Friday, November 13, 2015

Magnetic anomalies of the world's largest volcano

 Tamu Massif, is a massive shield volcano that rises over 20 kilometers into the air
and covers an area the size of California or Japan.
Photo credit: Will Sager. 

From SchmidtOcean

Tamu Massif, located about 1000 miles east of Japan, is the largest known single volcano on Earth, but the process that created it remains a mystery.
With an area equivalent to Japan or California, the undersea volcanic mountain - a part of the western Pacific Shatsky Rise oceanic plateau - is believed to have formed during the late Jurassic period. Exactly how it formed in the age when dinosaurs still ruled is unknown, but scientists on this 32-day expedition aboard Falkor hope to reveal its origins.


Tamu Massif is located within the Shatsky rise.
Credit: Will Sager.

 Tamu Massif in the GeoGarage platform

Principal Investigator William Sager from the University of Houston Department of Earth and Atmospheric Sciences, and Geophysicist Masao Nakanishi from Chiba University, along with their science team, will transit over the western Pacific Ocean to Shatsky Rise, an undersea oceanic plateau where Tamu Massif is located.
As one of the few oceanic plateau volcanoes formed during a time of geomagnetic reversals, Tamu Massif holds a unique record of undersea geographic formation: magnetic anomalies in the oceanic crust.
This makes it easier to understand the underwater volcano’s history and the key interactions it has with the mid-ocean ridges.

Reversing poles

To appreciate geomagnetic reversals, one needs to know some aspects of Earth’s magnetic field.
Our planet has a magnetic field with North and South Poles, just like a bar magnet.
Geophysicists reason that the Earth’s magnetic field is created by the motion of the fluid iron outer core, which creates electric currents that in turn produce the magnetic field.
At certain times in the past, core flow changed, causing the poles to flip - what was once the North Pole is now the South, and vice versa.
Lava becomes magnetized as it solidifies to rock on the ocean floor, creating a record of the magnetic pole direction at the time.
The magnetic lava rock perturbs the Earth’s magnetic field, causing a negative or positive “magnetic anomaly” depending on whether it adds to or subtracts from the Earth’s field. 
In the ocean basins, the mid-ocean spreading ridges, divergent plate boundaries where oceanic crust is formed, record linear magnetic anomalies that parallel the spreading ridge crest.
Correlating the magnetic reversal pattern to time, scientists have used these magnetic anomalies to determine the age of the oceanic crust and the pattern of its development.
Because Tamu Massif formed during a time of geomagnetic reversals, its lavas also preserve magnetic anomalies that can be interpreted by scientists to show the construction of the volcano.

Using multibeam sonar systems and a marine magnetometer, the science team and Falkor crew plan on collecting seafloor and magnetic data in October and November of this year, to build a well-constrained magnetic anomaly map.
This map will allow for a better understanding of both Tamu Massif formation and its internal structure.
While it will not be possible to completely cover all of Tamu Massif with multibeam sonar bathymetry data, new underwater depth information collected on the cruise will substantially improve the knowledge of Tamu Massif topography and structure, all of which will help in understanding the monster volcano hidden beneath the sea.

 Cruise survey plan. Heavy lines show proposed cruise tracks.
Ingress and egress transit tracks are not shown.
Credit: Will Sager.

The Birth of a Giant

Shatsky Rise is one of the largest oceanic plateaus and is believed to have formed at the triple junction of three tectonic plates: the Pacific, the Farallon, and the Izanagi.
Like most oceanic plateaus, it is a huge volcanic mountain range consisting mainly of basalt rock covered with a generally thin veneer of sediments.
How such a massive volcano as Tamu Massif formed in this area is unknown.
Did it erupt as a huge boil on top of the mid-ocean ridges?
Did it disrupt and reorganize the seafloor, spreading the ground wide at the triple junction?
The answer to these fundamental questions will help scientists understand how oceanic plateaus form and how such volcanic eruptions interact with mid-ocean ridges and their underlying magma convection system.

 Model of hotspot volcanism.  A. Rising mantle plume. B. Outpourings of basalt generate the oceanic plateau. C. Less voluminous activity produces a volcanic chain. Image from Tasa Graphics.

Plume Head versus Fertile Mantle

There are two main, competing models that are debated about Tamu Massif’s formation.
The “plume head” hypothesis proposes that hot mantle under the ocean floor, begins to rise, forming a growing column of slowly flowing material.
When this “plume head” reaches the base of the outermost shell of the Earth, it bursts through, causing a massive eruption and intrusion of igneous material, as well as forming large oceanic plateaus (if undersea, as the case would be here).
This model gained acceptance mainly because geochronology data from several other geographic features appear consistent with short-lived and massive outpourings of lava.
This hypothesis excites Earth scientists because it implies periods of massive flux of mantle material to the surface.
Moreover, such massive eruptions also imply the release of large quantities of heat and gasses, which could have far-ranging environmental effects.
An alternative idea - the “fertile mantle” hypothesis - suggests eruptions occur because plate boundaries and cracks are releasing pressure above areas of upper mantle with lower melting temperatures.
This hypothesis implies that the source of plateau magma is shallow, and that the massive vertical mantle movement of the “plume head” hypothesis does not occur.
Simply, a “plume head” creates a large volcano in a huge, short, gushing eruption.
At a much slower pace, and a “fertile mantle” fosters extended surges of molten core, releasing stress at plate boundaries and forming a series of merging volcanoes over a longer period of time.
Oceanic plateau structure is key to figuring out whether this dichotomy is true, but plateau structure is poorly understood because these features are so large in size, as well as hidden and inaccessible beneath the sea.
Today, earth scientists still debate which of these two mechanisms provide a better explanation for large areas of volcanic rocks, known as igneous provinces.
Many oceanic plateaus contain significant complexities – unexpected ingredients or evidence - that do not lend themselves to clear origin certainty.
Depending on whom you talk to, the “plume head” model either needs amendments or should be dismissed.
As is often the case in science, neither hypothesis may be entirely correct, but these two concepts provide a framework for debate that will ultimately help geoscientists understand this important flux of material to the Earth’s surface.


