HOw can the magnetic orientation of rocks be used to trace the way a continent move as it drifted? (hint: Special techniques exist for determining the age of rocks) My little sister has this problem, and asked me and i have no idea. PLEASE HELP
2006-12-19 13:41:07 · 4 answers · asked by Preposterous 2 in Science & Mathematics ➔ Earth Sciences & Geology
As magma rises as lava and cools to form rocks, any magnetic minerals in the rock (eg magnetite and haematite) align themselves with the earth's magnetic field. When the rock is solidified this magnetism is 'frozen' in the rock to form a weak, permenant magnet.
The direction in which they point can be measured by a cryogenic magnetometer.
This magnetic orientation can then be used to find where, in relation to the rock, magnetic north was. This leads to different rocks in continets showing different magnetic norths. As there is only one the continent itself has moved. Different samples will be taken from throughout the continent and the magnetic orientation is tested to find where magnetic north was. The position of magnetic north is plotted on a map to show apparent polar wander.
2006-12-19 20:15:37 · answer #1 · answered by abby00uk 2 · 1⤊ 0⤋
Magnetic particles in a rock can orient themselves like compass needles with the earth's magnetic field, and unless reset by heat or something, essentially freeze that information in the rock record. They line up north-south (declination) relative to the ancient magnetic north -just like a compass needle. And they also tilt (inclination), like a balancing compass needle, depending on latitude--horizontal (zero tilt) near equator, steep downward tilt near the pole. So, if a continent has been rotated, then the old orientations won't be pointing towards the modern magnetic north. And, if a continent has moved north or south to get to its present position, the inclination (tilt) of magnetic particles in older rocks will be different from the inclination you would get from a compass at present latitudes.
If you examined the paleomagnetic orientations (declinations and inclinations) of rocks of different ages on a continent, you could develop an idea of the way in which it has moved north or south and the way in which it has rotated over millions of years.
2006-12-19 23:55:42 · answer #2 · answered by luka d 5 · 2⤊ 0⤋
At different position on earth, the rocks will be magnetized in different manners and direction. Thus when the continent moves, the rocks magnetism will slowly adjust to match the of the external world. The technique for age of rocks is still carbon 14 i believe.
2006-12-19 21:45:40 · answer #3 · answered by Alex M 2 · 1⤊ 3⤋
A magnet, no matter where it is will be stronger pointing to true north. As the continent drifts, it's position from true north can be measured over time by using the formula develop by pythageros many years ago in Greece: A square+B square=C square. An easier way to say it is if you know 2 sides of a triangle, the length of the third side can be computed.
2006-12-19 23:36:23 · answer #4 · answered by Anonymous · 1⤊ 3⤋