Credit score: Phil Vandenbossche & Nelson Kuna/CSIRO
Wanting just like the Eye of Sauron from the Lord of the Rings Trilogy, an historical undersea volcano was slowly revealed by multibeam sonar 3,100 meters under our vessel, 280 kilometers southeast of Christmas Island. This was on day 12 of our voyage of exploration to Australia’s Indian Ocean Territories, aboard CSIRO’s devoted ocean analysis vessel, the RV Investigator.
Beforehand unknown and unimagined, this volcano emerged from our screens as a large oval-shaped despair referred to as a caldera, 6.2km by 4.8km throughout. It’s surrounded by a 300m-high rim (resembling Sauron’s eyelids), and has a 300 m excessive cone-shaped peak at its middle (the “pupil”).
Sonar picture of the ‘Eye of Sauron’ volcano and close by seamounts on the ocean mattress south-west of Christmas Island. Credit score: Phil Vandenbossche & Nelson Kuna/CSIRO
A caldera is fashioned when a volcano collapses. The molten magma on the base of the volcano shifts upwards, leaving empty chambers. The skinny stable crust on the floor of the dome then collapses, creating a big crater-like construction. Usually, a small new peak then begins to kind within the middle because the volcano continues spewing magma.
One well-known caldera is the one at Krakatoa in Indonesia, which exploded in 1883, killing tens of 1000’s of individuals and leaving solely bits of the mountain rim seen above the waves. By 1927, a small volcano, Anak Krakatoa (“little one of Krakatoa”), had grown in its middle.
In distinction, we might not even concentrate on volcanic eruptions after they occur deep beneath the ocean. One of many few tell-tale indicators is the presence of rafts of sunshine pumice stone floating on the ocean floor after being blown out of a submarine volcano. Finally, this pumice stone turns into waterlogged and sinks to the ocean ground.
Our volcanic “eye” was not alone. Additional mapping to the south revealed a smaller sea mountain lined in quite a few volcanic cones, and additional nonetheless to the south was a bigger, flat-topped seamount. Following our Lord of the Rings theme, we’ve got nicknamed them Barad-dûr (“Darkish Fortress”) and Ered Lithui (“Ash Mountains”), respectively.
The voyage of the RV Investigator round Christmas Island. Credit score: Tim O’Hara/Museums Victoria
Though writer J.R.R. Tolkein’s information of mountain geology wasn’t excellent, our names are splendidly applicable given the jagged nature of the primary and the pumice-covered floor of the second.
The Eye of Sauron, Barad-dûr, and Ered Lithui are a part of the Karma cluster of seamounts which have been beforehand estimated by geologists to be greater than 100 million years previous, and which fashioned subsequent to an historical sea ridge from a time when Australia was located a lot additional south, close to Antarctica. The flat summit of Ered Lithui was fashioned by wave erosion when the seamount protruded above the ocean floor, earlier than the heavy seamount slowly sank again down into the gentle ocean seafloor. The summit of Ered Lithui is now 2.6km under sea stage.
However right here is the geological conundrum. Our caldera seems to be surprisingly recent for a construction that ought to be greater than 100 million years previous. Ered Lithui has nearly 100m of sand and dust layers draped over its summit, fashioned by sinking lifeless organisms over thousands and thousands of years. This sedimentation fee would have partially smothered the caldera. As an alternative it’s doable that volcanoes have continued to sprout or new ones fashioned lengthy after the unique basis. Our stressed Earth is rarely nonetheless.
The big deep-sea predatory seastar Zoroaster. Credit score: Rob French/Museums Victoria
However life adapts to those geological modifications, and Ered Lithui is now lined in seafloor animals. Brittle-stars, sea-stars, crabs, and worms burrow into or skate over the sandy floor. Erect black corals, fan-corals, sea-whips, sponges, and barnacles develop on uncovered rocks. Gelatinous cusk-eels prowl round rock gullies and boulders. Batfish lie in look ahead to unsuspecting prey.
Small batfish patrol the seamount summits. Credit score: Rob French/Museums Victoria
Our mission is to map the seafloor and survey sea life from these historical and secluded seascapes. The Australian authorities lately introduced plans to create two large marine parks throughout the areas. Our expedition will provide scientific information that can assist Parks Australia to handle these areas into the long run.
Elasipod sea cucumbers feed on natural detritus on deep sandy seafloors. Credit score: Rob French/Museums Victoria
Scientists from museums, universities, CSIRO and Bush Blitz round Australia are collaborating within the voyage. We’re near finishing half certainly one of our journey to the Christmas Island area. Half two of our journey to the Cocos (Keeling) Island area will probably be scheduled within the subsequent 12 months or so.
Little question many animals that we discover right here will probably be new to science and our first data of their existence will probably be from this area. We anticipate many extra shocking discoveries.
Written by Tim O’Hara, Senior Curator of Marine Invertebrates, Museums Victoria.
Initially printed on The Dialog.