How volcanoes explode in the deep sea

Date:
June 29, 2020
Source:
University of Wu"rzburg
Summary:
Explosive volcanic eruptions are possible deep down in the sea -
- although the water masses exert enormous pressure there.



FULL STORY ==========================================================================
Most volcanic eruptions take place unseen at the bottom of the world's
oceans.

In recent years, oceanography has shown that this submarine volcanism
not only deposits lava but also ejects large amounts of volcanic ash.


==========================================================================
"So even under layers of water kilometers thick, which exert great
pressure and thus prevent effective degassing, there must be mechanisms
that lead to an 'explosive' disintegration of magma," says Professor
Bernd Zimanowski, head of the Physical-Volcanological Laboratory of Julius-Maximilians-Universita"t (JMU) Wu"rzburg in Bavaria, Germany.

Publication of an international research group An international research
group led by Professors James White (New Zealand), Pierfrancesco Dellino (Italy) and Bernd Zimanowski (JMU) has now demonstrated such a mechanism
for the first time. The results have been published in the journal
Nature Geoscience.

The lead author is Dr. Tobias Du"rig from the University of Iceland, a JMU alumnus and former Ro"ntgen Award winner of the JMU Institute of Physics.

Before he went to Iceland, Du"rig was a member of the research groups
of Professor Zimanowski and Professor White.

Diving robot sent to a depth of 1,000 metres The team did research at
the Havre Seamount volcano lying northwest of New Zealand at a depth of
about 1,000 metres below the sea surface. This volcano erupted in 2012,
and the scientific community became aware of it.



==========================================================================
The eruption created a floating carpet of pumice particles that expanded
to about 400 square kilometres -- roughly the size of the city of
Vienna. Now a diving robot was used to examine the ash deposits on the
seabed. From the observational data the group of James White detected
more than 100 million cubic meters of volcanic ash.

The diving robot also took samples from the seafloor, which were then used
in joint experimental studies in the Physical-Volcanological Laboratory
of JMU.

Experiments in the Physical-Volcanological Laboratory "We melted
the material and brought it into contact with water under various
conditions. Under certain conditions, explosive reactions occurred
which led to the formation of artificial volcanic ash," explains Bernd Zimanowski. The comparison of this ash with the natural samples showed
that processes in the laboratory must have been similar to those that
took place at a depth of 1,000 meters on the sea floor.

Zimanowski describes the decisive experiments: "In the process, the molten material was placed under a layer of water in a crucible with a diameter
of ten centimeters and then deformed with an intensity that can also be expected when magma emerges from the sea floor. Cracks are formed and
water shoots abruptly into the vacuum created. The water then expands explosively. Finally, particles and water are ejected explosively. We
lead them through an U-shaped tube into a water basin to simulate the
cooling situation under water." The particles created in this way, the "artificial volcanic ash," corresponded in shape, size and composition
to the natural ash.



========================================================================== Possible effects on the climate "With these results, we now have a much
better understanding of how explosive volcanic eruptions are possible
under water," says the JMU professor. Further investigations should also
show whether underwater volcanic explosions could possibly have an effect
on the climate.

"With submarine lava eruptions, it takes a quite long time for the heat of
the lava to be transferred to the water. In explosive eruptions, however,
the magma is broken up into tiny particles. This may create heat pulses so strong that the thermal equilibrium currents in the oceans are disrupted locally or even globally." And those very currents have an important
impact on the global climate.

Volcanoes on the ocean floor There are around 1,900 active volcanoes
on land or as islands. The number of submarine volcanoes is estimated
to be much higher. Exact numbers are not known because the deep sea
is largely unexplored. Accordingly, most submarine volcanic eruptions
go unnoticed. Submarine volcanoes grow slowly upwards by recurring
eruptions. When they reach the water surface, they become volcanic islands
-- like the active Stromboli near Sicily or some of the Canary Islands.


========================================================================== Story Source: Materials provided by University_of_Wu"rzburg. Original
written by Robert Emmerich. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. T. Du"rig, J. D. L. White, A. P. Murch, B. Zimanowski, R. Bu"ttner,
D.

Mele, P. Dellino, R. J. Carey, L. S. Schmidt &
N. Spitznagel. Deep-sea eruptions boosted by induced
fuel-coolant explosions. Nature Geoscience, June 2020 DOI:
10.1038/s41561-020-0603-4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200629120135.htm

--- up 22 weeks, 6 days, 2 hours, 38 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)