2023-11-14 12:00:05
In the Pacific Ocean, a remarkable natural phenomenon occurred recently: an underwater volcano, located near the island of Iwo Jima in Japan, gave birth to a new island (see our news on this subject) .
The new volcanic island visible in satellite images after its emergence from the ocean near the Japanese island of Iwo Jima (IĹŤjima or IĹŤtĹŤ (硫黄島, IĹŤjima or IĹŤtĹŤ?…).
Image credit: ESA/USGS
This underwater volcanic eruption, which began on October 21, saw its activity intensify over the days. Ten days later, huge explosions were occurring every few minutes, propelling large masses of rock into the air. as well as a jet of gas and ash that rose more than 50 meters above the surface of the water.
Volcanic ash and accumulated rocks formed this new island, now visible from space thanks to Landsat 9 satellite images, captured on November 3. These images show a before and after of the recent eruption about 1,200 km south of Tokyo.
This phenomenon also produced a sea of ​​floating pumice, an extremely porous rock typical of explosive eruptions. Recent analyzes have revealed that the chemical composition of this pumice differs from that of other volcanoes in this chain. It would come from an eruption along the back-arc rift zone, behind a volcanic arc.
Setsuya Nakada / Asahi Shimbun
The current eruption occurred in almost the same location as another in July 2022, suggesting a resumption of magmatic activity on Iwo Jima. Yuji Usui, an analyst with the Japan Meteorological Agency, confirmed that the eruption is now over.
The newly formed island, measuring approximately 100 meters wide and 20 meters high, appears to be shrinking as waves erode the crumbly rock. Its sustainability depends on its composition: if it is mainly made up of lava, it could exist longer. “We just have to observe its evolution,” said Yuji Usui.
Underwater volcanic eruption: very different from terrestrial eruptions
An underwater volcanic eruption is a geological phenomenon where a volcano located beneath the ocean surface erupts. Unlike terrestrial volcanoes, underwater volcanoes expel their magma, gas, and ash directly into seawater. (Seawater is the salt water of Earth’s seas and oceans.). This unique interaction between hot magma and cold water has several important consequences. First, seawater quickly cools the magma, which often results in the formation of new specific volcanic rocks, such as pumice or pillow basalt. These rock formations are characterized by their particular texture, due to the rapid solidification of magma in contact with water.
In addition, the pressure exerted by seawater on the volcano influences the type of eruption. Underwater eruptions can be less visually spectacular than their terrestrial counterparts, because the immense pressure of the water partly contains the force of the explosion. (An explosion is the rapid transformation of one material into another material having a …). However, they can still be extremely powerful and are capable of creating new islands or significantly altering the seabed.
Finally, underwater volcanic eruptions play a crucial role in Earth’s geology. They contribute to the creation of new underwater reliefs and can significantly influence the marine ecosystem by modifying the chemistry of water and by providing new habitats for marine life.
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