Translating Evidence into Fact

The linear magnetic anomalies in the mid-ocean ridges are key to understanding how Tamu Massif formed.
One side (north) of Tamu Massif seems to have magnetic lineations, but the other (south) seems to have a broad, coherent anomaly caused by the whole volcano.
On this side, massive lava flows have been cored and imaged by acoustic profiling.
Magnetic lineations imply well-behaved, limited magmatic eruptions whereas the coherent anomaly implies a massive eruption.
Thus, it appears that Tamu Massif may have a Jekyll and Hyde personality.
To date, the magnetic data has been collected sparsely, and the science team hopes this cruise will fill the existing gaps with precise mapping of undersea geography and magnetic charting.
The goal is to combine the newly collected data with existing data to construct both magnetic and bathymetric contour maps of Tamu Massif.
Perhaps a revelation from tiny magnetically charged particles will explain the creation of one of Earth’s largest physical features.


 Links :

Thursday, November 12, 2015

We sailed the whole race by feel!

 Inside PRB : onboard with Vincent Riou and Sébastien Col

From Vendee Globe and Transat Jacques Vabre

At 1252 hrs today (Wednesday 11th November), Vincent Riou and Sébastien Col won the 2015 Transat Jacques Vabre, adding their name to the list of winners after an exceptional edition, which saw the first battle between the new IMOCA monohulls  and those from the previous generation.
They fully deserved this win after a transatlantic race they took control of from start to finish. It is a victory for a boat that is perfectly adapted to racing.
It also marks a fine victory for Vincent and Sébastien, who had never sailed together until a few months before tackling the Atlantic.

During the seventeen days of racing, the duo on PRB never gave up an inch after setting off from Le Havre.
Vincent and Sébastien found the perfect route with a series of tactical choices keeping the pressure up ion their rivals.
In particular, they found themselves in a battle against Banque Populaire VIII skippered by Armel Le Cléac’h and Erwan Tabarly and Groupe Queguiner sailed by Yann Eliès and Charlie Dalin, a battle that raged all the way across the Atlantic.

This second win in a row for Vincent in the Transat Jacques Vabre comes after a perfect season for the winner of the 2004 Vendée Globe.
With the boat he launched in 2010, he has asserted himself in every race against the newer IMOCAs, the foiling IMOCAs like Banque Populaire, but also against the 60-foot boats from the same generation.
Taking on board one of the top match racers, Sébastien Col, he didn’t make any mistakes.
Winner of the Artemis Challenge and the Rolex Fastnet Race, Vincent and Sébastien brought their complementary skills together to dominate this transatlantic race.
Vincent Riou: “It was a great contest, as in the end, our rivals never allowed us to ease off. Before yesterday morning, they were always within 35 miles of us.

Vincent and Sébastien had this goal in mind from the start in Le Havre.
They were of course, up there among the favourites, but the two sailors stressed their goal was to avoid any damage to their boat in the heavy seas in the first 36 hours of racing.
They were cautious but confident in the ability of their boat to ward off the attacks of the more recent boats in the class.
They knew where to place the cursor to ensure PRB made it through without letting Banque Populaire get away.
The latter in strong winds and on calm seas appeared at ease in this race.
Having to make do without their wind instruments from the first night of racing, Vincent and Sébastien had to sail for a long time using the age-old techniques, as they were unable to get any useful info at the nav desk.
Without info concerning the wind strength and direction, their race was no easy matter, but they never gave anything away and as they entered the Doldrums, put the pressure on Le Cleac’h / Tabarly.

After making it out of this area in the lead, Vincent and Sébastien found the perfect strategy to keep their opponents at a reasonable distance.
They spent the last few days of the race at the helm of PRB and showed utter determination, reading perfectly the weather conditions, which were more favourable for their monohull.

 Photo: B. Stichelbaut/PRB

Vincent Riou, skipper de PRB: “We’re pleased as this was no easy matter to finish in one piece. We can’t remember what we thought when we set off, but we do know that we wanted to remain cautious and that the first part of the race with all its dangers was going to be a key element. We knew we had to make it through and be at the front at the Azores. We managed to do that and after that we built upon that success. I think everything went to plan. With Seb, we worked well together. Honestly, it all worked out well for us."

It was a good battle behind us. They gave us no respite at all. Until yesterday morning I think there was never more than 35 miles of difference between first and second. On a race of 5400 miles that is permanent engagement. There was a bunch of lead changes, everyone seemed to get a crack at the top of the fleet. It was a good race and we got what we came for….competition! The choice to go west for the depression to the west of Ireland was the only option. For me it was safer for the boats because those who went left earlier were bounced around much more. On the long reach down the Atlantic then you just have to  keep the pace up. After eight days we found ourselves with a strange Doldrums. There it was game on a bit. But we got out well. You have to have strong nerves. It was complex. At the horn of Brazil it was interesting. I wanted to go offshore right away but (Jean Yves) Bernot our weather trainer had warned us about the coast of Brazil but it was still quite risky. But we got a little jump there. Everything went good. We got through the stormy front (at Cabo Frio) well, ahead of the others.

On the Transat Jacques Vabre:
“Today The Transat Jacques Vabre is for me a great classic of French sailing and should be considered as such. We came with intentions of winning the race. It was a hard race. If it lasted two or three more days, I think that the organizations would have suffered. "

What about the new generation of IMOCA?
"The new generation are very much in the learning phase, it is a time of discovery. We do not play in the same category. We led a boat which has foils. They are in discovery mode. Foils are the future of sailing. We will all have them one day. We cannot halt that progress. Today is a period of history, a hotbed of development. But what happened on this race needs to be analysed.”

