Saturday, March 19, 2011

A super full moon



From NASA

Today, a
full Moon of rare size and beauty will rise in the east at sunset.
It's a super "perigee moon"--the biggest in almost 20 years.

"The last full Moon so big and close to Earth occurred in March of 1993," says
Geoff Chester of the US Naval Observatory in Washington DC.
"I'd say it's worth a look."

Full Moons vary in size because of the oval shape of the Moon's orbit.


It is an ellipse with one side (perigee) about 50,000 km closer to Earth than the other (apogee).
Nearby perigee moons are about 14% bigger and 30% brighter than lesser moons that occur on the apogee side of the
Moon's orbit.

"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," adds Chester.

A perigee full Moon brings with it extra-high "
perigean tides," but this is nothing to worry about, according to NOAA.
In most places, lunar gravity at perigee pulls tide waters only a few centimeters (an inch or so) higher than usual.
Local geography can amplify the effect to about 15 centimeters (six inches)--not exactly a great flood.

The Moon looks extra-big when it is beaming through foreground objects--a.k.a. "
the Moon illusion."
Indeed, contrary to some reports circulating the Internet, perigee Moons do not trigger natural disasters.
The "
super moon" of March 1983, for instance, passed without incident.
And an almost-super Moon in Dec. 2008 also proved harmless.

Okay, the Moon is 14% bigger than usual, but can you really tell the difference? It's tricky.
There are no rulers floating in the sky to measure lunar diameters.
Hanging high overhead with no reference points to provide a sense of scale, one full Moon can seem much like any other.

The best time to look is when the Moon is near the horizon.
That is when illusion mixes with reality to produce a truly stunning view.
For reasons not fully understood by astronomers or psychologists, low-hanging Moons look unnaturally large when they beam through trees, buildings and other foreground objects.
Today, why not let the "Moon illusion" amplify a full Moon that's extra-big to begin with?
The swollen orb rising in the east at sunset may seem so nearby, you can almost reach out and touch it.
Don't bother. Even a super perigee Moon is still 356,577 km away.
That is, it turns out, a
distance of rare beauty.

Links :
  • DiscoverMag : Bad astronomy, No, the “supermoon” didn’t cause the Japanese earthquake
  • LiveSciences : 'Supermoon' lunacy: does the moon make us crazy?
  • Space : 'Supermoon' rises, biggest full moon in 18 years occurs Saturday night

Friday, March 18, 2011

Midway’s albatrosses survive the tsunami


National Geographic photographer Frans Lanting documents young Laysan
and Black-Footed Albatrosses on Hawaii's Midway Atoll as they learn to fly

From Wired

The famed albatrosses of
Midway Atoll took a beating from the tsunami, but their population will survive, say biologists on the islands.

There are, of course, more pressing concerns in the tsunami’s aftermath than wildlife, and some might balk at paying attention to birds right now.
But compassion isn’t a zero-sum game, and Midway Atoll is one of Earth’s natural treasures: 2.4 square miles of coral ringing a deep-sea mountaintop halfway between Honolulu and Tokyo, a flyspeck of dry land that’s home to several million seabirds.
(localization in the Marine GeoGarage)

Roughly two-thirds of all
Laysan albatrosses live on Midway’s two islands, as do one-third of all black-footed albatrosses, and about 60 people.
Many of them work at the
Midway Atoll National Wildlife Refuge.
They had time to prepare for the tsunami, which struck late on the night of March 10.
Nobody was hurt; after the waves receded, they checked on the wildlife.

An estimated 1,000 Laysan adults were killed, and tens of thousands of chicks, said Refuge official Barry Stieglitz.
Those figures represent just the first wave of mortality, as adults who were at sea when the tsunami hit may be unable to find their young on returning.
Chicks now wandering on shore may be doomed — but in the long run, the population as a whole will recover.

“The loss of all these chicks is horrible. It’s going to represent a significant portion of this year’s Laysan albatross hatch. But in terms of overall population health, the most important animals are the proven, breeding adults,” said Stieglitz.
“In the long term, the greatest impact would be if we lost more adults. The population should come through this just fine.”

