St. Vincent’s southern volcanoes not likely to erupt – Scientist

By Demion McTair. Updated 6:45 p.m. Sunday, April 12, 2021, Atlantic Standard Time (GMT-4).

A photograph of the Grand Bonhomme Mountain, a topographic high of a former eruptive center of the Grand Bonhomme volcanic center.

Vol·ca·no – pronounced – väl-ˈkā-(ˌ)nō. The plural form of volcano is either volcanoes or volcanos – Marriam Webster Dictionary, Cambridge Dictionary, and Oxford Dictionary

Kingstown, St. Vincent: The volcanoes south of La Soufriere in St. Vincent “are all dead” and would not erupt in our lifetime, Geologist, Professor Richard Robertson said Sunday on radio.

Amid concerns about rumblings at La Soufriere being heard as far away as Kingstown, in the south, some 19.8 kilometers (12.3 miles) away, Professor Robertson said “the fact that you have the lightening and the rumbling close to you; Biabou, Mespo (Mesopotamia), [and] Kingstown, it don’t mean a volcano [is] erupting there”.

“The volcano is up in the north. The volcano is Soufriere and that is the only volcano that is going to be erupting, that has erupted,” Professor Robertson said, adding “don’t worry about the fact that something is going to break and open in the south, that has always been a thing that people think about,” Professor Robertson who is the lead scientist monitoring the La Soufriere volcano said.

“The fact is, St. Vincent’s volcano that’s erupting is in the north, the volcano that will erupt, that can erupt is in the north at La Soufriere. We know that because we have studied the rocks. We know that all the volcanos in the south, they are all dead. Volcanism migrated to the north; the old rocks are in the south, we know that from studies,” he added.

“Just like how I could speak here about what Soufriere is doing, based on our studies, I could tell you for sure that there is no volcano in the south and no place in the south that magma is going to punch through the surface anytime in our lifetime or probably anybody’s lifetime in the future, so don’t worry about that,” the experienced Geologist said.

According to website of the Seismic Research Center at The University of the West Indies, St. Augustine campus, St. Vincent has four (4) volcanic centers, three of which came before the LaSoufriere volcanic center.

Scientists believe that the island started out in the south where some of the oldest rocks in the country are found. The island’s development then progressed northwards over thousands of years until it reached where it is now at La Soufriere.

They believe that throughout the island’s history, there have been several volcanos and volcanic plugs remain today as relics of those old volcanos.

Here are St. Vincent’s three (3) volcanic centers before La Soufriere. All of the following information was take from the UWI Seismic Research Center’s website.

The Pre-Soufrière Volcanic centres of St. Vincent
The pre-Soufrière Volcanic centres of St. Vincent consists of the South-East Volcanics and the Grand Bonhomme and Morne Volcanic Centres (Robertson, 2003).

The South-East Volcanics is the most southerly geologic region on the island. It is a dissected landscape of rounded hills with low topography (<210 m), which extends from the Warrawarrow River in the west to the extensive Yambou lava flow in the east. The area is dominated by red scoriaceous basaltic spatter interbedded with and often overlying, massive to well-jointed basaltic lava flows, which are intruded by dykes. It contains the oldest rocks exposed on the island (2.74 ± 0.11 Ma; Briden, et al., 1979) and is mostly overlain by fine-grained yellow ash, which are correlated with late Pleistocene Yellow Tephra erupted by the Soufrière volcano (Hay, 1959, Rowley, 1978b). The youngest deposits exposed in the area are alluvial silt, sand and gravels found in the river valleys.

The Grand Bonhomme Volcanic Centre extends from Argyle to Colonarie in the east and Sion Hill Bay to Chateaubelair in the west. It is the largest geologic region on the island and is interpreted as a large stratovolcano with interbedded sequences of block and ash pyroclastic flow deposits, ashfall deposits, lava flows and subordinate domes. The landscape is heavily forested and the interior inaccessible and composed of deeply weathered lavas and volcaniclastic deposits. This volcanic centre is a composite of several eruptive centres that are now represented by the topographic highs of Grand Bonhomme (970 m), Petit Bonhomme (747 m), Mount St. Andrews (735 m) and an unnamed peak (1021 m). These peaks are central domes or plugs of volcanoes that coalesced to form a large composite volcanic centre. Previous dating of lavas from the western flank of the Grand Bonhomme Volcanic Centre by Briden et al (1979) obtained ages of 1.33 ± 0.09 and 1.18 ± 0.10 Ma respectively for lava flows at Westwood and Chateaubelair.

The Morne Garu Volcanic Centre occurs immediately to the north of Grand Bonhomme and consists of Mount Brisbane (932 m) to the east and Richmond Peak (1074 m) to the west. These two peaks are the remnants of an eroded Morne Garu crater or caldera that is estimated to have been 3 km in diameter (Sigurdsson, et al., in prep). Morne Garu is largely inaccessible and the underlying volcanics are extensively covered with fine-grained yellow ashfall deposits. Recent ages obtained by Heath et al. (1998, 1998) from lavas at Indian Estate (11 ± 14 ka) and Black Point (180 ± 20 ka) on the western flank of Mount Brisbane indicate that volcanism may have been much younger at this centre and may have overlapped with the Soufrière Volcano to the north. The major formations exposed are lava flows, undifferentiated volcaniclastics, red scoria bombs and yellow ashfall deposits. Reworked alluvial deposits occur in the major river valleys.

HOW DO YOU DETERMINE WHEN A VOLCANO IS DEAD?

According to Oregon State University, the definitions of the states of volcanos are not set in stone, and they mean different things to different people and to different volcanoes. One of the simpler ways to answer is that an active volcano is one that has erupted since the last ice age (i.e., in the past ~10,000 years).

That is the definition of active used by the Global Volcanism Program in their catalogs. A dormant volcano would then be one that hasn’t erupted in the past 10,000 years, but which is expected to erupt again. An extinct volcano would be one that nobody expects to ever erupt again, the university states on its website.

“These are human definitions of natural things – there have been a number of eruptions from “extinct” volcanoes!,” the university says.

At least two examples support the the view that volcanos once considered extinct came back to life. For instance, CNN reported in 2019 that a volcano in the far eastern corner of Russia that was previously considered extinct may be waking up — and an eruption could be catastrophic.

“The Bolshaya Udina volcano — part of the Kamchatka Peninsula’s Udina volcanic complex — was believed to be extinct until 2017, when increasing seismic activity was detected beneath it, scientists say,” CNN reported.

The National Geographic reported in 2019 that magma was found simmering under Romania’s Ciomadul volcano, which last exploded some 30,000 years ago, and scientist were trying to figure out why.

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