Post-drift studies and Convectional Current Theory

Correct answer: A. Because Wegener gave evidence of movement but did not clearly explain sufficient force

Wegener's evidences were important but the driving force was weakly explained. Exam tip: separate evidence and mechanism.

Correct answer: A. It suggested a possible internal force for continental movement

Holmes linked mantle convection with movement of landmasses. Exam tip: treat it as a possible solution to Wegener's weakness.

Correct answer: A. Hot material becomes lighter and rises while cool material becomes heavier and sinks

Thermal difference creates density difference and starts a convection cycle. Exam tip: remember hot rises and cool sinks.

Correct answer: A. They can affect plates and large surface movements over geological time

Mantle movement is slow but effective over long time. Exam tip: remember the geological time scale.

Correct answer: A. It revealed features like ridges trenches and submarine mountain chains

Ocean-floor mapping helped understand the dynamism of Earth's surface. Exam tip: do not treat the ocean floor as flat.

Correct answer: A. Upwelling current may be linked with formation of new material at ridge zones

Upwelling material near ridges is linked with new ocean floor. Exam tip: understand ridges as spreading zones.

Correct answer: A. Because they may be related to sinking or subduction zones

Trenches are deep parts and may be linked with downward movement. Exam tip: remember trenches with sinking.

Correct answer: A. It showed that the ocean floor can also be dynamic

Seafloor spreading challenged the idea of a fixed ocean floor. Exam tip: treat it as post-drift evidence.

Correct answer: A. Decay of radioactive elements

Radioactive decay can generate heat inside Earth. Exam tip: treat internal heat as the basis of convection.

Correct answer: A. It can indicate that floor age increases away from ridges

Age of ocean floor helps understand direction and development of spreading. Exam tip: remember the relation between age and ridge.

Correct answer: A. Because both help identify active geological belts

Earthquakes and volcanoes are linked with active zones of Earth. Exam tip: also connect their distribution with plate boundaries.

Correct answer: A. A zone of cyclic current with rising and sinking motion

In a convection cell hot material rises and cool material sinks. Exam tip: understand it as a cycle.

Correct answer: A. It gave the idea of internal energy and mechanism for plate movement

Convection currents provided a way to link plate movement with mantle motion. Exam tip: understand it as background to plate tectonics.

Correct answer: A. The possibility of convection currents would decrease

Convection is movement caused by differences in temperature and density. In the mantle, warmer material tends to become less dense and move upward, while cooler, denser material tends to move downward. This continuous contrast can help produce convection currents. If the mantle had no thermal difference, this driving force would be greatly reduced, so the formation or strength of convection currents would decrease.

Option A is therefore the best answer. Option B gives the opposite effect, because removing a thermal contrast would not immediately make convection faster. Options C and D are also too extreme: the ocean floor would not simply disappear, and earthquakes would not necessarily stop completely. The question asks specifically about convection currents, so the direct effect of losing the temperature difference is reduced convection.

Correct answer: A. New ocean floor may form near ridges and spread on both sides

In seafloor spreading ridge zones are centers of formation and spreading. Exam tip: connect ridges with spreading.

Correct answer: A. Downward movement of older oceanic material

In subduction material may move from surface toward interior. Exam tip: remember trenches as sinking zones.

Correct answer: A. The ocean floor is completely flat and inactive

Direct answer: Option A, the idea that the ocean floor is completely flat and inactive. Ocean-floor ridges are long elevated underwater features, while trenches are deep narrow depressions. Their discovery showed that the sea floor has varied relief and is connected with geological activity. This evidence weakened the old oversimplified belief that the ocean floor was an unchanging, level surface. Option A is correct because ridges and trenches directly contradict “completely flat and inactive.” Option B is wrong because the presence of water over the ocean floor is an obvious condition, not an idea weakened by discovering landforms beneath it. Option C is wrong because rocks on continents are unrelated to the specific conclusion about ocean-floor relief. Option D is wrong because gravity is not challenged by the discovery of ridges and trenches. Reasoning: underwater features were observed; therefore the floor is not uniformly flat; geological processes must be considered. Memory cue: ridges rise and trenches sink, so the sea floor is not a flat sheet.

Correct answer: A. Because over long time it can behave like a slow flow

Mantle material may behave rigidly but can move slowly over geological time. Exam tip: understand the importance of long duration.

Correct answer: A. They linked continental movement with ocean-floor and mantle processes

Post-drift studies linked movement with a broader Earth system. Exam tip: write the relation between surface and interior.

Correct answer: A. Convection cycle

Direct answer: Option A, convection cycle. In convection theory, heating creates density differences. Warmer, less-dense material rises, while cooler, denser material descends. These two opposite movements are not separate unrelated events; together they complete a repeating circulation. That repeating circulation is called a convection cycle or convection cell. Option A is therefore correct. Option B, river delta, forms where a river deposits sediment, usually near its mouth; it is not produced by rising and sinking currents. Option C, glacial lake, is formed by ice-related erosion or melting and has no connection with this mechanism. Option D, desert dune, is a wind-shaped deposit of sand, not a heat-driven internal circulation. The reasoning is: heat causes rising, cooling causes sinking, and the two movements together make a cycle. Exam cue: rising plus descending material equals convection cycle.

Correct answer: A. It gave evidence about ocean-floor structure and processes

Marine geology helped understand the dynamism of the ocean floor. Exam tip: link it with ocean-floor study.

Correct answer: A. Currents formed by thermal differences in the mantle

Mantle currents can affect the plates lying above. Exam tip: understand influence from mantle to plate.

Correct answer: A. Internal energy can be linked with dynamic surface processes

Internal heat can link mantle and ocean-floor processes. Exam tip: write the relation between interior and surface.

Correct answer: A. Study of ocean-floor structure and age

Study of ocean floor was very useful in new understanding of continental movement. Exam tip: connect ocean-floor study with post-drift.

Correct answer: A. Because later ocean-floor and convection-current studies must also be mentioned

Post-drift topic explains developments after Wegener. Exam tip: write later evidence and mechanism.