(ORDO NEWS) — Erebus is the only active volcano in Antarctica, located on Ross Island. In its mouth there is always a lava lake, which is a rarity for volcanoes. In a new study, geologists have found that the Erebus lava lake exists thanks to the abundance of carbon dioxide in the mantle below it.
Antarctica and its environs are rich in all sorts of wonders and mysteries, many of which scientists have yet to unravel. This is an ice sheet several kilometers thick, which slowly flows and gives rise to floating ice, and subglacial freshwater lakes, and paleontological evidence of ancient life on the continent.
Erebus is also in Antarctica – an active volcano with a height of 3794 meters. More precisely, it is located on the small island of Ross, near the coast of the icy continent, together with several extinct volcanoes. Erebus has been active for a very long time and constantly emits various gases.
An unusual volcano in the middle of glaciers is an interesting object for geologists, and not only. By studying Erebus , one can learn a lot about volcanism in general and even about the evolution of continents.
Now, the joint efforts of scientists from the University of Utah (USA) and the University of Canterbury (New Zealand) have helped to find out why the magma under Erebus does not remain at depth, but pours out to the surface (becoming lava) and forms a stable lake.
“Mount Erebus is an example of a carbon dioxide-dominated rift volcano, a good addition to the well-studied island arc volcanoes of the Pacific Ring of Fire and other areas, as they are dominated by water vapor,” said one of the authors of a new paper in Nature Communications . Graham Hill.
Geologists are convinced that an understanding of the processes occurring inside both types of volcanoes – both rich in carbon dioxide and saturated with water vapor – is necessary to assess the balance of these volatile gases on Earth.
The gas exchange of the mantle with the surface of the planet is affected by both the penetration of the material of the earth’s crust into the depths and the return of matter to the outside.
So, Erebus, the only active volcano in Antarctica, also belongs to the special “carbon dioxide” volcanoes. But this is not the most surprising: in its crater there is always a lava lake with a diameter of 250 meters. Stable lava lakes are rare: they are characteristic of only a few of the more than 1300 terrestrial volcanoes.
The authors of the new article managed to find a connection between these two features of Erebus. It turns out that its lava lake is maintained precisely by the flows of carbon dioxide in the magma.
Magma (viscous, fluid and very hot material of the mantle) is constantly mixed by convection, forming huge updrafts – plumes . Rising magma is able to come to the surface, but it does not always succeed.
The fact is that the enormous pressure of the lithosphere drops sharply as it approaches the surface, due to which water is released from the magma. The remnants of the magma stop without appearing in the mouth of some volcano – as a rule, at a depth of about five kilometers.
It is very difficult to study what is happening in the deep parts of the earth’s crust and in the mantle directly. To get samples from such a depth is an unrealistic task. In such cases, geophysical methods come to the aid of scientists.
They are like a CT scan, which allows you to look inside a person without harming him. Among geophysical methods, seismoacoustic methods are especially popular – in this case, the property of rocks is judged by the transmission or reflection of a sound wave by them. They are used, in particular, in oil and gas exploration.
However, there are few natural sources of seismic activity in the vicinity of Erebus, so seismoacoustics does not work well. Therefore, scientists turned to another method of geophysics – magnetotelluric sounding.
It is based on the detection of natural electromagnetic radiation, which is created by the Sun and lightning discharges.
Most of these electromagnetic waves propagate only in the air, but some still penetrate the Earth, interact with rocks and return to the surface, where geologists armed with specially designed voltmeters await them.
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