Scientists discovered that the rock that makes up the ocean floor lies in a pattern of magnetized “stripes.” These stripes hold a record of reversals in Earth’s magnetic field. The rock of the ocean floor contains iron. The rock began as molten material that cooled and hardened.
What causes magnetic stripes on the seafloor?
When lava gets erupted at the mid-ocean ridge axis it cools and turns into hard rock. As it cools it becomes permanently magnetized in the direction of the Earth’s magnetic field. … This creates a symmetrical pattern of magnetic stripes of opposite polarity on either side of mid-ocean ridges.
Where are magnetic stripes found?
In most magnetic stripe cards, the magnetic stripe is contained in a plastic-like film. The magnetic stripe is located 0.223 inches (5.66 mm) from the edge of the card, and is 0.375 inches (9.52 mm) wide. The magnetic stripe contains three tracks, each 0.110 inches (2.79 mm) wide.
Why are magnetic polarity bands different widths?
The rock produced at the ridge will continue to have the same signature until the Earth’s field changes direction or intensity. The width of magnetic bands with a particular direction is proportional to both the rate of seafloor spreading and the length of time the magnetic field remains at a particular polarity.
What causes magnetic stripes on the seafloor quizlet?
Stripes of rock formed when Earth’s magnetic field pointed north alternate with stripes of rock that formed when the magnetic field pointed south. The alternating pattern is the same on both sides of a mid-ocean ridge.
Which magnetic stripe is the oldest How do you know?
The magnetic pole reverses from time to time. The north pole becomes the south pole, and the south pole becomes the north pole. Rocks of normal and reversed polarity are found in stripes symmetrically about the mid-ocean ridge axis. The seafloor is youngest at the ridge crest and oldest far away from the ridge crest.
What elements does a magnet attract?
Magnets are only attracted to special metals. Iron, cobalt and nickel are magnetic. Metals that have iron in them attract magnets well. Steel is one.
Do magnets damage credit cards?
Over time the magnetic strip on all credit cards will deteriorate. … Holding a magnet to the magnetic strip will indeed demagnetize a credit card, but the important factor here is the strength of the magnet. The larger the magnetic field, the more likely it is to effectively demagnetize the magnetic strip.
What process is responsible for creating magnetic changes along mid ocean ridges?
Is Earth’s polarity normal or reversed?
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 often do magnetic reversals occur?
‘ Reversals are the rule, not the exception. Earth has settled in the last 20 million years into a pattern of a pole reversal about every 200,000 to 300,000 years, although it has been more than twice that long since the last reversal.
What are the lines of evidence that support the plate movements?
Modern continents hold clues to their distant past. Evidence from fossils, glaciers, and complementary coastlines helps reveal how the plates once fit together. Fossils tell us when and where plants and animals once existed.
What are the 4 steps of seafloor spreading?
Terms in this set (7)
- Magma comes out of the rift valley.
- Magma cools to rock and hardens.
- Rock is pushed away as new rock is formed at MOR.
- Oceanic crust and continental crust meet at the trench.
- Oceanic crust bends down under the continental crust.
- Gravity pulls rock towards mantle.
- Rock melts to mantle.
What do ridges and rises have in common?
Ridges are associated with divergence, and rises are associated with convergence. Rises are associated with hotspots, and ridges result from seafloor spreading at divergent plate boundaries.
What is associated with reversed magnetic polarity?
A magnetic polarity reversal is a change of the earth’s magnetic field to the opposite polarity. … Rocks created along the oceanic spreading ridges commonly preserve this pattern of polarity reversals as they cool, and this pattern can be used to determine the rate of ocean ridge spreading.