: A. It suggested not only evidence but also a possible mechanism

The direct answer is Option A. Wegener’s continental-drift theory used evidence such as matching coastlines, similar fossils and related rocks, but it did not satisfactorily explain what force moved the continents. The convectional-current theory was more advanced because it suggested a possible physical mechanism: heat inside Earth could produce convection currents in the mantle, helping drive movement. Option A is therefore correct. Option B is wrong because later theories did not reject fossil evidence; fossils remained important support. Option C is absurd because Earth was not considered flat. Option D is wrong because the theory concerned movement, not fixed oceans. Exam cue: Wegener provided evidence; convection theory tried to explain the driving process.

Correct answer: B. They are linked with plate boundaries

Earthquakes and volcanoes mostly occur along active plate boundaries. Exam tip: treat narrow belts as indicators of plate boundaries.

Correct answer: C. Seafloor spreading

New crust forms at ridges and gradually spreads on both sides. Exam tip: understand age pattern as evidence of spreading.

Correct answer: D. Convection intensity may decrease

Convection is powered by internal heat, so reduced heat may weaken the motion. Exam tip: connect cause and effect directly.

Correct answer: A. After reaching upward, it cools and moves laterally

After rising, the material cools and spreads horizontally. Exam tip: link it with the spreading process at ridge zones.

Correct answer: B. Because ridges, trenches, and signs of new crust were found there

The ocean floor gave new evidence for Earth's dynamism. Exam tip: connect ocean-floor study with the development of plate tectonics.

Correct answer: C. In the broad material of the mantle

Convection is related to large-scale movement of mantle material. Exam tip: see it as a global, not local, process.

Correct answer: C. Currents converging near the surface from both sides

Converging currents can promote convergence and subduction. Exam tip: identify boundary type from flow direction.

Correct answer: D. Because it gave the idea of crustal movement driven by internal heat

Holmes linked internal heat and material movement with surface mobility. Exam tip: treat it as background to plate tectonics.

Correct answer: A. Internal process moving the broken landmasses

Holmes' contribution was not evidence for Pangaea but a possible mechanism of movement. Exam tip: separate the contributions of theories.

Correct answer: B. Study of ocean floor and seismic activity

Deep earthquakes and plate sinking signs occur near trenches. Exam tip: connect trenches with convergent boundaries.

Correct answer: C. By making the crust dynamic through heat and material movement

Internal heat creates mantle motion and may cause stress or spreading in the crust. Exam tip: understand the difference between internal and external processes.

Correct answer: D. New crust spread away from the ridge on both sides

Symmetry of magnetic stripes is strong evidence of seafloor spreading. Exam tip: link the word symmetry with spreading.