Paleomagnetism: Earth’s Magnetic Field

Paleomagnetism

Paleomagnetism is the study of the Earth’s magnetic field preserved in rocks.

Paleomagnetism is the study of the record of earth’s magnetic field with the help of magnetic fields recorded in rocks, sediment, or archaeological materials or silt.
The polarity of the Earth’s magnetic field and magnetic field reversals are thus detectable by studying the rocks of different ages.
Rocks formed from underwater volcanic activity are mainly basaltic (low silica, iron-rich) that makes up most of the ocean floor.
Basalt contains magnetic minerals, and as the rock is solidifying, these minerals align themselves in the direction of the magnetic field.
This locks in a record of which way the magnetic field was positioned at the time.
Minerals that respond to a magnetic field can be found in some rocks and materials. As a result, when rocks are formed, the minerals align with the magnetic field, keeping them in place. When rocks record the position of the magnetic field, it’s known as rock magnetism.
Paleomagnetic studies of rocks have demonstrated that the orientation of the earth’s magnetic field has frequently alternated (geomagnetic reversal) over geologic time.
The earth’s magnetic properties, such as the magnetic north and south poles, are recorded in rocks during the rock formation period.
The study of magnetic characteristics of rocks from various periods can reveal the earth’s magnetic field’s shifting direction and the past location of tectonic plates.

Prediction of Future Behaviour of Earth’s Magnetic Field: We can predict the future behavior of Earth’s magnetic field by piecing together its history. Earth’s magnetic field has flipped and reversed in the past, according to rock records.
Source of Information on Earth’s Evolution:  Paleomagnetism, also known as fossil magnetism, is an important source of information about the Earth’s evolution throughout all of geological history.
Record of Strength and Direction of Earth’s Magnetic Field: Paleomagnetism provides a record of the strength and direction of the magnetic field of the planet. Numerous rocks have kept this record since the time of their formation
Acts as Proof for Plate Tectonics Theory: Paleomagnetism also supports plate tectonics hypotheses. They record the alignment of the magnetic fields surrounding oceanic ridges because the ocean floor is usually composed of basalt, an iron-rich rock containing minerals that align with the magnetic field.
Other Uses: The information has also proven essential for comprehending issues with local and regional tectonics, geodynamics, and the planet’s thermal history.

The majority of the ocean floor is made up of basaltic (low silica, iron-rich) rocks generated by underwater volcanic activity.
Basalt includes magnetic minerals, which align themselves in the direction of the magnetic field as the rock solidifies.
This records the direction in which the magnetic field was pointing at the time.
The orientation of the earth’s magnetic field has repeatedly alternated (geomagnetic reversal) over geologic time, according to paleomagnetic examinations of rocks.

Paleomagnetism led the revival of the continental drift hypothesis and its transformation into theories of Sea Floor Spreading and Plate Tectonics.
The regions that hold the unique record of earth’s magnetic field lie along the mid-ocean ridges where the sea floor is spreading.
On studying the paleomagnetic rocks on either side of the oceanic ridges, it is found that alternate magnetic rock stripes were flipped so that one stripe would be of normal polarity and the next, reversed.
Hence, paleomagnetic rocks (paleo: denoting rocks) on either side of the mid-ocean or submarine ridges provide the most important evidence to the concept of Sea Floor Spreading.
Magnetic field records also provide information on the past location of tectonic plates.

These oceanic ridges are boundaries where tectonic plates are diverging (moving apart).
The fissure or vent (in between the ridge) between the plates allowed the magma to rise and harden into a long narrow band of rock on either side of the vent.
Rising magma assumes the polarity of Earth’s geomagnetic field at the time before it solidifies on the oceanic crust.
As the conventional currents pull the oceanic plates apart, the solidified band of rock moves away from the vent (or ridge), and a new band of rock takes its place a few million years later when the magnetic field was reversed. This results in this magnetic striping where the adjacent rock bands have opposite polarities.
This process repeats over and over giving rise to a series of narrow parallel rock bands on either side of the ridge and alternating pattern of magnetic striping on the seafloor.

Paleomagnetism Explanation