On a sadder note, however, one of the wandering chicks is the
first short-tailed albatross to hatch on Midway in decades.
The species was hunted to near-extinction in the 19th century, its feathers so fashionable that a population of millions was reduced to a handful of juveniles who stayed at sea during the carnage. (Young short-tailed albatrosses live in the open ocean for several years before mating.)
About 3,000 of the species now survive, and a few have recently made a home on Midway.

“If the chick lost one parent, it could be in danger. If it lost both, it’s definitely out of luck,” Stieglitz said.


Wisdom was a lucky survivor

Another well-known avian denizen of Midway is Wisdom, a 60-year-old female Laysan albatross.
Banded for identification in 1956, Wisdom is the oldest known wild bird.
In February, she was spotted rearing a new chick.

“When I gaze at Wisdom, I feel as though I’ve entered a time machine,” wrote U.S. Fish and Wildlife Service biologist John Klavitter in an email.
“My mind races to the past and all the history she has observed through time.”

Midway’s Laysan albatrosses feed in waters off Alaska, flying about 50,000 miles each year as adults.
Wisdom has flown between 2 and 3 million miles in her lifetime, compensating for age with smarts and efficiency.
She hasn’t been spotted since the tsunami, but Stieglitz said the biologists haven’t looked for her yet.
Wisdom’s nest is on high ground. They’re not too worried about her.

Links :
  • BBCNews : Japan tsunami, thousands of seabirds killed near Hawaii
  • WHOI : WHOI oceanographer explores the mysteries of albatross flight

Thursday, March 17, 2011

USA NOAA update in the Marine GeoGarage


26
charts have been updated in the Marine GeoGarage (NOAA update january/february 2011)

  • 411 GULF OF MEXICO
  • 11330 MERMENTAU RIV TO FREEPORT LA-TX
  • 11451 MIAMI TO MARATHON AND FLORIDA BAY
  • 11472 PALM SHORES TO WEST PALM BEACH FLORIDA
  • 11474 BETHEL SHOAL TO JUPITER INLET
  • 12211 FENWICK ISLAND TO CHINCOTEAGUE INLET
  • 13215 BLOCK ISL SND-PT JUDITH TO MONTAUK PT CONN-RI
  • 13267 MASSACHUSETTS BAY MA
  • 13270 BOSTON HARBOR MA
  • 13392 GRAND MANAN CHANNEL SOUTHERN PART
  • 14850 LAKE SAINT CLAIR
  • 18424 BELLINGHAM BAY
  • 18652 SAN FRANCISCO BAY TO ANTIOCH
  • 11349 VERMILION BAY AND APPROACHES
  • 11490 APPROACHES TO ST JOHNS RIVER
  • 11508 ALTAMAHA SOUND GEORGIA
  • 13204 GEORGES BANK EAST PART
  • 13226 MT HOPE BAY RI-MA
  • 13233 MARTHAS VINEYARD MA
  • 16683 POINT ELRINGTON TO CAPE RESURRECTION
  • 17327 SITKA HARBOR AND APPROACHES
  • 18654 SAN PABLO BAY
  • 18659 SUISUN BAY MALLARD ISLAND TO ANTIOCH
  • 18773 SAN DIEGO BAY
  • 19481 MIDWAY ISLANDS
  • 25650 VIRGIN PASSAGE AND SONDA DE VIEQUES WEST INDIES
Today 1019 NOAA raster charts (2166 including sub-charts) are included in the Marine GeoGarage viewer.

Note : NOAA updates their nautical charts with corrections published in:
U.S. Coast Guard Local Notices to Mariners (
LNMs),
National Geospatial-Intelligence Agency Notices to Mariners (
NMs), and
Canadian Coast Guard Notices to Mariners (
CNMs)
While information provided by this Web site is intended to provide updated nautical charts, it must not be used as a substitute for the United States Coast Guard, National Geospatial-Intelligence Agency, or Canadian Coast Guard Notice to Mariner publications

Please visit the
NOAA's chart update service for more info.

Lost city of Atlantis, swamped by tsunami, may be found


Nature has a really sick sense of humour.
We watch in horror as Japanese towns sink into the sea —
even as word spreads that Atlantis has been found.

