Post-drift studies and Convectional Current Theory

Older floors are cooler and have had more time for sediment accumulation. In exams, connect low heat and thick sediments with old ocean floor.

Iron-bearing minerals in basalt record Earth's magnetic direction during cooling. In exams, treat basalt as a magnetic record.

Wegener emphasized drifting continents, while sea-floor spreading explained ocean-floor creation and movement. In exams, see them as stages of development, not opposites.

Unordered and asymmetrical stripes would not prove systematic spreading. In exams, consider symmetry and order as the key conditions.

At divergent boundaries, mantle rises and partially melts to form magma. In exams, link ridge volcanism with mantle upwelling.

Spreading at the Mid-Atlantic Ridge separates plates on both sides. In exams, use the Atlantic as an example of active spreading.

Convergence and subduction are widespread along Pacific margins, so trenches occur there. In exams, link the Pacific with destructive boundaries.

Sea-floor spreading proved Earth's dynamism through magnetism, age, and heat-flow evidence. In exams, treat it as a foundation of modern plate tectonics.

Convection currents explain movement of energy and material in the mantle. In exams, treat them as an internal process related to plate motion.

New crust forms at divergent boundaries, especially at mid-oceanic ridges. In exams, link construction with spreading.

Old oceanic crust becomes cooler and denser, allowing subduction. In exams, connect density with destructive boundaries.

Matching margins were clues, but ocean-floor ages and magnetic stripes were direct measurements. In exams, distinguish clues from measurable evidence.

The stripes record Earth's magnetic reversals and successive formation of new crust. In exams, understand this as a marine magnetic time sequence.

Distance and age can be used to estimate average spreading rate. In exams, remember the distance-age relation for rate.

A difference between creation and destruction rates can widen or narrow an ocean. In exams, link ocean-basin shape with plate balance.

Holmes suggested that mantle movement could drive continental motion. In exams, remember it as a causal mechanism.

Plate tectonics explained the movement of both continents and ocean floors within one framework. In exams, treat plate tectonics as the broader explanation.

New crust forms at ridges, while old crust is destroyed at trenches. In exams, remember this construction-destruction pair.

Increasing sediment and rock age with distance indicates spreading. In exams, link age increase with distance from the ridge.

With subduction, material melts to form magma, which can create island arcs. In exams, connect trenches and island arcs within the subduction system.

This concept showed ocean floors as regions of active plate boundaries. In exams, view oceans as dynamic geological systems.

Together, these three strengthen the explanation of plate motion in post-drift studies. In exams, remember this trio as force, process, and evidence.

Modern explanation understands plate motion through the combined effects of mantle convection, slab pull, and ridge push. In exams, remember the combined mechanism rather than only one force.

Ocean-floor studies identified features such as mid-oceanic ridges and trenches. For exams, connect this with evidence for plate tectonics.

Convection currents are considered to occur in the mantle due to temperature differences. Remember the mantle as the base of plate movement in exams.