Sebastien Col, co-skipper of PRB
"It was fun, it was impressive to see Vincent racing. It's a great chance I had to sail with him. He is  very complete. He is a master of many things like navigation. Physically it went well. Four years ago with François (Gabart), it was really hard, it's hard to get a new boat here safely.”

On his beautiful images of the race:
"The images….well there are rough seas with six metres waves on the first front. Then each part of the race has it specific things. We passed in between the Azores islands and between the islands of the archipelago of Fernando de Noronha. These are memorable things "


Vincent Riou
"We made a very special race. We worked this Transat Jacques Vabre by feel. From the first night race we had a navigation system failure. After that we did everything with one single display, COG and SOG. We never had wind strength or direction. We even thought of putting ribbons in the rigging as we did when we were sailed our 420 dinghies as nippers. We did everything without electronic help. But if you had told me before the start we would do this, I would have said not a chance. It’s not possible. But we had to sharpen up our senses and make it work. Then with some simple benchmarks, it's not too hard to find the right settings. But you always want to be well pressed for the best feelings. But for us the lesson is that you can learn from the feelings and it’s not so bad.” "

Sebastien Col
"Ultimately, this electronic damage is a good lesson. We realize that we are increasingly reliant on gizmos in life in general. As human beings we are capable of doing great things by instinct and feel. There is a nice lesson for a performance. And I learned how complete you need to be to sail an IMOCA. "


Links :




Wednesday, November 11, 2015

Sixty years of data show waves are getting stronger, threatening coastlines and infrastructure

An aerial view of Colun Beach in the Valdivian Coastal Reserve, Los Rios, Chile.
Photo © Nick Hall

From National Geographic by The Nature Conservancy’s Dr. Borja G. Reguero and Dr. Michael W. Beck


Climate change is modifying the way our oceans work in many different ways, including ocean acidification and water warming.
But where people really start to pay attention is where humans and oceans meet: the coast.

On the coast, most people have heard about sea level rise and assume that it is the major new problem affecting coastlines.
This is because we have a great deal of tangible scientific evidence that sea levels have been rising, and we are able to project future changes with relative certainty.


There have been some changes in coastal policies around sea level rise (SLR) but overall it is hard to garner action around SLR, because it is a creeping problem with some of its greatest impacts many decades away (i.e., many election cycles).

There’s another force out there that garners less attention yet has an even greater effect in shaping our coasts: waves.
It governs where we live and the coastal infrastructure we build.
In terms of both erosion and flooding, wave action is king.
Waves drive everything on our coastline.
They determine where the beaches, marshes and reefs occur.
They shape our headlands, our bays and our open coasts.
Waves determine where and in what direction we have built the hundreds of thousands of coastal defense structures (e.g., seawalls, breakwaters and dikes) we have erected over centuries.
Yet while sea level rise registers globally and while its future projections get clearer, we don’t yet have a similar degree of consensus and confidence when talking about the future of waves. Projections for future waves have until now been rare.
Historical changes observed by buoys, ships, and satellites point to increasing wave heights in many regions.

 Big seas at Porthcawl, United Kingdom.
Photo © Ben Salter/Flickr

It is the relentless pounding of these waves and the angle or direction of incoming wave energy that will determine our future coasts, so quickly expanding our understanding of current and future patterns in wave energy is critical for coastal management and decision making.
Recently, we have been able to show that wave energy has been changing throughout the last six decades.
 Differences in the mean wave power from the period 2001–2008 with respect to the decade of 1981–1990 (kW/m). After Reguero et al (2015).
In the southern ocean increased intensity of 20-30 kilowatts per meter in some regions of the ocean will intensifies the threat of erosion.
Even a modest increase in northern ocean threatens coastal communities.

After comparing the differences in wave energy throughout the decades, we found that there was more energy in waves in many regions from the 90s and 00s as compared to the 80s (see map). Indeed, the wave energy has been increasing greatly across nearly the entire Southern Ocean covering most of the coasts of South America, Africa, Australia and Micronesia.
The pattern is more complex in the northern hemisphere with Europe and the US West coast seeing less wave energy, but the US-East and Caribbean seeming somewhat more wave energy.

 Paul Grover captures the moment a huge wave crashes into the sea wall at Ilfracombe, North Devon.

Overall there are significant increases in wave energy and this affects many of the most at risk large cities and vulnerable small island states alike.
Moreover wave energy can increase greatly from more regular climatic events.
For example, with an upcoming El-Niño season, we can expect wave energy to increase in many areas across the Pacific Ocean.
Here in California, we are hoping the El Nino brings much needed rain (and the surfers hope for fun waves); we have forgotten for a moment the images of cliffside erosion and homes falling in to the water as they succumb to the erosion from these waves and wind.

Waves are powerful and their effects are easily observable on our coasts.
As wave energy increases, these effects will be more profound.
Most of our coastal structures were designed and permitted to withstand a very particular amount and direction of wave attack.
Flooding and erosion will accelerate.
Our coastal defense structures will fail more often and more spectacularly.

This will be bad news overall, but at least these climate change problems will be highly observable (even photogenic) and should motivate action from decision-makers.
We need to quickly and better understand these changes.
Our assessments of risk and where we build based on this risk must be updated.
Our future structures must be designed to withstand these changing forces.
By furthering the research in wave action and refining future wave projections, we can determine what’s in store for our coasts in an era that will also include rising seas and chart the best possible course to protect our coastal communities.


Tuesday, November 10, 2015

Lost at sea: the man who vanished for 14 months

Alvarenga’s journey from Mexico to the Marshall Islands.
Illustration: Guardian Graphics

From The Guardian by Jonathan Franklin 

In November 2012, José Salvador Alvarenga went fishing off the coast of Mexico.
Two days later, a storm hit and he made a desperate SOS.
It was the last anyone heard from him – for 438 days.
This is his story

As they motored across the lagoon in the Marshall Islands, deep in the middle of the Pacific Ocean, the policemen stared at the specimen laid out on the deck before them.
There was no hiding the fact that this man had been at sea for a considerable time.
His hair was matted upwards like a shrub.
His beard curled out in wild disarray.
His ankles were swollen, his wrists tiny; he could barely walk.
He refused to make eye contact and often hid his face.


