Antarctica's only active volcano shows how CO2 allows volcanoes to form persistent lava lakes at the surface

James Ross, Robert Scott, and Ernest Shackleton are just a few of the explorers who have made their mark on the land of mystery and heroic feats. A key piece of the puzzle for understanding global continental evolution is the example of the spectrum of Earth's volcanic processes. A study by the University of Utah and University of Canterbury New Zealand shows how CO 2 deep underground helps magma avoid being trapped deep in the Earth and allows it to reach and pool at the surface.

The study, published in Nature Communications, expands our understanding of the sources and transport of diverse types of magma and volatile gases to the surface.

Mount Erebus is an example of a CO 2 -dominated rift volcano, a complement to the more widely known arcs volcanoes of the Pacific Rim and elsewhere.

Understanding both H 2 O and CO 2 volcanoes is important for calculating the budget of such volatile gases deep in the earth that involve injection of material into Earth's mantle and its return to the surface.

The study was conducted with University of Utah alumni John Stodt and Michal Kordy, as well as associate scientist Virginie Maris and Paul Bedrosian of the United States Geological Survey. Danny Uhlmann is studying geology at the University of Lausanne and is one of the co-authors.

Those other volcanos.

Mount Erebus is the only active volcano in the world. Sir James Ross, who discovered the Transantarctic Mountains in 1841, named the volcano after him. Mount Erebus was first ascended by a party in 1908.

The lavas of Erebus are rich in some elements and poor in others, but they are an example of a family of volcanoes with an alkalic chemical composition.

Alkalic volcanoes are not the same as volcanoes in theCascade Range which extends from northern California through British Columbia to Alaska. In a place where the ocean is forced below the crust of the continent, the Cascades are found. The water in the rocks becomes part of the melt as the ocean crust sinks into the Earth, and is a volatile molecule that can be easily dissolved or evaporated.

As the pressure from the overlying crust decreases with ascent, the water in the evolving magma will not make it to the surface, like in the case of Mount St Helens in 1980 or Mount Lassen in 1912. At a depth of around three miles, the remaining magma stalls and freezes in place.

The volcano on Ross Island is in a continental rift zone. Earth's crust and mantle are pulled apart. Western Utah is an example of a rift zone. It is on the eastern boundary of the Great Basin geological province and is being slowly stretched east-west. Erebus is located along the margin of the West Antarctic Rift System and has been for tens of millions of years.

The rift zone's magmas have volatiles from the recycling of ocean crust and are liberated to the surface through the process. The volatiles in these magmas are dominated by CO 2

A classic feature of an evolved, CO 2 -rich rift volcano is a persistent lava lake. There must be something about rift volcanoes that allows magma to reach the surface relatively peacefully, because lava lakes are not found in arcs like theCascades.

The Magma is being photographed within the Earth.

It is impractical to collect samples of rocks from depths of more than a few kilometers beneath the surface. This is similar to the scans of the human body. Sound waves are used for internal scans in the most popular and widely applied geophysics. This is used in exploration for oil and gas. Natural seismic sources that can reach deep into the Earth are sparse around Erebus volcano, and images using such have only been derived to shallow depths.

They used a method called magnetotelluric sounding. Natural waves generated by the sun and lightning are used to make a sound. Most of the waves travel through the air, but they scatter off rock structures of interest and return to the surface, where we can measure them using sophisticatedvolt meters.

Depending on the extent to which rock and other material conducts or resists electricity, the waves travel faster or slower. Magma can be detected by this technique.

This is not the first time that the group has traveled to the South Pole. The technique of high-fidelity magnetotelluric measurements on polar ice sheets was pioneered by them. In addition to studies at the South Pole and Central West Antarctica, Wannamaker led a multi-season campaign across the Central Transantarctic Mountains showing how those mountains were uplifted. Their technique is being used by other researchers.

In the last three years, Wannamaker and colleagues have measured at more than 100 sites on Erebus Ross Island. Patterns of backscattered radiation from all the stations were used to create a computer program that could create an image of Earth's upper mantle through the island and volcano to a depth of about 100 kilometers.

The data shows a steep conduit of low electrical resistivity coming from the upper mantle. The conduit takes a pronounced turn in the deep crust before reaching the summit lava lake. The rock type formed by Erebus is called Phonolite.

The magmatic valve is formed by intersecting north-south and east-west faults, since the area around Erebus is known to have faults in the same east-west orientation.

Unlike the H 2 O-rich arcs of the Pacific Rim, the CO 2 dominated Erebus shows the structures that allow magma to rise right to the volcano.

The scales and volumes of volatile transport in the Earth are revealed by understanding transport controls and pathways for this type of volcano.

More information: Trans-crustal structural control of CO2-rich extensional magmatic systems revealed at Mount Erebus Antarctica, Nature Communications (2022). DOI: 10.1038/s41467-022-30627-7 Journal information: Nature Communications Citation: Antarctica's only active volcano shows how CO2 allows volcanoes to form persistent lava lakes at the surface (2022, May 30) retrieved 30 May 2022 from https://phys.org/news/2022-05-antarctica-volcano-co2-volcanoes-persistent.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.