why do volcanoes erupt in the ring of fire
The is a ring of volcanoes around the Pacific Ocean that result from subduction of oceanic plates beneath lighter continental plates. Subduction of oceanic. Most of the Earth's volcanoes are located around the Pacific Ring of Fire because that the location of most of the Earth's subduction zones. A subduction zone is a place where one plate of oceanic lithosphere (= the crust + uppermost
) is shoved under another plate. The downgoing plate is always the oceanic one. All while it was oceanic plate it collected water-saturated sediments and its uppermost few hundred meters got water saturated also. As it is shoved into the hotter mantle the plate heats up and all this water and other volatiles boil off and migrate upwards through the overlying plate. The addition of volatiles such as water to the hot overlying mantle causes partial melting and the production of. This magma rises up through the over-lying plate to erupt at the surface. If the overlying plate is a continent, you get a chain of volcanoes such as the Andes or Cascades.
If the overlying plate is ocean you get a chain of volcanic islands such as the Marianas or Aleutians. This is also where the Earth's deep ocean trenches are and where the Earth's deep earthquakes are. The trenches form because the downgoing plate is bent downward as it subducts. The earthquakes form as the two plates scrape against each other (earthquakes down to about 150 km) and then as the downgoing plate bends (earthquakes down to about 700 km). The earthquakes do a very good job of tracing the position of the downgoing plate. These zones of earthquakes are called Wadati-Benioff zones, after the two seismologists who first recognized them. Tens of thousands of people have had their lives disrupted in the past week by seismic and volcanic activity along the Ring of Fire. An earthquake off Alaska, an avalanche and volcanic eruption in central Japan and a volcano squirting lava in the Philippines all occurred within days of each other. It led the UN Office for Disaster Risk Reduction to. Many are asking whether there is cause for concern that something more serious might happen.
So is there reason to worry? The Ring of Fire refers to a string of volcanoes, earthquake sites and tectonic plates around the Pacific. It spreads across 40,000km (25,000 miles) from the southern tip of South America all the way to New Zealand. Roughly 90% of all earthquakes occur along the area and the ring is dotted with 75% of all active volcanoes on Earth, that's 452 individual active volcanoes. This week alone, The quake briefly triggered a tsunami warning for coastal areas of Alaska and British Columbia in Canada. On the same day, one soldier was killed and that may have been triggered by a volcanic eruption. The eruption of Mount Moto-Shirane, which is part of Mount Kusastsu-Shirane, also sent rocks raining down a kilometre-wide area near Kusatsu in central Japan, local media reported. Earlier last year, led to the closure of the city's international airport and forced up to 100,000 people to evacuate. Mount Sinabung, more than 3,000km away in Sumatra, Indonesia, had been dormant for 400 years before it began erupting again in 2010.
In 2016, at least seven people died after clouds of hot ash and gas. Sinabung began erupting again in 2017 and is still going. And Mount Kadovar, a volcano in Papua New Guinea, has been spewing ash for weeks, causing the evacuation of thousands of people from nearby islands. All are along the Ring of Fire. But Prof Chris Elders, a geology expert from Curtin University in Australia, says the recent activity is entirely normal. "There's nothing unusual about what we're seeing at the moment," he told the BBC. "It just so happens that these events are occurring at the same time in different parts of the region. There's not necessarily a relationship between them. " He says volcanic and tectonic activity has occurred in the region for "hundreds and thousands of years". "So if you're just looking at one tiny snapshot in such a long period of time it looks like it's something special that things are happening all at once, but if you stand back and look at it in the scale of things, you'll see the action is fairly continuous. " Dr Janine Krippner, a New Zealand volcanologist based in the US, tweeted that the zone was "not referred to as the Ring of Fire because it sits there doing nothing".
While there are fears that volcanoes are becoming more frequent, she said the rate of eruptions had "not recently increased". "We now have satellites to capture more eruptions, and the internet to talk about more eruptions," she said. , Mount Moto-Shirane had been quiet for 3,000 years before its sudden eruption. Does it mean anything that it has reawoken? Not really, says Prof Elders. "To us, 3,000 years is a long period to be inactive but if you look back at the history of the volcano over tens of thousands of years, you might see that that is quite regular for it," he said. "What you can say with confidence is that there will always continue to be earthquake and volcanic activity across different parts of the Ring of Fire. "
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