Salvador Alvarenga, a 36-year-old fisherman from El Salvador, had left the coast of Mexico in a small boat with a young crewmate 14 months earlier.
Now he was being taken to Ebon Atoll, the southernmost tip of the Marshall Islands, and the closest town to where he had washed ashore.
He was 6,700 miles from the place he had set out from.
He had drifted for 438 days.

Floating across the Pacific Ocean, watching the moon’s light ebb and flow for over a year, Alvarenga had battled loneliness, depression and bouts of suicidal thinking.
But surviving in a vibrant world of wild animals, vivid hallucinations and extreme solitude did little to prepare him for the fact that he was about to become an international celebrity and an object of curiosity.

Days later, Alvarenga faced the world’s press.
Dressed in a baggy brown sweatshirt that disguised his reedy torso, he disembarked from a police boat slowly but unaided.
Expecting a gaunt and bedridden victim, a ripple of disbelief went through the crowd.
Alvarenga cracked a quick smile and waved to the cameras.
Several observers noted a similarity to the Tom Hanks character in the movie Cast Away.
The photo of the bearded fisherman shuffling ashore went viral.
Briefly, Alvarenga became a household name.


Who survives 14 months at sea?
Only a Hollywood screenwriter could write a tale in which such a journey ends happily.
I was sceptical, but as a Guardian reporter in the region, I began to investigate.
It turned out there were dozens of witnesses who had seen Alvarenga leave shore, who had heard his SOS.
When he washed ashore (in the same boat that he had left Mexico on), thousands of miles away, he was steadfast in his rejection of interviews – even posting a note on his hospital door begging the press to disappear.

Later, I would sit with Alvarenga for many hours, back at his home in El Salvador, as he described in detail the brutal realities of living at sea for more than a year.
Over the course of more than 40 interviews, he described his extraordinary survival at sea.
This is his story.

On 18 November 2012, a day after being ambushed at sea by a massive storm, Alvarenga was trying to ignore the growing pond of seawater sloshing at his feet.
An inexperienced navigator might have panicked, started baling and been distracted from his primary task: aligning the boat with the waves.
He was a veteran captain and knew that he needed to regain the initiative.
Together with his inexperienced crewmate, Ezequiel Córdoba, he was 50 miles out at sea, slowly negotiating a route back to shore.

The spray and crashing waves dumped hundreds of gallons of seawater into the boat, threatening to sink or flip them.
While Alvarenga steered, Córdoba was frantically tossing water back into the ocean, pausing only momentarily to allow his shoulder muscles to recover.

Alvarenga’s boat, at 25 feet, was as long as two pick-up trucks and as wide as one.
With no raised structure, no glass and no running lights, it was virtually invisible at sea.
On the deck, a fibreglass crate the size of a refrigerator was full of fresh fish: tuna, mahimahi and sharks, their catch after a two-day trip.
If they could bring it ashore, they would have enough money to survive for a week.

The boat, about 24-feet long, was empty aside from a small blue container in which Mr Alvarenga would hide, to seek shelter from the sun

The boat was loaded with equipment, including 70 gallons of gasoline, 16 gallons of water, 23kg (50lb) of sardines for bait, 700 hooks, miles of line, a harpoon, three knives, three buckets for baling, a mobile phone (in a plastic bag to keep it dry), a GPS tracking device (not waterproof), a two-way radio (battery half-charged), several wrenches for the motor and 91kg (200lb) of ice.

 The icebox in which Alvarenga hid from the sun.
Photograph: Matt Riding

Alvarenga had prepared the boat with Ray Perez, his usual mate and a loyal companion.
But at the last minute, Perez couldn’t join him.
Alvarenga, keen to get out to sea, arranged to go with Córdoba instead, a 22-year-old with the nickname Piñata who lived at the far end of the lagoon, where he was best known as a defensive star on the village soccer team.
Alvarenga and Córdoba had never spoken before, much less worked together.

Alvarenga tensely negotiated their slow advance toward the coast, manoeuvring among the waves like a surfer trying to glide and slice his way through.
As the weather worsened, Córdoba’s resolve disintegrated.
At times he refused to bale and instead held the rail with both hands, vomiting and crying.
He had signed up to make $50.
He was capable of working 12 hours straight without complaining and was athletic and strong.
But this crashing, soaking journey back to shore? He was sure their tiny craft would shatter and sharks would devour them.
He began to scream.

Alvarenga remained sitting, gripping the tiller tightly, determined to navigate a storm now so strong that harbourmasters along the coast had barred fishing boats from heading out to sea.
Finally he noticed a change in the visibility, the cloud cover was lifting: he could see miles across the water.
Around 9am, Alvarenga spotted the rise of a mountain on the horizon.
They were approximately two hours from land when the motor started coughing and spluttering.
He pulled out his radio and called his boss.
“Willy! Willy! Willy! The motor is ruined!”
“Calm down, man, give me your coordinates,” Willy responded, from the beachside docks in Costa Azul.
“We have no GPS, it’s not functioning.”
“Lay an anchor,” Willy ordered.
“We have no anchor,” Alvarenga said.
He had noticed it was missing before setting off, but didn’t think he needed it on a deep-sea mission.
“OK, we are coming to get you,” Willy responded.
“Come now, I am really getting fucked out here,” Alvarenga shouted.
These were his final words to shore.

As the waves thumped the boat, Alvarenga and Córdoba began working as a team.
With the morning sun, they could see the waves approaching, rising high above them and then splitting open.
Each man would brace and lean against a side of the open-hulled boat to counteract the roll.

But the waves were unpredictable, slapping each other in midair, joining forces to create swells that raised the men to a brief peak where they could get a third-storey view, then, with the sensation of a falling elevator, instantly drop them.
Their beach sandals provided no traction on the deck.

