How do magnetic reversals provide evidence for sea-floor spreading?

Answer 1

The presence of magnetic domains of alternating orientation parallel to the plate boundaries.

Answer 2

Evidence for Seafloor Spreading: Magnetic Reversals

Some of the most important evidence of seafloor spreading comes from magnetic reversals recorded in the ocean floor. Throughout Earth's history, the north and south magnetic poles have changed places many times. When the poles change places, the polarity of Earth's magnetic poles changes, as shown in Figure 4. When Earth's magnetic poles change places, this change is called a magnetic reversal.

Figure 4 The polarity of Earth's magnetic field changes over time.

Magnetic Reversals and Seafloor Spreading

The molten rock at the mid ocean ridges contains tiny grains of magnetic minerals. These mineral grains contain iron and are like compasses. They align with the magnetic field of the Earth. When the molten rock cools, the record of these tiny compasses remains in the rock. This record is then carried slowly away from the spreading center of the ridge as seafloor spreading occurs.

As you can see in Figure 5, when the Earth's magnetic field reverses, the magnetic mineral grains align in the opposite direction. The new rock records the direction of the Earth's magnetic field. As the sea floor spreads away from a mid ocean ridge, it carries with it a record of magnetic reversals. This record of magnetic reversals was the final proof that seafloor spreading does occur.

Figure 5 Magnetic reversals in oceanic crust are shown as bands of light blue and dark blue oceanic crust. Light blue bands indicate normal polarity, and dark blue bands indicate reverse polarity.

Answer 3

The Earth's crust is broken into many slowly moving plates. Sea floor spreading occurs at the mid ocean ridge where two plates are moving away from each other. Magma rises up from below and cools to form new seafloor rock

Answer 4

Because magnetic indicators in the rock point to either the north or south pole in parallel stripes adjacent to each other on either side of the mid Atlantic ridge. As the magma cools from seafloor spreading the magnetic direction is frozen into the rock creating the aforementioned stripes.

Answer 5

Evidence of magnetic reversal events in the basaltic rock on either side of the oceanic ridge mirrors the other side, providing proof that the crust is being created in both directions from the ridge.

Answer 6

Magnetic reversals recorded in oceanic crust show symmetrical patterns on either side of mid-ocean ridges, supporting the idea of sea-floor spreading. As magma rises and solidifies at mid-ocean ridges, it preserves the orientation of the Earth's magnetic field at that time. When the magnetic field reverses, these alternating magnetic stripes are recorded in the oceanic crust, providing evidence for sea-floor spreading.

Answer 7

Iron minerals help the seafloor spread by supporting the earth's magnetic pull.

Answer 8

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