From Reuters

A U.S.-led research team may have finally located the lost city of
Atlantis, the legendary metropolis believed swamped by a tsunami thousands of years ago in mud flats in southern Spain.

"This is the power of tsunamis," head researcher
Richard Freund told Reuters.

"It is just so hard to understand that it can wipe out 60 miles inland, and that's pretty much what we're talking about," said Freund, a University of Hartford, Connecticut, professor who lead an international team searching for the true site of Atlantis.

To solve the age-old mystery, the team used a satellite photo of a suspected submerged city to find the site just north of Cadiz, Spain.
There, buried in the vast marshlands of the Dona Ana Park, they believe that they pinpointed the ancient, multi-ringed dominion known as Atlantis.

The team of archeologists and geologists in 2009 and 2010 used a combination of deep-ground radar, digital mapping, and underwater technology to survey the site.

Freund's discovery in central Spain of a strange series of "memorial cities," built in Atlantis' image by its refugees after the city's likely destruction by a tsunami, gave researchers added proof and confidence, he said.

Atlantis residents who did not perish in the tsunami fled inland and built new cities there, he added.

The team's findings will be unveiled on Sunday in "
Finding Atlantis," a new National Geographic Channel special.

While it is hard to know with certainty that the site in Spain in Atlantis, Freund said the "twist" of finding the memorial cities makes him confident Atlantis was buried in the mud flats on Spain's southern coast.

"We found something that no one else has ever seen before, which gives it a layer of credibility, especially for archeology, that makes a lot more sense," Freund said.

Greek philosopher
Plato wrote about Atlantis some 2,600 years ago, describing it as "an island situated in front of the straits which are by you called the Pillars of Hercules," as the Straits of Gibraltar were known in antiquity.
Using Plato's detailed account of Atlantis as a map, searches have focused on the Mediterranean and Atlantic as the best possible sites for the city.

Tsunamis in the region have been documented for centuries, Freund says.
One of the largest was a reported 10-story tidal wave that slammed
Lisbon in November, 1755.

Debate about whether Atlantis truly existed has lasted for thousands of years.
Plato's "dialogues" from around 360 B.C. are the only known historical sources of information about the iconic city.
Plato said the island he called Atlantis "in a single day and night... disappeared into the depths of the sea."

Experts plan further excavations are planned at the site where they believe Atlantis is located and at the mysterious "cities" in central Spain 150 miles away to more closely study geological formations and to date artifacts.

Links :
  • DiscoveryChannel : The Search for the Lost City of Atlantis I / II / III / IV / V
  • Time : Lost No Longer? Researchers Claim to Have Found 'Atlantis' in Spain

Wednesday, March 16, 2011

When will we learn?


Tsunami sources

From Newsweek by Dr. Coastas E. Synolakis, professor at the University of Southern California and director of the Hellenic Centre for Marine Research in Athens.

The malevolent earthquake and tsunami in Japan have jolted our minds back to the 2004 catastrophe in the Indian Ocean, as well as to last year’s tsunamis in Chile and Sumatra.
Gruesome comparisons are inevitable, as is the fatalism that follows such “acts of God.”
What can man do in the face of nature’s wrath?
Not everything, of course—and a natural disaster is always a most sobering reminder of our own limitations.
But it is clear—and painfully so—that the international community has not done a fraction of what it had hoped to do in the aftermath of the carnage in 2004, when the devastation in Banda Aceh, Phuket, Sri Lanka, and parts of Africa led to a global resolve to be better prepared for the next time.

The three tsunamis in the past 13 months—including Friday’s havoc in Japan—have devastated nearby coastlines.
In Chile in February 2010, people did evacuate, but mostly of their own accord.
A
tsunami warning was issued, and then mysteriously lifted, at the same time as the tsunami was climbing up the rugged Chilean coastline.
More than 200 died.
In Sumatra in October, nature and man worked against the victims; most people didn’t feel the earthquake strongly enough to trigger self-evacuation, and the tremor struck at night.
A crawl line appearing on all TV channels in Sumatra asking them to evacuate was not seen by people in the Mentawai Islands off Sumatra’s western coast because most villages there have no electricity.
Their first intimation of the incoming wave was its roaring sound just offshore.
More than 400 drowned.
Sirens did ring in Japan—this is, after all, one of the most civic-minded countries on earth—yet hundreds, if not thousands, died.
More than 50 nations had evacuated people as Newsweek went to press—some of them, no doubt, being overcautious.