Alvarenga realised their catch – nearly 500kg (1,100lb) of fresh fish – was making the boat top heavy and unstable.
With no time to consult his boss, Alvarenga went with his gut: they would dump all the fish.
One by one they hauled them out of the cooler, swinging the carcasses into the ocean.
Falling overboard was now more dangerous than ever: the bloody fish were sure to attract sharks.

Next they tossed the ice and extra gasoline.
Alvarenga strung 50 buoys from the boat as a makeshift “sea anchor” that floated on the surface, providing drag and stability.
But at around 10am the radio died.
It was before noon on day one of a storm that Alvarenga knew was likely to last five days.
Losing the GPS had been an inconvenience.
The failed motor was a disaster.
Now, without radio contact, they were on their own.


The storm roiled the men all afternoon as they fought to bale water out of the boat.
The same muscles, the same repetitive motion, hour after hour, had allowed them to dump perhaps half the water.
They were both ready to faint with exhaustion, but Alvarenga was also furious.
He picked up a heavy club normally used to kill fish and began to bash the broken engine.
Then he grabbed the radio and GPS unit and angrily threw the machines into the water.

The sun sank and the storm churned as Córdoba and Alvarenga succumbed to the cold.
They turned the refrigerator-sized icebox upside down and huddled inside.
Soaking wet and barely able to clench their cold hands into fists, they hugged and wrapped their legs around each other.
But as the incoming water sank the boat ever lower, the men took turns leaving the icebox to bale for frantic 10- or 15-minute stints.
Progress was slow but the pond at their feet gradually grew smaller.

Darkness shrank their world, as a gale-force wind ripped offshore and drove the men farther out to sea.
Were they now back to where they had been fishing a day earlier?
Were they heading north towards Acapulco, or south towards Panama? With only the stars as guides, they had lost their usual means of calculating distance.

Without bait or fish hooks, Alvarenga invented a daring strategy to catch fish.
He kneeled alongside the edge of the boat, his eyes scanning for sharks, and shoved his arms into the water up to his shoulders.
With his chest tightly pressed to the side of the boat, he kept his hands steady, a few inches apart.
When a fish swam between his hands, he smashed them shut, digging his fingernails into the rough scales.
Many escaped but soon Alvarenga mastered the tactic and he began to grab the fish and toss them into the boat while trying to avoid their teeth.
With the fishing knife, Córdoba expertly cleaned and sliced the flesh into finger-sized strips that were left to dry in the sun.
They ate fish after fish.
Alvarenga stuffed raw meat and dried meat into his mouth, hardly noticing or caring about the difference.
When they got lucky, they were able to catch turtles and the occasional flying fish that landed inside their boat.

Within days, Alvarenga began to drink his urine and encouraged Córdoba to follow suit.
It was salty but not revolting as he drank, urinated, drank again, peed again, in a cycle that felt as if it was providing at least minimal hydration; in fact, it was exacerbating their dehydration.
Alvarenga had long ago learned the dangers of drinking seawater.
Despite their longing for liquid, they resisted swallowing even a cupful of the endless saltwater that surrounded them.

“I was so hungry that I was eating my own fingernails, swallowing all the little pieces,” Alvarenga later told me.
He began to grab jellyfish from the water, scooping them up in his hands and swallowing them whole.
“It burned the top part of my throat, but wasn’t so bad.”

After roughly 14 days at sea, Alvarenga was resting inside the icebox when he heard a sound: splat, splat, splat.
The rhythm of raindrops on the roof was unmistakable.
“Piñata! Piñata! Piñata,” Alvarenga screamed as he slipped out.
His crewmate awoke and joined him.
Rushing across the deck, the two men deployed a rainwater collection system that Alvarenga had been designing and imagining for a week.
Córdoba scrubbed a grey five-gallon bucket clean and positioned its mouth skyward.

Dark clouds stalked overhead, and after days of drinking urine and turtle blood, and nearly dying of thirst, a storm finally bore down on the men.
They opened their mouths to the falling rain, stripped off their clothes and showered in a glorious deluge of fresh water.
Within an hour, the bucket had an inch, then two inches of water.
The men laughed and drank every couple of minutes.
After their initial attack on the water supplies, however, they vowed to maintain strict rations.

After weeks at sea, Alvarenga and Córdoba became astute scavengers and learned to distinguish the varieties of plastic that bob across the ocean.
They grabbed and stored every empty water bottle they found.
When a stuffed green rubbish bag drifted within reach, the men snared it, hauled it aboard and ripped open the plastic.
Inside one bag, they found a wad of chewed gum and divided the almond-sized lump, each man feasting on the wealth of sensorial pleasures.
Underneath a layer of sodden kitchen oil, they found riches: half a head of cabbage, some carrots and a quart of milk – half-rancid, but still they drank it.
It was the first fresh food the two men had seen for a long time.
They treated the soggy carrots with reverence.

When they had several days’ worth of backup food, and especially after they had caught and eaten a turtle, Córdoba and Alvarenga briefly found solace in the magnificent seascape.
“We would talk about our mothers,” Alvarenga recalled.
“And how badly we had behaved.
We asked God to forgive us for being such bad sons.
We imagined if we could hug them, give them a kiss.
We promised to work harder so they would not have to work any more.
But it was too late.”

After two months at sea, Alvarenga had become accustomed to capturing and eating birds and turtles, while Córdoba had begun a physical and mental decline.
They were on the same boat but headed on different paths.
Córdoba had been sick after eating raw seabirds and made a drastic decision: he began to refuse all food.
He gripped a plastic water bottle in both hands but was losing the energy, and motivation, to put it up to his mouth.
Alvarenga offered tiny chunks of bird meat, occasionally a bite of turtle.
Córdoba clenched his mouth.
Depression was shutting his body down.

