Did you feel that? Well probably not, but believe it or not, the Earth wobbles all the time as it spins on its axis — that imaginary line that passes through the North and South Poles. That wobble causes that “spin axis” to shift. Over a century it’s moved about 10 cm per year. Scientists now have a new handle on the causes of Earth’s Spin Axis Drift.
The boffins at NASA have been crunching away on data accumulated across the entire 20th century to identify three separate mechanisms that combine to cause the observed drift — 1) loss of mass in the global cryosphere (frozen regions), primarily in Greenland;, 2) glacial rebound, and 3) mantle convection.
Glacial rebound is the shifting of large land masses on the Earth’s surface in response to the loss of ice sheets. Not too long ago, in the last Ice Age, heavy glaciers covered a lot of the Earth’s surface. The whole of England is slowly rising in the west and sinking in the east. This can be observed by looking at castles like Harlech in Wales which were built on the coast, but are now miles inland. The fairy tale Avalon of King Arthur’s tales is speculated to actually have been Glastonbury Tor, which during that Dark Age period was actually an island, yet is now high and dry. This phenomenon can be observed in many places across Europe.
Mantle convection — another mouthful — is the action of the hot magma beneath the Earth’s tectonic plates, causing them to move. This magma heats and circulates like any heated fluid, behaving much like water boiling in a pot. This effect represents another large-scale shift in surface mass that contributes to the overall “wobble”.
If you want to check out an interactive simulation, check on this link.
Studies like this are invaluable in understanding our own planet. As a SF writer, they provide invaluable insights when it comes to build your own planets! Check out my own world-building in The Tau Ceti Diversion.
With the crew dead, and the starship’s fusion drive held back from a lethal explosion, Karic and the surviving officers reach a habitable planet – the last thing they expected was to find it already occupied . . .
Get it here!