The tsunami and the moon

At the time of writing this, 1 March, there are many storms around the world and more than one earthquake event. Yesterday, 28th, was the day the moon was the third closest to Earth for the whole year, called perigee. Perigee and its opposite number apogee, when the moon is furthest away, cause extreme events. During perigee levitational force upwards is maximised, and gravitational force downwards minimised. With apogee gravitational force is maximised. Tectonic plates can be prised open as a result of both.

Full moon is today. We also have, right now as a result of full moon+close perigee, the highest tides since March 2002, and they won't be as high again until February 2014. There are corresponding tides in the land and in the air. The moon cannot tell the difference between air, water and land. It pulls everything it can. Tectonic plates will move at the same time as the highest tides of the month, which is why most earthquakes occur under the sea. Full moons maximise earthquake times. Simply google full moons and earthquakes to read some of it. The full moon/perigee/apogee combination does not cause every earthquake event, but many of the bigger ones seem to coincide. Cyclonic systems are especially potent around full moon. That is why after today the threat will be over.

Other events around full moon/perigee/apogee have been the Samoan tsunami of 2009, the Chinese earthquake in Yunnan last year that took out 10,000 houses, followed a lunar pulse later by our Te Anau event. Further back there was the Asian tsunami of 2004, the Napier earthquake of 1931.

Why would full moon cause these events? At full moon time the moon is opposite the sun on the other side of earth, exerting a gravitational pull on earth and on everything on the earth. Go back two weeks in your imagination. At New moon the moon and sun are in line with Earth and are exerting their double gravitational pull. One way to imagine it is as a two team tug of war in which one team is pulling a rope tied to a large ball (the sun+moon pulling at the Earth) and the other team is pulling the other way (the gravity of Earth that resists the sun+moon's pull). When the new moon pull occurs, forces tend more towards the moon. This includes tides and air movements. Two weeks later the sun/moon pull is around full moon and takes on a different intensity, as the team on the other side pulling the rope find the forces flowing in their direction.

Another factor in the mix is the moon's 'node', sometimes called a 'nodal crossing', which is when the moon sits at what we call the ecliptic which is the plane all the planets are on as they circle Earth. At non-nodal times the moon sidesteps the ecliptic up to 5 deg to either side. This is called 'inclination'. Think of it this way, that the team pulling the rope sidestep slightly to the left or right. Their pulling force will always more potent when it is in the direct line (the node). When the moon is nodal at the same time as full moon you get an eclipse, which is why in the past when the moon was closer to earth (it is moving away at the rate of an inch per year) eclipses were times of severe weather events and were much feared.

The moon was nodal on the 25th, so no eclipse this time. The node has the effect of focussing the moon’s energies, for instance, fishing not too far from nodes is generally pretty good. Nodes add to tides and to weather. If moisture is around, then fronts will typically follow nodal crossings. But because the node of the 25th has just gone (next nodal crossing is on 10 March), it means wet cold weather which we got a few days ago has lessened over the past few days. In fact the next two weeks should be relatively dry for the North Island. This node has clearly contributed to the "setting up" of the current severe events.

The next combination of full moon+perigee is in a month's time around 28-30 March. The preceding node will be on the 25th. It again will have the potential to create another round of storms, large tides and earthquakes.