The two men made a pact.
If Córdoba survived, he would travel to El Salvador and visit Alvarenga’s mother and father.
If Alvarenga made it out alive, he’d go back to Chiapas, Mexico, and find Córdoba’s devout mother who had remarried an evangelical preacher.
“He asked me to tell his mother that he was sad he could not say goodbye and that she shouldn’t make any more tamales for him – they should let him go, that he had gone with God,” Alvarenga told me.
“I am dying, I am dying, I am almost gone,” Córdoba said one morning.
“Don’t think about that. Let’s take a nap,” Alvarenga replied as he lay alongside Córdoba.

“I am tired, I want water,” Córdoba moaned.
His breath was rough.
Alvarenga retrieved the water bottle and put it to Córdoba’s mouth, but he did not swallow.
Instead he stretched out.
His body shook in short convulsions.
He groaned and his body tensed up.
Alvarenga suddenly panicked.
He screamed into Córdoba’s face, “Don’t leave me alone! You have to fight for life! What am I going to do here alone?”
Córdoba didn’t reply.
Moments later he died with his eyes open.

“I propped him up to keep him out of the water. I was afraid a wave might wash him out of the boat,” Alvarenga told me.
“I cried for hours.”
The next morning he stared at Córdoba in the bow of the boat.
He asked the corpse, “How do you feel? How was your sleep?”
“I slept good, and you? Have you had breakfast?”
Alvarenga answered his own questions aloud, as if he were Córdoba speaking from the afterlife.
The easiest way to deal with losing his only companion was simply to pretend he hadn’t died.

Six days after Córdoba’s death, Alvarenga sat with the corpse on a moonless night, in full conversation, when, as if waking from a dream, he was suddenly shocked to find he was conversing with the dead.
“First I washed his feet.
His clothes were useful, so I stripped off a pair of shorts and a sweatshirt.
I put that on – it was red, with little skull-and-crossbones – and then I dumped him in.
And as I slid him into the water, I fainted.

***
When he awoke just minutes later, Alvarenga was terrified.
“What could I do alone? Without anyone to speak with?” he told me.
“Why had he died and not me? I had invited him to fish.
I blamed myself for his death.

But his will to live and fear of suicide (his mother had assured him that those who kill themselves will never go to heaven) kept him searching for solutions and scouring the ocean’s surface for ships.
Sunrise and sunset were best, as blurry shapes on the horizon were transformed into neat silhouettes and the sun was bearable.
With his eyesight fine-tuned, Alvarenga could now identify a tiny speck on the horizon as a ship.
As it approached, he would identify the type of vessel – usually a transpacific container ship – as it growled by.
These sea barges ploughed the sea effortlessly, and with no visible crew or activity on deck, they were like drones at sea.
Every sighting pumped Alvarenga with an energy boost that jolted him to wave, jump and flail for hours.
About 20 separate container boats paraded across the horizon, yet
Storms battered his small boat, but as he got farther out to sea, the storms seemed to become shorter, more manageable.

Alvarenga let his imagination run wild in order to keep sane.
He imagined an alternative reality so believable that he could later say with total honesty that alone at sea he tasted the greatest meals of his life and experienced the most delicious sex.
He was mastering the art of turning his solitude into a Fantasia-like world.
He started his mornings with a long walk.
“I would stroll back and forth on the boat and imagine that I was wandering the world.
By doing this I could make myself believe that I was actually doing something.
Not just sitting there, thinking about dying.”
With this lively entourage of family, friends and lovers, Alvarenga insulated himself from bleak reality.

When he was a small boy, his grandfather had taught him how to keep track of time using the cycles of the moon.
Now, alone in the open ocean, he was always clear as to how many months he had been adrift; he knew he had seen 15 lunar cycles while drifting through unknown territory.
He was convinced his next destination was heaven.

He was whizzing along on a smooth current, when suddenly the sky filled with shore birds.
Alvarenga stared.
The muscles in his neck tightened.
A tropical island emerged from the mist.
A green Pacific atoll, a small hill surrounded by a kaleidoscope of turquoise waters.

Hallucinations didn’t last this long.
Had his prayers finally been answered? Alvarenga’s racing mind imagined multiple disaster scenarios.
He could blow off course.
He could drift backward – it had happened before.
He stared at the land as he tried to pick out details from the shore.
It was a tiny island, no bigger than a football field, he calculated.
It looked wild, without roads, cars or homes.

With his knife, he cut away the ragged line of buoys.
It was a drastic move.
In the open ocean, with no sea anchor, he could readily flip during even a moderate tropical storm.
But Alvarenga could see the shoreline clearly and he gambled that speed was of greater importance than stability.

In an hour he had drifted near the island’s beach.
Ten yards from shore, Alvarenga dove into the water, then paddled “like a turtle” until a large wave picked him up and tossed him high on the beach, like driftwood.
As the wave pulled away, Alvarenga was left face down in the sand.
“I held a handful of sand like it was a treasure,” he later told me.

Making radio contact after landing on Ebon Atoll.
Photograph: Ola Fjeldstad

The famished fisherman crawled naked through a carpet of sodden palm fronds, sharp coconut shells and tasty flowers.
He was unable to stand for more than a few seconds.
“I was totally destroyed and as skinny as a board,” he said.
“The only thing left was my intestines and gut, plus skin and bones.
My arms had no meat. My thighs were skinny and ugly.”

Although he didn’t know it, Alvarenga had washed ashore on Tile Islet, a small island that is part of the Ebon Atoll, on the southern tip of the 1,156 islands that make up the Republic of the Marshall Islands, one of the most remote spots on Earth.
A boat leaving Ebon searching for land would either have to churn 4,000 miles north-east to hit Alaska or 2,500
miles south-west to Brisbane, Australia.
Had Alvarenga missed Ebon, he would have drifted north of Australia, possibly running aground in Papua New Guinea, but more likely continuing another 3,000 miles towards the eastern coast of the Philippines.