What went wrong again?
As far as preparedness is concerned, the main reason is that we continue to be focused on past disasters, rather than on building tsunami-resilient communities around the globe.
We deploy sensors to warn us of where older tsunamis struck, but we are not doing enough to anticipate future events.
While more than 40 tsunamographs—the special instruments in the deep ocean developed by the United States’ National Oceanic and Atmospheric Administration—are now measuring tsunami heights around the Pacific adjacent to the U.S., people in French Polynesia and other Pacific Islands have to wait and wait, without knowing what is about to hit them.
And even in Japan, arguably the most tsunami-ready nation in the world, there are no tsunamographs to provide notification when it is safe for search-and-rescue operations to begin.
This is not an easy matter.
Tsunami floods can move at speeds exceeding 15mph.
People who don’t evacuate on time may be fighting for their lives while perched on trees or moving logs, and rescuers have little information on whether it is safe to move in immediately and rescue them or whether the next wave will be even bigger.
People who do evacuate may be drawn back to their homes by the lull between wave arrivals, only to be swept away by the next one.
As opposed to earthquakes that last, at worst, a few minutes, tsunamis can flood coastlines for several hours, particularly inside closed bays or harbors.
Even when people start evacuating immediately, they may not have time to reach high ground if the nearest hill is a few miles away.

What is alarming is how little has changed around the world in terms of an awareness of the simpler protective steps to take.
During the Samoan tsunami in September 2009, people who could easily have climbed to high ground in the hills behind them chose, instead, to evacuate by car.
Many drowned in their cars, which were struck in exodus traffic along narrow coastal roads. When the 2010 Chilean tsunami arrived in California, people in Santa Monica Beach were mesmerized by the rapid withdrawal of the shoreline and went out to gawk at stranded marine life.
It is a miracle that the tsunami was small and they were able to get away.

During the same event, and despite what ended up as a very accurate forecast by the NOAA, Hawaii undertook a costly massive evacuation.
By contrast, people in the Sumatran Mentawais—despite numerous tsunami drills since 2004—didn’t self-evacuate on time.
They had felt so many tremors that did not produce a tsunami that they had become a bit cynical, and this proved fatal on a wide scale.
In the Juan Fernández Islands off the coast of Chile, many more than 20 would have died had it not been for a high-school girl ringing a gong very early in the morning.
She was the only one to notice the incoming wave, a story quite reminiscent of the schoolgirl who saved hundreds of lives in Thailand in 2004 because she knew how to recognize the harbinger shoreline withdrawal that often accompanies tsunamis.

It is time that such nonsense stops.
The technology exists for accurate real-time forecasts.
In the U.S., the NOAA can now predict tsunami heights and currents in a few major West Coast cities, triggered by earthquakes anywhere in the Pacific, but the accuracy is limited by the number of tsunamographs offshore.
The lack of offshore sensors also limits the NOAA’s ability to predict the tsunami duration. Sirens are old-fashioned, but they help save lives in coastal emergencies.
Although they cost very little, few coastlines around the world have them, as many countries rely on broadcast media and cell-phone messages.
There is no substitute for loud, blaring sounds to get people to move.

Tsunamographs need to be deployed around the world, supplemented by inundation maps.
These are maps that show the extent of possible tsunami flooding from hypothetical earthquakes in their vicinity.
Even in the U.S., only California has completed its mapping efforts.
Alaska and Hawaii, the most vulnerable U.S. states, do not have modern tsunami flood maps for all their coastal communities.
While there are now regional warning centers in the Indian Ocean, there are none in the Mediterranean.
A huge plate boundary almost as long as the one off Sumatra lurks in the eastern part of the basin and has produced earthquakes and tsunamis of similar magnitude as Friday’s event off Japan a few times in the past 2,000 years.
Yet intercountry politics on setting jurisdictional boundaries, the illusions of national warning centers with futuristic control rooms, tens of millions of dollars in funding, and a very predictable denial of the hazard have resulted in a tsunami of inaction.
By serendipity, the same day the Japanese tsunami hit, European nations were gathered in UNESCO’s headquarters in Paris to discuss—for the seventh time since 2005—the logistics of creating a
warning system in the Mediterranean Sea.
The European Union could have a world-class warning system tomorrow if it could swallow its pride and pipe dreams and ask the NOAA’s
Pacific Tsunami Warning Center, which now covers the Pacific and Indian oceans and the Caribbean Sea, for coverage.
The PTWC is not perfect, but it is the best we’ve got.

