Articles tagged with: Background

RHUM-RUM launched

Written by Guilhem Barruol, Karin Sigloch on Friday, 07 September 2012.

15 September 2012

Indian Ocean seen from Le Port de La Réunion

From Sept. to Nov. 2012, we will be installing most of our instruments: about 30 land stations in La Réunion, Mauritius, Madagascar, and the Seychelles, as well as 57 ocean-bottom seismometers during a month-long cruise aboard RV "Marion Dufresne". The cruise starts on September 22nd, we expect to be blogging regularly from the ship.

Le Volcan

Written by Chris Scheingraber on Thursday, 27 September 2012. Posted in La Réunion

26 September 2012

Many scientists who flew to La Réunion from continental Europe arrived some days in advance to have a look around this magnificent tropical island before embarking (embargoing?) on the Marion Dufresne. La Réunion's active volcanism is owed to its location on top of the mantle plume that our experiment plans to image by means of seismic tomography.

The "Piton de la Fournaise", the active volcano in the south-east of the island has erupted numerous times in the recent past, including an eruption lasting from August 2006 until January 2007.

Another big eruption, which occurred in 1986, increased the island size by as much as 25 hectares. The newly added area is called "Pointe de la table" and lies on the coast about 5 km north-east of Saint Philippe.

"Jardin volcanique - coastal shore line close to the famous 'Pointe de la table'

The whale and the butterfly (digression about rounds on the water)

Written by Jérôme Dyment on Monday, 08 October 2012. Posted in Cruise 2012

7 October 2012

On Rhum-Rum, we are not doing rounds in the water...  but nice drawings indeed!

Of us, marine geophysicists, who wander on the oceans, looking for indices to better understand how the seafloor forms, ages, and disappears, some are saying that we are doing rounds on the water. It is untrue, indeed! A short glimpse to the route map of cruise Rhum-Rum - routes achieved during the first leg, routes to be done during the second one - clearly shows that, if we do accumulate some mileage, it is certainly not doing circles but much more complicated figures, which await patiently an improbable Sigmund Freud to decipher their deep meaning, their psychoanalytic signification. This aspect appeared to me when, just after my PhD thesis - otherwise said in the Middle Age - I boarded the first Marion Dufresne for cruise MD67. Possibly affected by our short stop in Kerguelen Island when approaching the study area, our path was drawing a giant penguin superimposed to the structures of the Kerguelen Plateau and the Enderby Basin. Years later, when I was leading cruise Magofond 3 on R/V Suroît south-east of the Canary Islands, I rapidly noticed that our tracks were making a big M then a smaller A - we did not reach the end of the word, but were then making deep-towed magnetic profiles across the Cretaceous Quiet Zone to try to unravel one of the greatest remaining enigmas of geomagnetism. And today, finishing Rhum-Rum Leg 1, the two wide loops that we made to the East - almost touching Rodrigues, and Mauritius twice - and to the West - in a rather shy approach to the Big Island of Madagascar - let me think of the (truncated - we lost 6 days!) wings of a giant butterfly (Figure 1), whose body would be made of the inner circle of ocean bottom seismometers that we consciously dropped all over around La Reunion Island... Should we imagine the caterpillar, moving up from the deep Earth mantle with ascending currents of the inferred plume, cocooning in the heat of the Fournaise then metamorphosing to butterfly and taking advantage of our cruise to escape, like an allegory of the Truth coming out of the well - I wouldn't dare to say in what apparel!

As I write Leg 2 remains to be done, and I will unfortunately not be there to contribute more than through some maps - again - left onboard to the best use of the chief scientists. I already see, in the projected tracks, the shape of a whale (Figure 1), its noose on the Rodrigues Triple Junction - this peculiar point where three mid-ocean ridges meet. The whale's front follows the Central Indian Ridge, its mouth would be located in that small area of the Southwest Indian Ridge where eight ocean bottom seismometers will be deployed very near to each other - may be to detect a possible raging "baleenache"... Paradoxically, I imagine the dorsal fin on the side without any active ridge ("dorsale" in French), in the Madagascar and southern Mascarene basins, as an indication of other, fossil spreading centers that we would not have properly detected yet.

Now you know why I entitled this essay "the whale and the butterfly". It is open to analysts and other psychiatrists, professional or not, to further investigate the matter - delirium is not unusual in geosciences!