As he stumbled through the undergrowth, he suddenly found himself standing across a small canal from the beach house of Emi Libokmeto and her husband Russel Laikidrik.
“As I’m looking across, I see this white man there,” said Emi, who works husking and drying coconuts on the island.
“He is yelling. He looks weak and hungry.
My first thought was, this person swam here, he must have fallen off a ship.”

After tentatively approaching each other, Emi and Russel welcomed him into their home.
Alvarenga drew a boat, a man and the shore.
Then he gave up.
How could he explain a 7,000-mile drift at sea with stick figures? His impatience simmered.
He asked for medicine.
He asked for a doctor.
The native couple smiled and kindly shook their heads.
“Even though we did not understand each other, I began to talk and talk,” Alvarenga told me.
“The more I talked, the more we all roared with laughter. I am not sure why they were laughing. I was laughing at being saved.”

After a morning of caring for and feeding the castaway, Russel sailed across a lagoon to the main town and port on the island of Ebon to ask the mayor for help.
Within hours a group, including police and a nurse, had come to rescue Alvarenga.
They had to persuade him to get on a boat with them back to Ebon.
While they nursed this wild-looking man back to health and tried to coax out details of his journey, a visiting anthropologist from Norway alerted the Marshall Islands Journal.

Written by Giff Johnson, the first story went out under the Agence France-Presse (AFP) banner on 31 January and outlined the remarkable contours of Alvarenga’s story.
Reporters in Hawaii, Los Angeles and Australia scrambled to reach the island to interview this alleged castaway.
The single phone line on Ebon became a battleground, as reporters tried to discover tantalising details.
Alvarenga’s story had enough hard facts to make it plausible: the initial missing person report, the search-and-rescue operation, the correlation of his drift with known ocean currents, and the fact that he was extremely weak.

But a debate erupted online and in newsrooms around the world: was this the most remarkable survivor since Ernest Shackleton, or the biggest fraud since the Hitler diaries?
Officials tracked down Alvarenga’s supervisor, who confirmed that the registration number of the boat he had washed up in was the same as the one that had left port on 17 November 2012, and vanished.
Guardian reporter Jo Tuckman interviewed Mexican search-and-rescue official Jaime Marroquín, who detailed the desperate hunt for Alvarenga and Córdoba that followed.
“The winds were high,” Marroquín said.
“We had to stop the search flights after two days because of poor visibility.”

I began to investigate, talking to people up and down the coast of Mexico.
I looked at medical records, studied maps, and spoke to survival experts, ranging from the US Coast Guard to the Navy Seals, as well as Ivan MacFadyen and Jason Lewis, two adventurers who have crossed that stretch of the Pacific.
I spoke with oceanographers and commercial fishermen familiar with the area.
Everyone confirmed that Alvarenga’s version of life at sea was in line with what they would expect.
When he arrived at hospital in the Marshall Islands, he was debriefed by US embassy officials who described multiple scars on Alvarenga’s very damaged body.
“He was out there for a long time,” the US ambassador said.

 Back home in El Salvador.
For months he was in shock, afraid of the water.
Photograph: Oscar Machon

Meanwhile back in the Marshall Islands, Alvarenga’s medical condition steadily worsened.
His feet and legs were swollen.
The doctors suspected the tissues had been deprived of water for so long that they now soaked up everything.
But after 11 days, doctors determined that Alvarenga’s health had stabilised enough for him to travel home to El Salvador, where he would be reunited with his family.

He was diagnosed with anaemia and doctors suspected his diet of raw turtles and raw birds had infected his liver with parasites.
Alvarenga believed the parasites might rise up to his head and attack his brain.
Deep sleep was impossible and he thought often of Córdoba’s death.
It was not the same to be celebrating survival alone.
As soon as he was strong enough, he travelled to Mexico to fulfil his promise and deliver a message to Córdoba’s mother, Ana Rosa.
He sat with her for two hours, answering all her questions.

Life on land has not been straightforward: for months, Alvarenga was still in shock.
He had developed a deep fear of not only the ocean, but even the sight of water.
He slept with the lights on and needed constant company.
Soon after coming ashore, he appointed a lawyer to handle the media requests that came in from all over the world.
He later changed representation, and his former lawyer filed a lawsuit demanding a million-dollar payout for an alleged breach of contract.

It wasn’t until a year later, when the fog of confusion subsided and he scanned the maps of his drift across the Pacific Ocean, that Alvarenga began to fathom his extraordinary journey.
For 438 days, he lived on the edge of sanity.
“I suffered hunger, thirst and an extreme loneliness, and didn’t take my life,” Alvarenga says.
“You only get one chance to live – so appreciate it.”

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Monday, November 9, 2015

Scientists map source of Northwest’s next big quake

Overview map of the Cascadia Subduction Zone and the Cascadia Initiative seismic deployment.
The ocean floor Cascadia Initiative stations are shown in orange and red; the onshore USArray station are purple.
Moderate earthquakes around the Juan de Fuca oceanic plate are shown grey; the purple swath illustrates the Cascadia megathrust fault that has and will generate magnitude 9 earthquakes.
The Cascadia Initiative will study plate tectonic processes across the entire Jan de Fuca plate including the creation and destruction of the plate, and earthquake processes along the megathrust.

From Berkeley by Robert Sanders

A large team of scientists has nearly completed the first map of the mantle under the tectonic plate that is colliding with the Pacific Northwest and putting Seattle, Portland and Vancouver at risk of the largest earthquakes and tsunamis in the world.
A new report from five members of the mapping team describes how the movement of the ocean-bottom Juan de Fuca plate is connected to the flow of the mantle 150 kilometers (100 miles) underground, which could help seismologists understand the forces generating quakes as large as the destructive Tohoku quake that struck Japan in 2011.