However, a world-class warning system is only part of the tsunami story.
What the world needs are tsunami-resilient communities that plan ahead not for any particular tsunami but for a medley of coastal hazards, storm floods, sea-level rises, and hurricanes.
Evacuation drills and continuous education are keys to long-term survival.
Every time we fly, we are reminded to put on our seat belts and of how to use life vests.
We need to be reminded, every time we visit any coastline around the world, of the possibility of a tsunami and of the simple steps we ought to follow to save ourselves.
And to exemplify the principle, if you are close to the coast and see any unusual shoreline motions, or feel any tremor that lasts more than 30 seconds, evacuate inland or to high ground.

Links :

Tuesday, March 15, 2011

Japan quake effects length of day and GPS coordinates



This map (from NASA) shows the location of the March 11, 2011 earthquake in Japan,
as well as the foreshocks (dotted lines), including a 7.2-magnitude event on March 9,
and aftershocks (solid lines).
The size of each circle represents the magnitude of the associated quake or shock.


From Space

The massive earthquake that struck northeast Japan Friday (March 11) has shortened the length Earth's day by a fraction and shifted how the planet's mass is distributed.

A
new analysis of the 9.0-magnitude earthquake in Japan has found that the intense temblor has accelerated Earth's spin, shortening the length of the 24-hour day by 1.8 microseconds, according to geophysicist Richard Gross at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

Gross refined his estimates of the Japan quake's impact – which previously suggested a 1.6-microsecond shortening of the day – based on new data on how much the fault that triggered the earthquake slipped to redistribute the planet's mass.
A microsecond is a millionth of a second.

"By changing the distribution of the Earth's mass, the Japanese earthquake should have caused the Earth to rotate a bit faster, shortening the length of the day by about 1.8 microseconds," Gross told Space.com in an e-mail.
More refinements are possible as new information on the earthquake comes to light, he added.

The scenario is similar to that of a figure skater drawing her arms inward during a spin to turn faster on the ice.
The closer the mass shift during an earthquake is to the equator, the more it will speed up the spinning Earth.

One Earth day is about 24 hours, or 86,400 seconds, long.
Over the course of a year, its length varies by about one millisecond, or 1,000 microseconds, due to seasonal variations in the planet's mass distribution such as the seasonal shift of the jet stream.

The initial data suggests Friday's earthquake moved Japan's main island about 8 feet, according to
Kenneth Hudnut of the U.S. Geological Survey.
The earthquake also shifted Earth's figure axis by about 6 1/2 inches (17 centimeters), Gross added.

The Earth's figure axis is not the same as its north-south axis in space, which it spins around once every day at a speed of about 1,000 mph (1,604 kph).
The figure axis is the axis around which the Earth's mass is balanced and the north-south axis by about 33 feet (10 meters).

"This shift in the position of the figure axis will cause the Earth to wobble a bit differently as it rotates, but will not cause a shift of the Earth's axis in space – only external forces like the gravitational attraction of the sun, moon, and planets can do that," Gross said.

This isn't the first time a massive earthquake has changed the length of Earth's day.
Major temblors have shortened day length in the past.

The 8.8-magnitude earthquake in Chile last year also sped up the planet's rotation and shortened the day by 1.26 microseconds.
The 9.1 Sumatra earthquake in 2004 shortened the day by 6.8 microseconds.

And the impact from Japan's 8.9-magnitude temblor may not be completely over.
The weaker aftershocks may contribute tiny changes to day length as well.

