J.-A. Olive

What a day!
We visited Kerguelen station, met king penguins and elephant seals, and walked on the "Desolation Island".

Just a few days before reaching the OHA-GEODAMS area, this was an unforgettable stop in the middle of the Southern Ocean.

Cheers to the penguins 🐧

On our way to the Southeast Indian Ridge and it’s all hands on deck 🚢🔧
From building tripods for acoustic beacons to installing the transducer and modem in the ship’s forward hold, operational prep is well underway!

group photo in front of Crozet

Penguin crowd at la Manchotière from Possession Island

A standard croziflette

The 2026 GEODAMS team safely arrived close to Possession Island in the Crozet archipelago a few days ago. A penguin crowd welcomed us under a very bright sky and with the traditional croziflette that follows... 🐧 🍽️

We’ve had our fill, both for the eyes and the stomach.

The OHA-GEODAMS team is back to document how the Indian Ocean grows.

Cruise #3 on board Marion Dufresne left La Réunion Island a few days ago to maintain the multi-sensor observatory on the South East Indian Ridge. Follow us on this new adventure!

(credit photo: Ewen & Didier)

Alvin submersible working at an active high-temperature hydrothermal vent located on the East Pacific Rise at 2,510 m depth. CREDIT: Dan Fornari, Woods Hole Oceanographic Institution and Thibaut Barreyre, CNRS - U. Brest; National Deep Submergence Facility, HOV Alvin Team, WHOI-MISO Facility, National Science Foundation.

Researchers successfully predicted a seafloor eruption at a midocean ridge in April 2025 by tracking hydrothermal fluid temperatures. A 35-year record reveals that temperature increases from 350°C to 390°C may reliably forecast eruptions. In PNAS: https://ow.ly/lrwZ50Xf1v0

🎓 #PhD opportunity in Paris! Join us at @geosciences.bsky.social to study how magma reservoirs beneath mid-ocean ridges pressurize and trigger eruptions. Part of the @erc.europa.eu #SeaSALT project with strong international links. Background in (geo)physics? Apply now! tinyurl.com/yupkweya

Volcanic Eruption in Deep Ocean Ridge Is Witnessed by Scientists for First Time Researchers diving in a submersible in the eastern Pacific realized that the landscape they had studied the day before had been glassed over by fresh lava.

🧪⚒️ The New eruption @ the East Pacific Rise after a cycle of melt accumulation & seafloor uplift. Several years of follow up by Thibaut Barreyre (CNRS@GeoOcean) & coPIs will tell how these events build the oceanic crust, 1 eruption @ a time - & comeback of ecosystems

www.nytimes.com/2025/05/02/s...

Volcanic Eruption in Deep Ocean Ridge Is Witnessed by Scientists for First Time (Gift Article) Researchers diving in a submersible in the eastern Pacific realized that the landscape they had studied the day before had been glassed over by fresh lava.

**BIG NEWS in the geology world!** For the first time, scientists spotted an active eruption along the mid-ocean ridge!!

They visited the hydrothermal vent the day before, where a vibrant ecosystem thrived in the sweltering water. The next day, everything was gone. ⚒️🧪

My latest for @nytimes.com

[RDV 16h !] A la fin du XXe siècle, les travaux de l’océanographe Marie Tharp ont bouleversé la géologie et notre connaissance de la tectonique des plaques. Quelles furent ces découvertes et leurs impacts ? tinyurl.com/26xwkx4y avec @jescartin.bsky.social, Cécile Prigent et Laurent Jolivet

Schematic illustration of the OHA-GEODAMS seafloor observatory. Credit: J.-A. Olive (LG-ENS) & J.-Y. Royer (Geo-Ocean)

If it all goes well, our now-complete observatory will be the first to document seafloor spreading and transform faulting events with geodesy, hydro-acoustics, and seismology! 🤞

An A-0-A pressure sensor, encased in a frame attached to four buoys floating on the ocean surface, waiting to be picked up. Credit: J.-A. Olive, LG-ENS / FOF

Last, but not least, we also recovered and re-deployed an A-0-A pressure sensor, right in the middle of the ridge's axial valley. This state-of-the-art instrument corrects its own drift by regularly re-calibrating itself against an inner chamber where the pressure is known.

watching the seafloor spread

a hydrophone encased in an orange float just surfaced right in front of the R/V Marion Dufresne, on a calm sea. Credit: J.-A. Olive, LG-ENS / FOF

We also recovered and redeployed five hydrophones that were first deployed last year during the #GEODAMS 2024 cruise.