“This is the first time we’ve been able to map out the flow of mantle across an entire plate, so as to understand plate tectonics on a grand scale,” said Richard Allen, a professor and chair of earth and planetary science at the University of California, Berkeley, and the senior author of a paper published online Nov. 2 in the journal Nature Geoscience.
“Our goal is to understand large-scale plate tectonic processes and start to link them all the way down to the smallest scale, to specific earthquakes in the Pacific Northwest.”

The major surprise, Allen said, is that the mantle beneath a small piece of the Juan de Fuca plate is moving differently from the rest of the plate, resulting in segmentation of the subduction zone. Similar segmentation is seen in Pacific Northwest megaquakes, which don’t always break along the entire 1,000-kilometer (600-mile) length, producing magnitude 9 or greater events.
Instead, it often breaks along shorter segments, generating quakes of magnitude 7 or 8.

 An ocean bottom seismometer being retrieved after spending 10 months on the floor of the Pacific Ocean to map the mantle 100 miles underneath the Juan de Fuca plate.

Plate tectonics

The Juan de Fuca plate offshore of Oregon, Washington and British Columbia is small – about the size of California and 50-70 kilometers thick – but “big enough to generate magnitude 9 earthquakes” as it’s shoved under the continental North American plate, Allen said.
Because of the hazard from this so-called Cascadia Subduction Zone, a recent New Yorker article portrayed the area as a disaster waiting to happen, predicting that “an earthquake will destroy a sizable portion of the coastal Northwest.”

But little is known about the tectonic plates submerged under the oceans, how they are linked to processes inside the earth, such as the melted mantle rock underlying them, or how the crust and mantle interact to cause megathrust earthquakes at subduction zones.

The Juan de Fuca plate is one of seven major and dozens of minor plates that cover the earth like a jigsaw puzzle, pushed around by molten rock rising at mid-ocean ridges and, at their margins, diving under other plates or ramming into them to generate mountain ranges like the Himalayas.
The largest of Earth’s tectonic plates, the Pacific plate, is moving eastward and plunging under the entire western edge of the Americas, creating a “ring of fire” dotted with volcanoes and mountain ranges and imperiled by earthquakes.

Until now, however, scientists have deployed only a handful of seismometers on the seabed worldwide to explore the mantle underlying these plates, said Allen, who also is director of the Berkeley Seismological Laboratory and one of the co-principal investigators for the $20 million Cascadia Initiative.
Led by the University of Oregon, the initiative is funded by the National Science Foundation to develop new underwater and on-shore seismic instruments to measure the plate’s interaction with the mantle or asthenosphere, and monitor quake and volcanic activity at the trench off the coast where the Juan de Fuca plate subducts under the North American plate.

“The experiment was unprecedented in that there were 70 seismometers deployed at a time, sitting there for 10 months, which is much bigger than any other ocean-bottom experiment ever done before,” said Robert Martin-Short, a UC Berkeley graduate student and first author of the paper.
“We’ve learned a lot from the deployment of these new instruments, and now have a giant array that we know works well on the sea floor and which we can move somewhere else in the future for a similar experiment.”

While the deployment of seismometers at 120 sites on the ocean floor was a technical challenge, Allen said, “the offshore environment is much simpler, the plates are thinner and more uniform than continental plates and we can see through them to get a better sense of what is going on beneath.”

Since 2012, the team has made 24 two-week ocean voyages to place and retrieve the sea bed seismometers, providing dozens of students – undergraduates and graduate students from UC Berkeley, Columbia University, the universities of Oregon and Washington and Imperial College in the UK – an opportunity to participate in field research.
The last of the sea bed seismometers were pulled up this month and the data is being prepared for analysis.

Based on the first three years of data, Allen and his team confirmed what geophysicists suspected.
At the mid-ocean Juan de Fuca ridge about 500 kilometers (300 miles) offshore of Seattle – the western edge of the Juan de Fuca plate – the flow of the mantle below the plate is perpendicular to the ridge, presumably because the newly formed plate drags the underlying mantle eastward with it.

As the plate moves away from the ridge, the mantle flow rotates slightly northward toward the trench. At its eastern margin, the plate and underlying mantle move in alignment, perpendicular to the subduction zone, as expected.
Presumably, the subducted portion of the plate deep under the trench is pulling the massive plate downward at the same time that the emerging lava at the mid-ocean spreading ridge is elevating the plate and pushing it eastward.

Cascadia Basin with the GeoGarage

 The red line outlines the Juan de Fuca plate that is moving eastward, shoved under the continental North American plate and generating megathrust earthquakes.

Gorda plate adrift

Allen and his colleagues found, however, that a part of the Juan de Fuca plate called the Gorda plate, located off the Northern California coast, is not coupled to the mantle, leaving the mantle beneath Gorda to move independently of the plate above.
Instead, the Gorda mantle seems to be aligned with the mantle moving under the Pacific plate.
“The Juan de Fuca plate is clearly influencing the flow of the mantle beneath it, but the Gorda plate is apparently too small to affect the underlying mantle,” he said.

This change in mantle flow produces a break or discontinuity in the forces on the plate, possibly explaining segmentation along the subduction zone.
“When you look at earthquakes in Cascadia, they sometimes break just along the southern segment, sometimes on the southern two-thirds, and sometimes along the entire length of the plate,” Allen said. “The change in the mantle flow could be linked to that segmentation.”

The Cascadia Initiative is a community experiment designed by the research community with all data immediately available to the public.
NSF funded the project with money it received through the 2009 stimulus or American Recovery and Reinvestment Act.
Eleven scientists, including Allen, from across the U.S. formed the Cascadia Initiative Expedition Team responsible for the offshore seismic deployment.

Allen and Martin-Short’s co-authors on the Nature Geosciences paper are Ian Bastow and Eoghan Totten of Imperial College and UC Berkeley geophysicist Mark Richards, a professor of earth and planetary science.
Richards helped develop the geodynamic model of the interaction between the plate and the mantle that explains how the faster-moving Pacific plate could override the influence that the Gorda plate has on the mantle below.