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| The North Pole is Moving! |
| Magnetic North isn't where
it used to be... USGS |
| < Back Did you know the North Pole (well, the magnetic one) is moving, and seems to be accelerating? Check out this map showing the locations of the Magnetic North Pole at various times in our past...
The accompanying figure shows the path of the North Magnetic Pole since its discovery in 1831 to the last observed position in 2001. During the last century the Pole has moved a remarkable 1100 km. What is more, since about 1970 the NMP has accelerated and is now moving at more than 40 km per year. If the NMP maintains its present speed and direction it will reach Siberia in about 50 years. Such an extrapolation is, however, tenuous. It is quite possible that the Pole will veer from its present course, and it is also possible that the pole will slow down sometime in the next half century.
The strength and direction of the Earth's magnetic field slowly change
with time – a phenomenon referred to as secular change or secular
variation. The cause of secular variation is related to the process by
which the magnetic field is generated. Secular change occurs everywhere on
Earth, but the magnitude of the change varies from place to place and also
with time.
The field has even completely collapsed and reversed innumerable times,
which have been recorded in the magnetic alignment of lava as it cooled.
(see the
USGS "Stripes" page for more info on this) One theory to explain
magnetic pole reversals is related to large meteorite impacts, which could
trigger ice ages. The movement of water from the oceans to high latitudes
would accelerate the rotation of the Earth, which would disrupt magmatic
convection cells into chaos. These may reverse when a new pattern is
established. Another theory is that the reversals are triggered by a
slight change the angular momentum of the earth as a direct result of the
impacts. These theories are challenged by the controversial Reversing
Earth Theory, which proposes that the entire crust could shift and reverse
the true poles in a matter of days, but that the molten core would remain
stationary, resulting in apparent magnetic reversal. The Sun would then
rise in the opposite direction. |
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'Only' an inch One inch of rain is more water than you'd think... its fairly simple to get the amount of water using math... you figure out how much water 1 inch over one acre would be, and then you multiply that by how many acres are in Seattle's city limits....One Acre-foot of water (one acre covered by 1 foot of water) contains about 326,000 gallons of water. 1 square mile consists of about 640 acres (US Bureau of Measurements) 1 inch of rain = (~326000 acre-ft/12) = ~27,200 gallons / acre Seattle Area: 91.5685 square miles (Seattle Engineering Dept) so... ~640 * 91.5685 * ~27,200 = 1,594,572,800 gallons I guess that explains why there's flooding and flow control problems with what seems like a small amount of rain! A BILLION AND A HALF gallons is quite a bit of water to control! with the concrete and asphalt, most of the water is run-off, and a majority of that spills, untreated, into the Puget Sound.
Added in 2003 |
