J.-A. Olive

⚠️New paper⚠️ Curious about the link between seafloor deformation, mush viscosity, and magma replenishment at #mid-ocean ridges? Check out our new paper on #EPR with @jaodynamics.bsky.social doi.org/10.1029/2026...

The news is out today in @nature.com ! The OHA-GEODAMS observatory had the incredible luck to capture a major seafloor spreading event back in 2024, just 2 months after its deployment. You can read all about it at: www.nature.com/articles/s41... Here’s how it unfolded 👇

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!

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)

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

🧪⚒️ 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...

**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

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! 🤞

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

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

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!

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

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.

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.

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.

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.

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

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

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

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

⚒️🧪🌊 21/n - The #VG2024 tracks N the S-wards path from a month ago, over the Equatorial Atlantic (posts 3-6). Here most transform zones link continental margins & the ridge axis, peristing tens of millions of years. Others form & disappear, transition to oblique offsets that migrate over time.

Today we were treated to spectacular views of Crozet's Possession Island and East Island, while the local penguins put on quite a show! 🐧🌤️⛰️

Crozet Island’s 🐧 welcoming committee never disappoints #OBSAustral2025 #GEODAMS

⚒️🧪🌊 20/n - #VG2024 sailing NE along the Brazilian coast, soon xssing the tracks of the start of VG2024. And sailing by the Vitoria Trinidad seamount chain, the track of the Trinidade hotspot. Volcanism is ~40 My near the coast, and at <500 kyrs at the Martin Vaz & Trinidad Islands to the East.

Happy new year from the R\V Marion Dufresne! Our journey began last year on xmas day, by heading straight South from La Réunion to the Crozet Islands.

The goal of #GEODAMS is to deploy and maintain the first-of-its-kind seafloor seismo-geodetic observatory across a mid-ocean ridge and adjacent transform fault, to document seafloor spreading as it happens on a time scale of a few years.

turns out the R/V Marion Dufresne is a spaceship

Did you know that there's an undersea volcano off of the Oregon/Washington coast? And did you know that's acting up? Let's unpack what this means, and what we know. 🧵

Hi! We are the OHA-GEODAMS team, a research project documenting how the Indian Ocean grows in (almost) real time. Between 2024 and 2027, we'll have 4 cruises to maintain a seafloor seismo-geodetic observatory across the Southeast Indian Ridge. We just started cruise #2, follow our adventures here!

Off to sea again! Another long journey across the Southern Indian Ocean to complete our #GEODAMS seismo-geodetic observatory on the Southeast Indian Ridge. Follow us at @geodams.bsky.social !

⚒️🧪🌊 17/n - #VG2024 lead crossed the Pacifc-Antarctic Ridge, south of the Nemo Point - farthest from land, some 2700 km from the nearest shore - & unmapped. The Fracture Zones here dissecting the ridge are named after some of the pioneers of marine geology - including Marie Tharp and Bruce Heezen.

Very grateful to have been awarded an #ERCCoG grant! The SeaSALT project aims at understanding how individual diking and fault slip events compete to accommodate extension at mid-ocean ridges… and end up shaping 2/3 of our planet’s surface. Stay tuned for future PhD/postdoc opportunities at ENS!

⚒️🌊 - 1/n - Today, 10th #VendeeGlobe 40 skippers sail from Sables d'Olonne: Atlantic, around Antarctica (Pacific & Indian oceans), back Atlantic. Will blog about marine geology & related topics following the race - till mid Jan if enough interest here. www.vendeeglobe.org/cest-quoi-le...

Hi there! My name is Jean-Arthur Olive, I’m a ☕️-fueled geodynamicist with a soft spot for mid-ocean ridges. My group and I study how brittle deformation of Earth’s lithosphere shape tectonic plate boundaries, from human to geological time scales.