Looks like the Eye of Sauron Lord of the Rings The trilogy was slowly revealed by multi-beam sonar, an ancient submarine volcano, 280 kilometers (174 mi) southeast of Christmas Island, 3,100 meters (10,170 ft) below our ship.
This was day 12 of our expedition to the Indian Ocean Territory of Australia aboard CSIRO’s private ocean research vessel RV. researcher.
This previously unknown and unimaginable volcano emerged from our screens as a giant oval-shaped depression called a caldera with a diameter of 6.2 km x 4.8 km. It is surrounded by a 300 m high frame (similar to Sauron’s eyelids) and at its center is a 300 m high cone-shaped hill (‘pupil’).
Above: Sonar image of the ‘Eye of Sauron’ volcano and nearby seamounts on the seabed southwest of Christmas Island.
A caldera is formed when a volcano collapses. The molten magma at the base of the volcano slides upward, leaving empty chambers. The thin solid crust on the surface of the dome then collapses, forming a large crater-like structure. Often, as the volcano continues to spew magma, a small new peak begins to form in the center.
A well-known caldera is the one at Krakatoa, Indonesia, which erupted in 1883, killing tens of thousands of people and leaving only a portion of the mountainside visible above the waves. In 1927, Anak Krakatoa (“Krakatoa’s child”) had grown, with a small volcano at its center.
On the contrary, we may not even be aware of volcanic eruptions occurring in the depths of the ocean. One of the few tell-tale signs is the presence of light pumice rafts floating on the sea surface after being blown out from a submarine volcano. Eventually, this pumice stone becomes clogged with water and sinks to the ocean floor.
Our volcanic ‘eye’ was not alone. Further mapping to the south revealed a smaller seamount covered with numerous volcanic cones, and further south a larger, flat-topped seamount.
our follow Lord of the Rings We named them Barad-dûr (‘Dark Fortress’) and Ered Lithui (‘Ash Mountains’) respectively.
While author JRR Tolkien’s knowledge of mountain geology is not perfect, our names are wonderfully appropriate given the rough nature of the former and the pumice-covered surface of the latter.
The Eye of Sauron, Barad-dûr and Ered Lithui are part of a Mixed cluster of seamounts that formed alongside an ancient sea ridge of Australia, previously estimated by geologists to be more than 100 million years old. It was located much further south, near Antarctica.
The flat summit of Ered Lithui was formed by wave erosion as the seamount rose above the sea surface before the heavy seamount slowly sank back to the soft ocean seafloor. The peak of Ered Lithui is currently 2.6 km below sea level.
But here is the geological riddle. Our caldera looks surprisingly fresh for a structure that must be more than 100 million years old. At the summit of Ered Lithui there are about 100 m of sand and mud layers formed by the sinking of dead organisms over millions of years.
This sedimentation rate would partially drown the caldera. Instead, it’s possible that volcanoes continue to sprout, or that new ones form long after the original foundation. Our Restless World is never motionless.
But life adapts to these geological changes, and Ered Lithui is now covered with animals on the seafloor. Brittle stars, starfish, crabs and worms burrow or slide onto the sandy surface. Upright black corals, fan corals, sea whips, sponges and mussels grow on exposed rocks. The gelatinous eel prowls around rock chutes and boulders. Batfish lurk for unsuspecting prey.
Our mission is to map the seafloor and study marine life from these ancient and secluded seascapes. The Australian government recently announced plans to create two large marine parks across the regions. Our expedition will provide scientific data to help Parks Australia manage these areas in the future.
Scientists from Australia’s museums, universities, CSIRO and Bush Blitz join the journey. We are about to complete the first part of our journey to the Christmas Island region. The second part of our journey to the Cocos (Keeling) Island area will be planned for next year.
No doubt many of the animals we will find here will be new to science and our first record of their existence will be from this region. Expect many more surprising discoveries.
Tim O’Hara, Senior Curator of Marine Invertebrates, Museums Victoria.
This article has been republished from The Conversation under a Creative Commons license. Read the original article.