Earth Observatory Blog

Submitted on 19 Sep 2016 by:

The MIRAGE research team returned from their month-long expedition, almost two months ago on 30 July 2016, with a great deal of data that was collected directly from the seafloor of the Wharton Basin in the Indian Ocean.

Although most of the data are still being analysed, there is one finding that Professor Satish Singh is happy to share with us now.

“On this expedition, we were successful in fully mapping a large seamount,” said Prof Singh, a visiting professor at the Earth Observatory of Singapore from the Institut de Physique du Globe de Paris. “It is always exciting to see an underwater...

Submitted on 30 Jul 2016 by:

It has been almost a month since we left the port of Colombo to make our way to the Wharton Basin, a place so remote that I can count on one hand the number of container ships and fishing boats I saw during our three weeks there.

In that time, we surveyed 90,000 square kilometres (km2) of seafloor, an area roughly the size of Ireland, acquiring bathymetry, gravity and magnetic data, sub-bottom profiles, and several dozen metres of sediments taken during two marathon coring operations.

The last time a research vessel was in the Wharton Basin, during the MEGA-TERA cruise of 2015, 7,500 km2of bathymetry was acquired, plus another 950 kilometres (km) of high-resolution seismic reflection data. By any measure, the MIRAGE has added enormously to the...

Submitted on 30 Jul 2016 by:

Last Saturday was barbecue night on the R/V Marion Dufresne, a chance for passengers and crew to mingle, cook their own dinner, and wear flip-flops on the ship’s main work deck, which is normally a safety-shoes-only zone. But rules relax on barbecue night, when everyone stands happily around a pair of open flames, sparks flying in the night as the ship pitches and rolls.

The crew begins preparing shortly after lunch, when everything that can be swept and hosed down is made shipshape. Flags are raised, representing both the ports of call the ship frequents and the nationalities of those on board. And then two horizontal halves of an oil drum are placed at the stern, filled with charcoal, and set ablaze.

Meanwhile, down in the kitchen, the cooks...

Submitted on 29 Jul 2016 by:

The first thing you need to know about the R/V Marion Dufresne’s engine room is that it is not a room at all. In fact, the engine — or engines, to be more precise — occupy an entire section of the ship, encompassing numerous decks from starboard to port. These decks are noisy and hot places, packed floor to ceiling, wall to wall, with ton upon ton of heavy machinery.

For Mr Sebastien Martin, Chief Engineer of the Marion Dufresne, this inhospitable setting is where he goes to work every day. It’s his office, you might say. A resident of Lyon, where he lives with a wife and their three teenage kids, Mr Martin has been the ship’s Chief Engineer since 2013, but his service aboard the vessel dates to 1999.

Working with a crew of a dozen or so engineers, electricians,...

Submitted on 27 Jul 2016 by:

Some people collect stamps, while others collect the cancellations on stamps, from “fancy cancels” to first-day issues. Within the world of cancellation collectors, there is a smaller, but no less enthusiastic, group of people who collect ship cancellations, which bear the seal of the vessel and are sometimes accompanied by the signature of its captain.

For such collectors, a Marion Dufresne cancellation can be quite a prize, rounding out a collection of research-vessel cancellations perhaps, or maybe a set of cancellations associated with France. Either way, the Marion Dufresne gets letters from all over the world, sent by people who only want to their letter returned with the ship’s unique stamp.

In fact, during a recent stamping session, as it’s called, six...

Submitted on 26 Jul 2016 by:

This week, the lab was buzzing with anticipation as we approached a seamount (an underwater mountain formed by volcanic activity), a small section of which had been mapped during last year’s MEGATERA cruise. The presence of the seamount was hardly a mystery, but details about its bathymetry were. We were about to get the first good look at this distinctive feature of the Wharton Basin. 

Since passing over the seamount four times in order to capture its contours as accurately as possible, MIRAGE scientists have learned that the seamount rises some 1,800 metres above the surrounding seafloor, is 30 or so kilometres across, and is cut from southeast to northwest by a deep fault. To the southeast of the...

Submitted on 25 Jul 2016 by:

When the prospect of joining the MIRAGE team was dangled before me this spring, I was briefed on the nature of the survey we’d be conducting, the importance to the region of understanding why enormous earthquakes were occurring in the middle of a seafloor plate, and the impressive resumes of the scientists who would be on board. But in every conversation, there was always this promise — it’s a French ship, so the food is going to be amazing. 

In fact, it has been. I’m not saying that absolutely every appetiser, main course, and dessert has been precisely to my taste (I’m not really a cream-sauce sort of guy), but we’ve been treated to a different menu at every meal, with nary a repeat. Three weeks on, we are still eating fresh fruit and vegetables, albeit in a more limited...

Submitted on 23 Jul 2016 by:

The less said about yesterday’s equator ceremony the better. Unfortunately, as the Communications Officer for the MIRAGE, I am duty bound to describe the events as they transpired.

To begin, the ceremony, as I understand it, is an exercise in shared ritual humiliation intended to create a bond between participants who have passed an invisible line on the globe, the equator, in something that floats. In this case, there were more than 20 of us who were initiated into this equator-crossing club. You can’t be a member of this club if you fly over the equator in a jet, and I suspect no one would care if you swam over it, either. But you can join the club — indeed, you must — if you cross the equator by ship or boat.

Several seamen described their experiences...

Submitted on 21 Jul 2016 by:

Obviously, no one on deck gets to see this momentous event since it’s happening 4.5 km below sea level, but the pipe’s collision with the seafloor can be followed on a monitor that tracks the tension of the polymer cable. As the coring unit makes its three-to-four hour descent, the tension on the cable is about 6.5 tons — it drops to zero when the pipe hits the seafloor, then spikes to about 11 tons as it’s pulled from the sticky mud. On the way back up, which takes another three-to-four hours, the tension is greater than it was on the way down, thanks to the weight of the mud now trapped inside the pipe.

What you can see on deck, though, is the process of assembling the coring machinery, as well as how the crew lowers the whole thing into the water and pulls it...

Submitted on 19 Jul 2016 by:

In my first post about coring, I explained why we selected our two coring sites, as well as what MIRAGE researchers hope to find once the samples we retrieved are analysed. But I left out the most fascinating part — how it’s done. 

The complete checklist of equipment used in coring is too numerous to detail here, but the major pieces of the CALYPSO Giant Piston Corer used on the Marion Dufresne are a coring pipe, a piston, and a trigger arm. Cranes and winches along the starboard side of the ship are designed to handle the pipe, while a custom-built winch below the main deck uncoils as much as 7,200 metres (m) of stiff polymer cable. It can lower the assembled coring unit — pipe, piston, and...

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