Weekend Feature: Today's Rare "Supermoon" is the Closest in 18 Years-Could It Trigger More Earthquakes and Tsunamis? NASA Says "No"

 
Despite one astrologer’s fears that today's rare “Supermoon” will cause a natural disaster, NASA experts say there is nothing supernatural about it. This afternoon, the moon will be the closest it's been to Earth in more than 18 years. The "Supermoon," as astronomers have dubbed it, will appear at 3 p.m. ET at a distance of 221,565 miles away.

Tonight's phenomena is caused by the moon's oval orbit. At one end of the orbit –-- the perigee –-- the moon is about 31,000 miles closer to Earth than at its farthest point, the apogee.

It’s rare for a full moon to coincide with a perigee. The most recent example was the near supermoon in 2008, when the full moon occurred four hours before perigee. Tonight's occurrence is even closer to the full moon and perigee lining up.

"The full Moon of March 19th occurs less than one hour away from perigee – a near-perfect coincidence that happens only 18 years or so," Geoff Chester of the US Naval Observatory said in a NASA report. From one orbit to the next, perigees and apogees vary. Tonight’s perigee will bring the moon about as close as it ever gets.

According to NASA, perigee moons are about 14 percent larger, and 30 percent brighter than apogee moons, though it’s hard to tell the difference with the naked eye. For the best view of the supermoon, NASA has suggested viewing it when it’s lower in the sky.

Japan's massive 8.9-magnitude earthquake and deadly tsunami in Japan triggered world-wide viral headlines about the destructive environmental power of the upcoming "supermoon."

The term "supermoon" originated on the website of astrologer Richard Nolle who reported that a new or full moon at 90% or more of its closest perigee (the point in the orbit nearest to the center of the earth) qualifies as a "supermoon," making the March 19 full moon a supermoon, because the crest of the moon’s full phase comes within an hour of the moon’s closest point to Earth.

According to Dr. James Garvin, chief scientist at NASA's Goddard Space Flight Center, a 'supermoon' is a situation when the moon is slightly closer to Earth in its orbit than on average, and this effect is most noticeable when it occurs at the same time as a full moon. So, the moon may seem bigger although the difference in its distance from Earth is only a few percent at such times.

It is called a "supermoon" because this is a very noticeable alignment that at first glance would seem to have an effect. The 'super' in supermoon is really just the appearance of being closer, but unless we were measuring the Earth-Moon distance by laser rangefinders (as we do to track the LRO [Lunar Reconnaissance Orbiter] spacecraft in low lunar orbit and to watch the Earth-Moon distance over years), there is really no difference. The supermoon really attests to the wonderful new wealth of data NASA's LRO mission has returned for the Moon, making several key science questions about our nearest neighbor all the more important.

The effects on Earth from a supermoon are minor, and according to the most detailed studies by terrestrial seismologists and volcanologists, the combination of the moon being at its closest to Earth in its orbit, and being in its 'full moon' configuration (relative to the Earth and sun), should not affect the internal energy balance of the Earth since there are lunar tides every day.

The Earth has stored a tremendous amount of internal energy within its thin outer shell or crust, and the small differences in the tidal forces exerted by the moon (and sun) are not enough to fundamentally overcome the much larger forces within the planet due to convection (and other aspects of the internal energy balance that drives plate tectonics). Nonetheless, these supermoon times remind us of the effect of our 'Africa-sized' lunar neighbor on our lives, affecting ocean tides (and a visible aspect of how our planet is part of the solar system and space).

There are references, however, in scientific literature of a possible connection between full moons and seismic activity. The moon causes tides in the solid core of the Earth, just as it causes ocean tides. Most experts rule out the assumption that a close full moon might cause geologic activity to increase.

But, it is pure speculation that a "supermoon" phase could cause tectonic plate shifts. We'll  test the theory during tonight's supermoon---which coincides with the moon’s closest point to Earth---and see if it bring more earthquakes and tsunamis.

The Daily Galaxy via NASA, monitor.com, earthsky.org, and fastcompany.com

Comments

[Bob Greenwade]

Actually, I'd say that the answer is "Yes" -- what physicists call a "nonzero probability."

However, an earthquake triggered by a supermoon would have to be one that was already getting to happen any day now -- in other words, it was on a proverbial hair trigger. Also, the supermoon wouldn't make it any more severe, at least not perceptibly; it would mainly alter the timing, and even that by no more than a few days.

In that sense, the approaching supermoon might (and I emphasize that word, *might*) have already triggered last week's quake in Japan -- although, as I implied, that would have happened by now anyway, and with roughly the same result.

Personally, I'd be a little more nervous about a lunar perigee happening during a new moon near the summer solstice.

[Neil Bates]

No, I don't think this situation has noticeable practical effect. The "supermoon" is being a little closer than usual and, the Moon's orbit is elliptical anyway. This event just makes the Moon marginally closer than the average periselene.