For one thing, the fact that the earth has a north magnetic pole and a south magnetic pole enable compasses to work properly. Even more important, the magnetic field generated between these poles is so powerful that it acts like a shield to deflect incoming ionized solar winds.
Without it, our atmosphere (particularly the ozone layer) would over time be stripped away by the charged particles being emitted by the sun in the solar wind.
But what is the origin of earth's vital magnetic field?
One widely-accepted theory is that the motion of the liquid outer core creates a dynamo which generates our planet's magnetic field.
However, in the past few decades, scientists have confirmed evidence which suggests that the inner core may actually be the source of the magnetic field. This webpage from the Pittsburgh Supercomputing Center entitled "Crystal at the Center of the Earth" explains that data seems to suggest that the earth's solid inner core may actually be strongly anisotropic -- that it is directionally oriented such that waves passing through it behave differently when encountering the core along different axes.
Wood is anisotropic: its grains are aligned such that splitting wood is easier when force acts along the axis of the wood parallel to the grain, rather than perpendicular to the grain. Crystals are also anisotropic: light passing through a crystal will behave differently depending on the direction that it encounters the crystal.
In the 1980s, scientists began to notice that seismic waves (caused by earthquakes, as well as by powerful explosions and volcanic eruptions) appeared to travel through the earth at different rates depending on whether they went across the globe more parallel to earth's magnetic axis or whether they went across the globe more perpendicular to it. Traveling perpendicular to earth's axis, the seismic waves were noticeably slower -- taking an additional four seconds to pass through the earth than seismic waves that went north-to-south along the axis.
Earth scientists and physicists such as Doctors Jeroen Tromp of Harvard, Ronald Cohen of the Carnegie Institute of Washington, and Lars Stixrude of the Georgia Institute of Technology have suggested that the data suggests that the inner core may be organized as a crystal, as shown in the article linked above and as discussed in this article from 1995. The pressure at the inner core may be so great that iron and magnetite undergoes a phase shift which raises its melting temperature to the point that it can remain solid in the inner core, whereas it is liquid in the outer core (a theory explaining why this solid core may have formed with a north and south magnetic pole will follow below). Here is another webpage which summarizes the evidence that the inner core is anisotropic.
Dr. Walt Brown, the author of the hydroplate theory, explains that the extreme forces surrounding a catastrophic worldwide flood would explain these scientific findings regarding the earth's inner and outer core. In figure 95, found in note 37 on this page of his online book (which he makes available to all for no charge), he presents a simplified diagram showing the effect on the inner earth of the proposed upward springing of the floor of the Atlantic after the release of the floodwaters and the erosion of the sides of the continents, which removed weight above the basement rock that forms today's Atlantic floor (this event was discussed in some detail in this previous post). The caption accompanying the image at figure 95 explains:
The mass rising to fill in the blue region of the top cone (the new Atlantic floor) would, as a first approximation, equal the mass passing through the center of the earth. The rock in the yellow cone would experience extreme shearing stresses and deformations, so rock first melted as it approached (and was extruded through) the constriction at the center of the earth. (This is how the earth’s core, shown in red, began.) As the extruded rock melted, it also shrank, by about half, because it was far below the crossover depth. That, in turn, collapsed the deepest foundations on the Pacific side of the earth and produced more shearing deformations and melting immediately above. A runaway situation quickly developed which formed the ring of fire (shown in green), and produced a myriad of fractures in and below the Pacific plate [to see the different colored areas he is describing, visit figure 95 in his book].The extreme stresses he describes, triggered by the proposed global flood (an event supported by hundreds of geological pieces of evidence around the planet), could produce the melting required to form the inner and outer cores of the earth.
The alternate explanation, that earth was once molten and that it has been cooling from the outside over billions of years, has enormous problems. Dr. Brown discusses many of these problems here. Among them is the fact that, if earth had ever been completely melted, we would expect very heavy elements such as gold to have sunk towards the center of the earth, rather than being found in the crust as it is to this day.
Dr. Brown's theory explains why the extreme forces that caused the melting were concentrated around earth's core. He goes on to explain how the solid inner core formed, and why it has a magnetic orientation:
Crystals with the highest melting temperatures would not have melted. Those that were denser than the melt would have settled through the melt, initiating the crystalline growth of the solid inner core. This growth explains why a “Giant Crystal” is at the center of the earth and why earthquake waves travel much faster through the inner core in one direction than in the perpendicular direction. [See Endnote 47.] Crystals less dense than the melt would have floated to the top of the melt and pressed against the bottom of the mantle.
Also, in an inset entitled "The Origins of Earth's Powerful Magnetic Field" on this page (about 7/8ths of the way down the webpage), he provides this additional information:
A common and dense mineral that settled through the increasing melt in the inner earth was magnetite (Fe3O4). Its pressure naturally increased as it fell toward the center of the earth. This produced a phase change that increased the mineral’s melting temperature.51 Magnetite, which as its name implies is highly magnetic, retains its magnetic strength as long as its temperature remains slightly below its melting temperature.
As each magnetite crystal fell, the phase change prevented it from melting and allowed it to retain its magnetic strength. Each falling crystal oscillated like a tiny compass needle seeking the north magnetic pole. However, the viscous magma dampened those oscillations, so each crystal’s magnetic field quickly aligned with the earth’s existing magnetic field. That field grew in strength as each tiny magnet was added to the inner core.52
In summary, before the earth’s core began to form, trillions upon trillions of tiny magnetite crystals were somewhat randomly oriented inside the earth, so their magnetic strengths were self-canceling to some degree. When melting and gravitational settling ended, many of those crystals had fallen onto the inner core and aligned with the earth’s growing magnetic field. Thus, (1) the magnetic field increased greatly, and (2) crystals in the inner core are aligned parallel to the axis of the magnetic poles.
The evidence certainly appears to suggest that the material structure of earth's inner core (rather than the supposed "dynamo action" of the liquid outer core) may be the primary cause of earth's magnetic field. This appears to be further evidence which supports the hydroplate theory, and which the hydroplate theory can explain more satisfactorily than competing theories.
The fact that the anisotropic inner core alters the properties of seismic waves suggests that earth's powerful magnetic field may alter other waves as well. If it can impact earthquake waves (and scientists now believe the evidence is conclusive that it can), then is it too ridiculous to suggest that it can impact human beings and other creatures as well?
For example, in a post from September of last year, we examined arguments regarding whether the direction we point our heads when we sleep makes a difference. There is some evidence that other organisms possess powers of "magnetoception" -- the ability to detect magnetic fields. There is evidence that deer and cattle align with earth's magnetic field when they rest (unless in the vicinity of powerful electric lines), and that homing pigeons used magnetoception to supplement their other direction-finding instincts. Apparently, the actual organs used by animals to detect magnetic fields are still unknown.
We have also discussed allegations that ancient monuments, such as Avebury Henge, may indicate that our ancient predecessors understood more about magnetic fields than one would expect based on the conventional timeline of human history. This would harmonize with the fact that some of the ancient Hindu texts discussed in the post on sleep orientation indicate ancient awareness of this subject.
Clearly, the entire subject of earth's magnetic field -- its origin and our daily interaction with it -- is ripe for further exploration and discovery.