What is magnetic polarity and how is it recorded?

What is magnetic polarity and how is it recorded?

When the field points toward the north magnetic pole, as it does today, the field and the rocks that record it have “normal” polarity. When the field points toward the south magnetic pole, opposite of its current behavior, the field and the rocks that record it have “reversed” polarity.

What is the polarity of Earth’s magnetic field?

In the Northern Hemisphere, your compass needle points North, but if you think about it for a moment, you will discover that the magnetic pole in the Earth’s Northern Hemisphere has to be a South polarity.

How can the clues about the Earth’s magnetic field reversals recorded east and west of the mid-ocean ridge be used to support sea floor spreading?

Seafloor Age Brunhes normal – present to 730,000 years ago. Matuyama reverse – 730,000 years ago to 2.48 million years ago. Gauss normal – 2.48 to 3.4 million years ago. Gilbert reverse – 3.4 to 5.3 million years ago.

How does magnetic polarity reveal the age of a piece of sea floor?

Rocks of normal and reversed polarity are found in stripes symmetrically about the mid-ocean ridge axis. The age of seafloor rocks increases from the ridge crest to rocks the farthest from the ridges.

What is magnetic polarity?

Polarity is a term used in electricity, magnetism, and electronic signaling. Suppose there is a constant voltage , also called an electric potential or electromotive force (EMF), between two objects or points. In such a situation, one of the objects or points (poles) has more electrons than the other.

How often does Earth’s magnetic field switch polarity?

These reversals are random with no apparent periodicity to their occurrence. They can happen as often as every 10 thousand years or so and as infrequently as every 50 million years or more. The last reversal was about 780,000 years ago.

How are magnetic reversals recorded in the rock record?

A reversal occurs only when the magnetic field orientation changes to the opposite direction. Past reversals of the magnetic field are recorded in the rocks. When the rock finally solidifies, these minerals “lock in” the magnetic field as so many tiny compasses. Sedimentary rocks also have a magnetic record.

How is polarity defined?

1 : the quality or condition inherent in a body that exhibits opposite properties or powers in opposite parts or directions or that exhibits contrasted properties or powers in contrasted parts or directions : the condition of having poles.

How are the polarity of the magnet and the polarity of the voltage related explain?

The magnitude of the voltage is proportional to the rate of change of magnetic flux in the coil, so that moving the magnet in faster will produce a greater voltage. The polarity of the voltage is such that it opposes the change that produces it, so pulling the magnet out will produce a voltage of the opposite polarity.

Does the earth switch polarity?

This field changes over time, and also behaves differently in different parts of the world. The field can even change polarity completely, with the magnetic north and south poles switching places. This is called a reversal and last happened 780,000 years ago.

How is the polarity of the earth’s magnetic field recorded?

The polarity of the Earth’s magnetic field is recorded in igneous rocks, and reversals of the field are thus detectable as “stripes” centered on mid-ocean ridges where the sea floor is spreading, while the stability of the geomagnetic poles between reversals has allowed paleomagnetism to track the past motion of continents.

How are magnetic anomalies recorded on the sea floor?

As it cools it becomes permanently magnetized in the direction of the Earth’s magnetic field. Magnetometers, towed near the sea surface behind research ships or mounted on submarines like Alvin, measure the magnetic anomalies or “wiggles” that record the changes in magnetization of the volcanic sea floor.

How does the earth’s magnetic field affect new crust?

As new crust forms at mid-ocean ridges, tiny grains of magnetic minerals align themselves according to the Earth’s magnetic field. As the rock cools, the alignment of these grains becomes permanent and provides evidence of the polarity of the Earth’s magnetic field at the time of their formation.

How are polarity reversals of mid ocean ridges recorded?

A polarity reversal means that the magnetic North flips to where we know the South Pole is. At the mid-ocean ridge spreading axis, these flips in the direction of the Earth’s magnetic field are recorded in the magnetization of the lava. This creates a symmetrical pattern of magnetic stripes of opposite polarity on either side of mid-ocean ridges.