The speed of continental drift

On May 2 1, 1, 984, NASA and NASA announced that British scientists had successfully measured the speed and direction of the earth's continent drifting slowly with the plate through geophysical satellites. The following measurement results were obtained:

Hawaii and North and South America approach each other at a speed of about 5. 1 cm every year;

Australia and North America separate at a speed of about 1 cm every year;

The Atlantic Ocean expands at a rate of about 1.5 cm every year.

Continental drift theory was put forward by German geographer Alfred Wegener in 19 10, and developed into plate tectonics theory in 1960s. According to this theory, the earth's surface consists of more than 10 continental and ocean plates, and the continents move with the plate drift. But for a long time, it has been impossible to produce direct evidence, because the measurement degree is extremely high and precise technology is needed-laser, radio astronomy, and atomic clock with trillions of precision.

According to the theory of plate tectonics, there is only one pan-continent on the earth, and plate movement began 250 million years ago. Pan-continent split at the junction of plates and began to drift very slowly, forming the present continent. Where continental plates collide, Himalayan mountains and other mountains are formed, and ocean plates dive below continental plates to form deep trenches. Plate subduction can be used to explain the repeated occurrence of huge earthquakes around the trench. Plate theory has been evaluated by various seabed data obtained from marine geology, but the direction and speed of continental drift have long lacked direct evidence.

1979, the United States launched a geophysical satellite with a measurement accuracy of one billionth of a second, which required huge and complicated calculations on the received data until 1984. Experiments also prove that birds can locate themselves in the constellation, and they have the ability to correct the seasonal changes of the constellation with their biological clocks, thus accurately determining the direction of progress. However, how can birds orient on cloudy days or when there is no sun or constellation? Some people put copper rods and magnetic rods on pigeons and found that both groups of pigeons could return smoothly on sunny days. But on cloudy days, only those with copper bars can return, and those with magnetic stripes lose their directional ability. It can be seen that geomagnetic orientation is a very reliable navigation system for birds.

In the village of Chaitingka in northeastern India, in August and September every year, on moonless nights, flocks of birds will fall around the lights in confusion. Feeding by villagers, over time, it became the famous "Death Valley in Chaitingka Village". Why is this happening? Dr. Sen Zhouda, an Indian bird expert, thinks that the answer to the strange thing in Chaitinka village lies in the local magnetic field. The reason is that there are abundant magnetic minerals nearby, and the magnetic activity is relatively strong in August and September. When the bird is disturbed by magnetic force, its "compass" will be confused, so it will fly uneasily and see the lights in the village dizzy, so it will pounce and fall to the ground.