Earth spins out
True Polar Wander. A term that, until recently, I was totally unfamiliar with. You can't look it up in the dictionary, it's not there. I've looked. However, a trawl of Google will reveal some almost incomprehensible sites that are passionate about this little known aspect of geological science.
Adam Maloof, Assistant Professor of Geosciences (Geology) at Princeton University in New Jersey knows a lot more about "true polar wander" than I do.
Adam has recently released research on evidence of TPW taken from the Svalbard, a remote Norwegian archipelago. The new paleomagnetic data suggests that the earth changed its magnetic orientation around 800 million years ago, so what could cause magnetic north to move?
On timescales longer than 10,000 years, magnetic north is thought to be the same as geographic north. In Svalbard Adam considered timescales of 1 to 10 million years, assuming that motion of the magnetic north pole also meant motion of the geographic pole. Evidence for coincident sea level, climate, and ocean chemistry changes support the idea that Svalbard was wandering with respect to the spin axis (magnetic and geographic north).
The theory of TPW speculates that if a large enough mass in the Earth’s interior formed, such as a large upwelling that might be expressed at the surface like a volcano, far enough away from the equator it would disturb the earth’s balance. The earth would tilt and rotate itself, eventually pulling the mass away from the earth’s axis towards the equator, to restore order.
Tiny grains of minerals, capable of holding a magnetic charge, point in the direction of magnetic north (which approximates true north on long time scales). When they eventually form solid rock it leaves an accurate record of the direction of the Earth’s magnetic field of the time. So if 800 million year old rock is magnetically pointing in a direction other than true north, we can assume north has moved.
A hot topic of debate in the science world is whether TPW can just be explained by something as well known as plate tectonics. Adam's new research is exciting because it corroborates data from several locations around the world, that after taking into account continental drift and plate tectonics still points to the Earth having "spun out" in the past.
So is it possible for humans and our environment altering activities to cause TPW, and wreak large scale havoc on our planet? Large amounts of TPW would be very difficult to cause today because earth's current shape is not particularly susceptible to small redistributions in mass.
However, Adam informs me currently we do experience "small amounts (less than one degree latitude) of TPW in response to the melting of ice sheets and the redistribution of water mass on the earth’s surface." Therefore, if we are responsible for global warming, then we could be responsible for small amounts of TPW.
So how does one drift into Geoscience?
At 18 years old Adam partook in a 6 week ski expedition across the Juneau Icefield, "I realized almost immediately I wanted to find a career that allowed me to walk in the mountains and live in a tent for at least a few months of the year. I also realised how little we actually understand of our natural world and how interesting and new Geoscience research could be."
Having recently returned to the States from a stint in Alice Springs and the Flinders Ranges collecting data to further support his research, at just 30 Adam has his ideal career and (literally) the world in the palm of his hands.
