The orientation of a rocks magnetic field can tell you it's relative age.
The orientation of a rocks magnetic field can tell you it's relative age.
as you move away from an ocean ridge the rocks get older
Current passing through a wire in a magnetic field creates its own magnetic force in some direction. If you increase the current, force will be increased. If the direction of current is changed, direction of force will also be reversed. Direction of current is found by applying right hand rule.
Scientists follow the magnetic field lines of the earth and measure them regularly. They will compare the earlier measurements and note the changes in position of the magnetic axis and decide if it is changing or not! Also if there are sudden changes observed in magnetic field lines bec of solar flares from sun. Magnetism is an interesting chapter! learn more by watching and subscribing to this space @PhysicsFusion-sm3tr Hope this helps
You don't have to be a scientist to observe that fact. All you have to do is take any magnet and hang it up on a thread, so it's free to rotate and point wherever it wants to point. When you do that, you find that every magnet that's free to turn always turns to point at the same place ... a spot in far northern Canada. When you do this experiment with thousands of magnets in thousands of places all over the earth, and keep records of the direction that magnets point in various places, it all goes together to give a beautiful diagram of the earth's magnetic field. People who do a lot of traveling over long distances have used this fact for thousands of years to build a device that helps them find their way around the surface of the earth. The device is called the 'magnetic compass'.
The orientation of a rocks magnetic field can tell you it's relative age.
When rocks are formed, usually from lava flows, the magnetic orientation of them is set as they solidify. As these rocks are affected by continental drift and other factors such as earthquakes, the original magnetic orientation remains. Using the known strengths of the earth's magnetic field over time, it is possible to then tell where these rocks originally emerged.
The magnetic field periodically changes its orientation.
as you move away from an ocean ridge the rocks get older
You can't. The only thing the earth's magnetic field can tell you is the direction from where you are toward the earth's magnetic pole. That doesn't tell you anything about where you are.
The closer the lines the stronger the magnetic field.
Magnetic strips appear on the seafloor because it spreads apart, forming new rocks that have a magnetic properties.
Sediment cores taken from deep ocean floors tell scientists about magnetic polarity shifts which provides a direct link between magnetic field activity and the fossil record . The Earth's magnetic field determines the magnetization of lava as it is laid down on the ocean floor on either side of the Mid-Atlantic Rift where the North American and European continental plates are spreading apart . When the lava solidifies it then creates a record of the orientation of past magnetic fields much like a tape recorder records sound .
..get a compass?
They form by the cooling of ferrous rock at the time it transitions from a molten state to a solid state. The ferrous particles are trapped in the orientation of the earths current magnetic field. The earths magnetic field alternates every certain number of years (a huge number like 500,000 years.) Since rock will cool at different times alternating layers of rock can have a completely opposite magnetic orientation. They are useful because you can tell the relative age of the different layers of rock based on this evidence. Hope this helps. Very brief and crude explanation.
New oceanic crust is being created at the mid-ocean rift zones, a global divergent plate boundary system where uprising magma fills in the spaces being created by the pulling apart of plates. Part of the newly forming crust follows the direction of one plate, and part of the newly forming crust follows the direction of the other plate; therefore, the age of the rock created from the magma has a mirror image on either side of the rift. As new oceanic crust is continuously being formed at the mid-ocean ridges by upwelling molten rock, the direction of Earth's magnetic field is recorded in the rock by the orientation of magnetic minerals, which align themselves in the direction of the magnetic field before the rock completely crystallizes. Earth's magnetic field is known to change its orientation with frequency on a geologic time scale, thus a pattern of stripes of magnetic orientation is formed which can be detected with a magnetometer. The discovery of magnetic stripes on the seafloor have allowed researchers to provide additional proof that new crust is being created, and that magnetic reversals have occurred and will occur in the future. They tell us that over the course of thousands of years, Earth's polarity will reverse itself. The stripes are the magnetic "footprint" of Earth's shifting magnetic field.
During the Second World War, linear bands of positive and negative magnetic anomolies were found in the ocean floor, stretching for hundreds of miles, with an almost perfect symmetry either side of mid-ocean ridges. It was realised that these anomalies were evidence of periodic reversals of the earth's magnetic field. Molten basalt had been magnetised in the direction of the field and then cooled to 'fossilise' that direction. Each time the earth's magnetic field reversed, a stripe was added in the opposite direction.