The March 11 quake was the largest ever recorded in Japan and is the world's fifth largest earthquake to strike since 1900, according to the USGS.
It struck offshore about 231 miles (373 kilometers) northeast of Tokyo and 80 miles (130 km) east of the city of Sendai, and created a massive tsunami that has devastated Japan's northeastern coastal areas.

Nautical map of Japan Honshu East Coast DMA 97060 (NGA/NIMA)
& NASA Earth Observatory Flooded Coast near Sendai

At least 20 aftershocks registering a 6.0 magnitude or higher have followed the main temblor.

"In theory, anything that redistributes the Earth's mass will change the Earth's rotation," Gross said." So in principle the smaller aftershocks will also have an effect on the Earth's rotation. But since the aftershocks are smaller their effect will also be smaller."

Links :
  • BBCNews : How the quake has moved Japan / MSNBC : How the quake shifted Japan
  • CNN : Quake moved Japan coast 8 feet, shifted Earth's axis / NYTimes : Quake moves Japan closer to U.S. and alters Earth’s spin
  • NYTimes : Before and after high res satellite images of Japan (slider lets you compare before and after)
  • Geonet : nationwide GPS array of Japan / InsideGNSS : Japan researchers use GPS permanent array to measure devastating earthquake
  • NASA : GPS time series
  • GPSWorld : GPS shows dramatic position shifts from Japan earthquake

Monday, March 14, 2011

Why Japan's tsunami triggered enormous whirlpool

Whirlpool created by the earthquake off the coast of Japan, March 11, 2011

From LiveScience

The tsunami that hit northern Japan today created an enormous
whirlpool in a harbor off the east coast of that country.
According to researchers, whirlpools aren't unusual after waves of this size.

The tsunami was triggered by an 8.9-magnitude earthquake that struck off the coast of Japan at 2:46 p.m. Tokyo time.
Video footage shows a boat swirling in the massive eddy.
It's not known whether anyone was on the vessel.

Based on eye-witness accounts and video in recent years, whirlpools probably occur with some regularity after large tsunamis, said
Ruth Ludwin, a retired seismologist at the University of Washington in Seattle.

"Whirlpools have a big impact on the human imagination," Ludwin said.


ca. 1797-1858 - Whirlpool and Waves at Naruto, Awa Province - by Hiroshige
Image by © Christie's Images/CORBIS

"They're very notable and very frightening. But from the perspective of the geological record, they don't leave any particular sign that has been recognized so far."

Whirlpools happen because of the interaction between rushing water and the geology of the coastline and seafloor, Ludwin said.

"Obviously there is a lot of water that is being pushed around, and it is interacting with the shape, the bathymetry, near the coastline," she said.

"When a tsunami impacts the shoreline, some water overtops the shoreline and advances on the dry land in a manner somehow similar to a dam break wave,"
Hubert Chanson, a professor of hydraulic engineering and applied fluid mechanics at the University of Queensland in Australia, told LiveScience.
"This was seen during the
December 2004 tsunami in Indonesia and Thailand, as well as on Friday, 11 March 2011 in Japan.
At the same time, the impact of the tsunami waters on the coastline induces some very intense turbulent motion, and, with a suitable bathymetry, a large whirlpool may develop."

The first images and videos of post-tsunami whirlpools came out of the 2004 Indian Ocean tsunami, Ludwin said
(see abstract).
But eyewitness accounts from previous coastal quakes suggest that tsunami whirlpools are nothing new.
One was reported in the great
Lisbon earthquake of 1775, Ludwin said.
The Haida people of the
Queen Charlotte Islands off the coast of British Columbia have myths about a whirling wave of foam.

Apela Colorado, Ludwin's colleague with the
Worldwide Indigenous Science Network in Hawaii, has identified a petroglyph in southeastern Alaska that seems to show a whirlpool in the body of a sea monster.
In an abstract presented at the 2006 meeting of the Seismological Society of America, Colorado and Ludwin describe the native myths about that monster.
According to ancient tales, they wrote, the creature "inundates canoes, makes the salt-water boil, swallows fishermen, pushes fish into a cave, and creates a canoe passage by flopping across a spit."

Links :