Seamounts off the coast of Antarctica have puzzled volcanologists and geologist as to their origin. As a result of new findings at the Marie Byrd Seamounts in the Amundsen Sea which was published yesterday in the scientific journal “Gondwana Research”, the submarine chain of…
Seamounts off the coast of Antarctica have puzzled volcanologists and geologist as to their origin. As a result of new findings at the Marie Byrd Seamounts in the Amundsen Sea which was published yesterday in the scientific journal “Gondwana Research”, the submarine chain of volcanoes is the result of “mantle plumes”.
Scientists from GEOMAR Helmholtz Centre for Ocean Research Kiel in cooperation with colleagues from the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research just published possible explanations for the origin of these former volcanoes and thus contributed to the decryption of complex processes in the Earth’s interior. Because the Marie Byrd seamounts are very difficult to reach with conventional research vessels, they have hardly been explored.
Several seamounts do not fit any of the usual models for the formation of volcanoes. Classic volcanologists differentiate between two types of volcanic formations. One type is generated where tectonic plates meet producing a fissure or crack in the Earth’s crust. The other type is formed within the Earth’s plates where super-heated melted rocks or magma rises from the Earth’s outer core melting its way via convection through the mantle and lithosphere then punctures a gap in the Earth’s crust.
When this occurs along the ocean bottoms they are called seamounts. When occurring on dry land they are known as a volcanic range. Most mantle plumes are located on the sea floors, not a surprise with 2/3 of Earth covered by oceans. But mantle plumes are also located on land in areas around the world. The most famous and notorious mantle plume is Yellowstone super-volcano. As you can see from the graphic below, the vast amount of magma is located deep within the Earth – all the way to the outer core.
In 2006, a team of scientists aboard the research vessel ‘Polarsten’ in the Amundsen Sea, salvaged rock samples from the seamounts and subjected these to thorough geological, volcanological and geochemical investigations after returning to the home labs. “Interestingly enough, we found chemical signatures that are typical of plume volcanoes. And they are very similar to volcanoes in New Zealand and the Antarctic continent,” says geochemist Dr. Folkmar Hauff, second author of the paper.
Based on this finding, the researchers sought an explanation. They found it in the history of tectonic plates in the southern hemisphere. Around 100 million years ago, remains of the former supercontinent Gondwana were located in the area of present Antarctica. A mantle plume melted through this continental plate and cracked it open. Two new continents were born: the Antarctic and “Zealandia”, with the islands of New Zealand still in evidence today. When the young continents drifted in different directions away from the mantle plume, large quantities of hot plume material were attached to their undersides. These formed reservoirs for future volcanic eruptions on the two continents. “This process explains why we find signatures of plume material at volcanoes that are not on top of plumes,” says Dr. Hauff.
“Continental tectonic plates are thicker than the oceanic ones. This ensures, among other things, differences in temperature in the underground,” says volcanologist Dr. Werner. And just as air masses of different temperatures create winds, the temperature differences under the Earth’s crust generate flows and movements as well. Thus the plume material that once lay beneath the continent was able to shift under the oceanic plate. With disruptions due to other tectonic processes, there were cracks and crevices which allowed the hot material to rise, turn into magma and then- about 60 million years ago – allowed the Marie Byrd Seamounts to grow. “This created islands are comparable to the Canary Islands today,” explains Andrea Kipf.
Based on the previously little investigated Marie Byrd Seamounts, the researchers were able to show another example of how diverse and complex the processes are, that can cause volcanism. “We are still far from understanding all of these processes. But with the current study, we can contribute a small piece to the overall picture,” says Dr. Werner.