Regional map of the Southeast Indian Ridge near Amsterdam Island

For the last ~10 days, we've been hard at work on and around the Southeast Indian Ridge at 37ºS to recover and redeploy a bunch of geophysical instruments. Let's break it down 👇

and… welcome back!

sunrise on the Indian ocean seen from the starboard side of R/V Marion Dufresne

sunset on the Indian ocean seen from the back deck of R/V Marion Dufresne

4-8 watch best watch

⚒️🧪🌊 25/25 -The #VG2024 leader completed the race after 64j19h22 at 17.8 knots. More than 26700 nm (~51000 km) crossing 4 major mid-ocean ridges (Mid-Atlantic, Southwest, South East & East Pacific Rise) & around Antarctica. Thnks to @jie-chen.bsky.social for the Spilhaus map: doi.org/10.1038/s415...

off you go, Glidy! come back with lots of 🐋 sounds

Julie & Jean-Arthur bringing the glider to the workboat for deployment. Credit: E. Klein

A few days ago, we deployed a Sea Explorer glider developed by ALSEAMAR and owned by ENSTA Bretagne at the location of our first hydrophone, southeast of Amsterdam island.

Data coming live from the ship's multibeam echosounder

As we make our way to our study area, we map the seafloor under the ship! 🌊 Our multibeam echosounder sends acoustic waves to the ocean floor and records how much time they take to bounce back.

@jbeesau.bsky.social carefully applying an official Marion Dufresne stamp on the mail. Credit: C. Dimier

the official OHA-GEODAMS 2025 stamp: an illustration of our seismo-geodetic network across the mid-ocean ridge + the glider listening to whale sounds. Credit: J.-Y. Royer

A tradition aboard the Marion Dufresne is to stamp letters to be mailed from the French Southern and Antarctic Lands. The ship captain, chief mechanic, doctor... each have their own stamp, and the science teams make new, custom ones every year!

⚒️🧪🌊 24/n - & the #VG2024 lead is near King's Trough, a failed rift formed perpendicular to the ridge axis 40 to 25 Myrs ago, now fossilised. First named by Laughton in '65 and described in detail by Matthews et al. in '69, the rift is a few km deep, and reaches 6000 m bsl @ Keep Deep to the East.

big wave crashing against the prow of R/V Marion Dufresne. Credit: S. Furst

barometer highlighting the low-pressure zone (965 hPa) we just went through. Credit: S. Furst

Kerguelen island in the distance. Credit: J.-A. Olive

We're back in business after a rough storm west of Kerguelen! We're now sheltered from the waves (but not the wind!) in the Gulf of Morbihan, enjoying our first views of the island and prepping the logistics of next week's deployments.

⚒️🧪🌊 23/n - The #VG2024 sailed over Great Meteor Guyot - part of a set of hotspot seamounts formed 20 to Myrs ago, possibly linked to the Azores hotspot to the N. The Guyot is flat topped due to wave erosion & later subsidence. It was 1st mapped & named during the N Atlantic Meteor cruise in 1937.

i mean, the storm was bad, but not rise-of-skywalker bad

our regularly scheduled @geodams.bsky.social programming will resume when the ship returns to a more horizontal position

Group picture of the GEODAMS 2025 team, on the deck of R/V Marion Dufresne, in front of Crozet Island

Meet the #GEODAMS 2025 team! ⚒️ @earth-science.bsky.social Right to left, back to front 👇

but none can beat Björk youtu.be/-WnzRqCK6Fs?...

black-browed albatross. Credit: Julie Béesau

white-chinned petrel. Credit: Julie Béesau

yellow-billed albatross. Credit: Julie Béesau

giant petrel. Credit: Julie Béesau

For several days now, several species of seabirds have been making their way with us. We've seen: the great albatross, the sooty albatross, yellow-billed albatross, black-browed albatross, giant petrels, white-chinned petrels and many others whose identification is not always easy.

the perks of the Furious Fifties