Looming 'supermoon' triggersdebate

- On March 19, the moon will swing
around Earth more closely than it
has in the past 18 years, lighting
up the night sky from just 221,567
miles (356,577 kilometers) away.
On top of that, it will be full. And
one astrologer believes it could
inflict massive damage on the
planet.
Richard Nolle, a noted astrologer
who runs the website
astropro.com, has famously
termed the upcoming full moon at
lunar perigee (the closest
approach during its orbit) an
"extreme supermoon."
When the moon goes super-
extreme , Nolle says, chaos will
ensue: Huge storms, earthquakes,
volcanoes and other natural
disasters can be expected to
wreak havoc on Earth. (It should
be noted that astrology is not a
real science, but merely makes
connections between astronomical
and mystical events.)
But do we really need to start
stocking survival shelters in
preparation for the supermoon?
[ Photos: Our Changing Moon ] The
question is not actually so crazy.
In fact scientists have studied
related scenarios for decades.
Even under normal conditions, the
moon is close enough to Earth to
make its weighty presence felt: It
causes the ebb and flow of the
ocean tides .
The moon's gravity can even
cause small but measureable ebbs
and flows in the continents, called
"land tides" or "solid Earth tides,"
too. The tides are greatest during
full and new moons, when the sun
and moon are aligned either on
the same or opposite sides of the
Earth.
According to John Vidale, a
seismologist at the University of
Washington in Seattle and director
of the Pacific Northwest Seismic
Network, particularly dramatic
land and ocean tides do trigger
earthquakes. "Both the moon and
sun do stress the Earth a tiny bit,
and when we look hard we can
see a very small increase in
tectonic activity when they're
aligned," Vidale told Life's Little
Mysteries , a sister site to
SPACE.com.
At times of full and new moons,
"you see a less-than-1-percent
increase in earthquake activity,
and a slightly higher response in
volcanoes ."
The effect of tides on seismic
activity is greatest in subduction
zones such as the Pacific
Northwest, where one tectonic
plate is sliding under another.
William Wilcock, another
seismologist at the University of
Washington, explained: "When
you have a low tide, there's less
water, so the pressure on the
seafloor is smaller. That pressure is
clamping the fault together, so
when it's not there, it makes it
easier for the fault to slip."
According to Wilcock, earthquake
activity in subduction zones at low
tides is 10 percent higher than at
other times of the day, but he
hasn't observed any correlations
between earthquake activity and
especially low tides at new and full
moons. Vidale has observed only
a very small correlation.
What about during a lunar
perigee? Can we expect more
earthquakes and volcanic
eruptions on March 19, when the
full moon will be so close?
The moon's gravitational pull at
lunarperigee, the scientists say, is
not different enough from its pull
at other times to significantly
change the height of the tides and
thus the likelihood of natural
disasters. [ Infographic: Phases of
the Moon Explained ] "A lot of
studies have been done on this
kind of thing by USGS scientists
and others," John Bellini, a
geophysicist at the U.S. Geological
Survey, told Life's Little Mysteries.
"They haven't found anything
significant at all."
Vidale concurred. "Practically
speaking, you'll never see any
effect of lunar perigee," he said.
"It's somewhere between 'It has
no effect' and 'It's so small you
don't see any effect.'"
The bottom line is, the upcoming
supermoon won't cause a
preponderance of earthquakes,
although the idea isn't a crazy
one.
"Earthquakes don't respond as
much to the tides as you'd think
they would. There should actually
be more of an effect," said Vidale.
Most natural disasters have
nothing to do with the moon at all.
The Earth has a lot of pent up
energy, and it releases it anytime
the buildup gets too great. The
supermoon probably won't push it
past the tipping point, but we'll
know for sure, one way or the
other, by March 20.