Question

Magnetic reversals ____.

a.cause the movements of tectonic plates
b.confirmed the existence of subduction zones
c.provide strong evidence for seafloor spreading
d.have never occurred during geologic time

Answer 1

Magnetic reversals C. PROVIDE STRONG EVIDENCE FOR SEAFLOOR SPREADING.

Magnetic reversal is evident when the change in the Earth's magnetic field results in the magnetic north being aligned with the geographic south, and the magnetic south being aligned with the geographic north. It is also called geomagnetic reversal.

Magnetic reversals can occur in less than 100 years. It led to extinction events during the pre-historic times. Because the magnetic field is rapidly weakening, magnetic reversal may cause biblical floods.

Answer 2

The answer is C.

Seafloor spreading occurs at diverging tectonic plates boundaries (such as at mid-ocean ridges). When magma upwells to fill up the void, the iron in the magma aligns itself with earth’s magnetic fields before the magma cools to new crust. Since earth's north and south switch polarity over several centuries, the iron in newly formed crust will align opposite from the previously formed crust. These reversals can be used to prove that the bands of the new crust were laid at different times.