It looks like the Eye of Sauron from Lord of the Rings trilogy, an ancient underwater volcano was slowly discovered by multi-beam sonar 3,100 meters (10,170 feet) below our vessel, 280 kilometers (174 miles) southeast of Christmas Island.
It was the 12th day of our voyage exploring the Australian territories of the Indian Ocean, aboard the CSIRO, dedicated to ocean exploration, RV Researcher.
Previously unknown and unimagined, this volcano erupted from our screens as a giant oval depression called a caldera, whose width was 6.2 km by 4.8 km. It is surrounded by a rim 300 m high (resembling Sauron’s eyelids), and in its center is a conical peak 300 m high (‘pupil’).
Above: Sonar image of the volcano “Around Sauron” and the nearby underwater mountains on the seabed southwest of Christmas Island.
A caldera forms when a volcano collapses. The molten magma at the base of the volcano moves upward, leaving empty chambers. The thin solid crust on the surface of the dome then collapses creating a large crater-like structure. Often then a small new peak begins to form in the center as the volcano continues to eject magma.
One famous caldera is the one in Krakatoa, Indonesia, which exploded in 1883, killing tens of thousands of people, leaving only parts of the mountain edge visible above the waves. By 1927, a small volcano, Anak Krakatoa (“Child of Krakatoa”), had erupted in its center.
Conversely, we may not even be aware of volcanic eruptions when they occur deep under the ocean. One of the rare control signs is the presence of light rock rafts floating on the surface of the sea after being blown out of an underwater volcano. Eventually, this blue floods and sinks to the bottom of the ocean.
Our volcanic ‘eye’ was not just. Further mapping to the south revealed a smaller sea mountain covered with numerous volcanic cones, and even further to the south was a larger flat-topped submarine peak.
Following ours Lord of the Rings topic, we nicknamed them Barad-dûr (‘Dark Fortress’), or Ered Lithui (‘Ash Mountains’).
Although the knowledge of the author JRR Tolkien about mountain geology was not perfect, our names are brilliantly appropriate given the uneven nature of the first and the surface covered with the blue of the second.
Around Sauron, Barad-dur and Ered Lithui is part of a pile of submarine Karma mountains previously estimated by geologists to be more than 100 million years old and formed next to an ancient reef from the time Australia was located much further south, near Antarctica. .
The flat peak of Ered Lithui was formed by wave erosion when the sea level protruded above the sea surface, before the heavy sea peak slowly sank back into the soft bottom of the ocean. The top of Ered Lithui is now 2.6 km below sea level.
But here’s the geological puzzle. Our caldera looks surprisingly fresh for a structure that should be more than 100 million years old. Ered Lithui has nearly 100 m of layers of sand and mud coated over the top, created by the immersion of dead organisms over millions of years.
This sedimentation rate would partially clog the caldera. Instead, it is possible that the volcanoes continued to descend or that new ones formed long after the original foundation. Our restless Earth is never peaceful.
But life is adapting to these geological changes, and Ered Lithui is now covered with animals in the seabed. Fragile stars, starfish, crabs and worms bury themselves or glide across the sandy surface. Upright black corals, fans, sea whips, sponges and rods grow on the exposed rocks. Gelatinous eels spread around stone ravines and rocks. Batfish await unfortunate prey.
Our mission is to map the seabed and explore marine life from these ancient and secluded seascapes. The Australian government recently announced plans to create two massive marine parks across the region. Our expedition will provide scientific data to help Australian parks manage these areas in the future.
Scientists from museums, universities, CSIRO and Bush Blitz from Australia are taking part in the trip. We are nearing the end of the first part of the trip to the Christmas Island region. The second part of our trip to the Cocos Island region (Keeling) will be scheduled for the next year.
There is no doubt that many of the animals we find here will be new to science and our first records of their existence will be from this region. We expect many more surprising discoveries.
Tim O’Hara, senior curator of marine invertebrates, Victoria Museums.
This article was republished from an interview under a Creative Commons license. Read the original article.