A type of volcanic crater called a caldera forms when a large eruption drains a magma chamber beneath a volcano, causing the ground to collapse. These eruptions can eject anywhere from 10 km3 to over 1,000 km3 of magma, devastating the local area and sometimes cooling the entire planet.
One of the root causes of all this activity could be the age of the lithosphere, that ever-spreading, always-moving seafloor crust. “South of eastern Java,” Dr Dyment said, pointing to a brightly coloured map on his computer, “the lithosphere is about 120 million years old. South of western Java, it’s younger, maybe 80 million years old. But alongside Sumatra, the crust is much younger, as young as 45 million years old. And then, of course, on the other side of that, things start aging again.
Between roughly 84 and 118 million years ago, during the Cretaceous Period, north was north and south was south, just like it is today. But around 83 million years ago, the planet’s polarity reversed, which means if you had been alive at that time and had held a compass in the palm of your hand, the north needle would have pointed south. Since then, the Earth’s polarity has reversed more than 40 times, sometimes for stretches lasting millions of years, other times for comparatively short slivers of geological time. Long or short, the records of these changes on the seafloor are known as magnetic anomalies.
Yesterday afternoon, at Captain Victor Broi’s suggestion, I went up to the bridge to watch Navigation Officer Mr Turcu Lucian and Helmsman Mr Dumitrache Lucian (no relation), execute a rather complicated series of turns that would allow us to pass over the first coring site three times from three different directions.
For students participating in the MIRAGE, every day is an opportunity to learn something new. For example, when entering data into the log book, it is an opportunity to go beyond the numbers and learn—in real time—what those numbers mean. Similarly, when students are cleaning up the bathymetry (the underwater study of the terrain of the ocean floor), attending the daily 4pm meeting, or dining with a member of the Institut Paul Emile Victor (IPEV) who they have not yet spoken with, they are free to soak up as much new information as they like.
Tectonics Group Leader of the Earth Observatory of Singapore (EOS), Professor Paul Tapponnier, made an appearance on Channel NewsAsia last Friday on 1 July 2016.
When I spoke with Captain Victor Broi the other morning, he mentioned that one of the biggest challenges facing his crew on this voyage was keeping everyone happy when it comes to food. In particular, he cited the need to prepare a special pre-dawn breakfast for those passengers observing Ramadan, the month-long period (it ended yesterday on Wednesday) when Muslims fast during daylight hours.
As the captain of the R/V Marion Dufresne, Captain Victor Broi is new to research vessels, but that doesn’t mean the 57-year-old seaman (whose birthday is today) lacks experience. Though the MIRAGE is only his second voyage as the captain of the Marion Dufresne, Capt Broi has spent his entire career with CMA CGM, a French container transportation and shipping company that manages the Marion Dufresne, as well as one of the largest fleets of container ships in the world.
Although a number of seafloor samples will be cored towards the end of our four-week expedition, the main data-acquisition instruments aboard the research vessel Marion Dufresne are an echosounder and a sub-bottom profiler, both mounted on a gondola attached to the ship’s hull. These two instruments will produce the bathymetry that is so essential to the mission of the MIRAGE.