Internal Earth Processes

Question 1: Discuss the two different types of magnetic poles.

Answer 1: There are two different types of magnetic poles: the magnetic poles and the geomagnetic poles. The magnetic poles are the two positions on the earth's surface where the magnetic field is entirely vertical. Another way of saying this is that the inclination of the earth's field is 90° at the North Magnetic Pole and -90° at the South Magnetic Pole. The earth's field is closely approximated by the field of a dipole positioned at the planet’s center. A dipole defines an axis. The two positions where the axis of the dipole that best fits the earth's field intersects the surface are called the North and South Geomagnetic Poles. If the earth's field were perfectly dipolar, the geomagnetic and magnetic poles would coincide. However, there are significant non-dipolar terms that cause the position of the two types of poles to be in different places.

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Question 2: Discuss and describe geomagnetic reversals and a geomagnetic excursion.

Answer 2: Based upon the study of lava flows of basalt throughout the world, it has been proposed that the earth's magnetic field reverses at intervals, ranging from tens of thousands to many millions of years, with an average interval of approximately 250,000 years. The last such event, called the Brunhes-Matuyama reversal, is theorized to have occurred some 780,000 years ago.There is no clear theory as to how the geomagnetic reversals might have occurred. Some scientists have produced models for the core of the earth wherein the magnetic field is only quasi-stable and the poles can spontaneously migrate from one orientation to the other over the course of a few hundred to a few thousand years. Other scientists propose that the geodynamo first turns itself off, either spontaneously or through some external action like a comet impact, and then restarts itself with the magnetic North pole pointing either north or south. External events are not likely to be routine causes of magnetic field reversals due to the lack of a correlation between the age of impact craters and the timing of reversals. Regardless of the cause, when magnetic North reappears in the opposite direction this is a reversal, whereas turning off and returning in the same direction is called a geomagnetic excursion.

Question 3: Discuss Newton and Einstein’s concepts of time.

Answer 3: From the age of Newton up until Einstein's profound reinterpretation of the physical concepts associated with time and space, time was considered to be absolute and to flow equably for all observers. The science of classical mechanics is based on this Newtonian idea of time.Einstein, in his special theory of relativity, postulated the constancy and finiteness of the speed of light for all observers. He showed that this postulate, together with a reasonable definition for what it means for two events to be simultaneous, requires that distances appear compressed and time intervals appear lengthened for events associated with objects in motion relative to an inertial observer.Einstein showed that if time and space is measured using electromagnetic phenomena (like light bouncing between mirrors) then due to the constancy of the speed of light, time and space become mathematically entangled together in a certain way (called Minkowski space) which in turn results in Lorentz transformation and in entanglement of all other important derivative physical quantities (like energy, momentum, mass, force, etc) in a certain 4-vectorial way.

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