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Tonga Underwater Volcano That Shakes Half the World

  A huge mushroom cloud rose rapidly from the sea, and shock waves from the eruption of the underwater volcano resounded through the sky. Although many Tongans were mentally prepared for a volcanic eruption before, they did not expect that this underwater volcanic eruption would be so sudden and violent…
A quick interpretation of the Tonga volcanic eruption

  Where is Tonga? Tonga is located in the South Pacific, and the shortest straight-line distance from Australia is more than 3,300 kilometers. Its capital, Nuku’alofa, is located on the main island, Tongatapu Island.
  The whole process of the volcanic eruption On December 20, 2021, the submarine volcano on Aha Apai Island in Tongahun spewed ash. At 2:00 the next day, the volcanic eruption ended. The brief and mild eruption did not attract special attention from scientists who study the volcano. On January 11, 2022, the Tonga submarine volcano was deemed to have gone dormant again. However, the volcano erupted again on January 14, 2022, and suddenly and violently erupted on the 15th.
  Although the eruption lasted only 8 minutes, it became one of the most violent volcanic eruptions in the world in 30 years (explosion index 5), second only to the 1991 eruption of Mount Pinatubo in the Philippines (index 6).
  Where is the crater The crater of this eruption is 65 kilometers away from the main island of Tonga. The island was originally two separate islands, one of which was called Hong Atanga and the other was called Hong Aha Apai. In late 2014, a large amount of magma erupted from the crater below the two islands, connecting the two islands into one. As of the end of the eruption on January 15, 2022, the top of the remaining crater was 700 meters above the sea surface and had a diameter of 6 to 7 kilometers.
  Has Tonga gone? It is estimated that the most violent explosion released the energy equivalent to 1,000 Hiroshima atomic bombs. Has Tonga disappeared under such a powerful outbreak? No. But most of the landmass of Hung A Tonga-Hoon Aha Apay Island was wiped from the sea by volcanic activity, leaving only a few reefs. The impact of the volcanic eruption on the main island of Tonga is mainly the damage caused by the tsunami to the coastal areas, as well as the impact of volcanic ash on the island’s transportation, communication and fresh water supply.
  Strong shock waves rang through the Pacific Ocean. In addition to Tonga, some pan-Pacific countries also heard the loud noise of the volcanic eruption. On the afternoon of the 15th, in Fiji, which is 800 kilometers away from the underwater volcano in Tonga, a resident suddenly heard a loud noise from outside his home. At first, he thought it was thunder, but soon the whole house began to vibrate, and the door was ping-pong. ring.

The island above the underwater volcano in Tonga (late 2014)

The actual crater is below the sea surface and has a huge cross-section

After the volcano erupted, the island nearly disappeared

  The shock wave from a volcanic eruption is still terrifying after traveling hundreds of kilometers. Residents of Anchorage, Alaska, and surrounding areas, about 9,700 kilometers from the volcano, heard a series of explosions that lasted 30 minutes, followed by low-frequency noise that lasted about two hours. Even Canada’s Yukon Territory, located in the Arctic Circle, reported hearing the explosion, with the shock wave reaching as far as 16,000 kilometers away in the United Kingdom.
Terror tsunami spread widely

  After the explosion, a tsunami followed. Tsunami waves swept through all the islands of Tonga. The tsunami that landed on the island exerted its destructive force, sweeping away everything in its path.
  An island resident said she was cooking dinner at home when the underwater volcano erupted when seawater suddenly poured into her home. “The ground shook and our house was shaking,” she recalled. “There were waves of loud noises and vibrations. My brother thought a bomb was going off nearby.” Her house was completely submerged in the sea, and her neighbor’s house collapsed. At that time, there were screams of people around, and people shouted hoarsely: “Run to the heights!”
  The people on the island were forced to move to higher ground, and the communication facilities in Tonga were completely destroyed, and the communication facilities connected to the outside world were completely destroyed. Undersea cables were also damaged. Soon, Tonga was completely lost.

  Affected by volcanic ash and tsunami, the island’s freshwater was heavily polluted. Authorities are calling on people to drink bottled water and wear masks to avoid volcanic ash from entering their lungs. The edges of volcanic ash particles are extremely sharp, and when fine particles of volcanic ash are inhaled into the lungs, they can cause irreversible damage to the lungs, or cause pulmonary fibrosis. series of questions. Volcanic ash also contains sulfur dioxide, which when dissolved in water forms toxic sulfuric acid.
  After the eruption of Tonga’s submarine volcano, the tsunami waves it triggered reached Australia, New Zealand, Japan and the west coasts of North and South America. The tsunami reached New Zealand five hours after the eruption and Alaska about 10 hours later; waves nearly 3 meters high were seen in parts of Japan; and in Peru, two people were killed by the tsunami waves.
  The destructive power of tsunami waves is far from that of ordinary waves. After a normal wave comes ashore, it can move forward for at most 15 seconds before returning to the sea; while the tsunami wave that hit the Australian coast continued to move ashore for 15 minutes, and then returned to the sea completely after another 15 minutes, causing confusion and huge losses.
  Why can the tsunami waves generated by Tonga’s submarine volcanic eruption cross the ocean and still cause varying degrees of damage after landing on the coasts of South America and other countries?
  Submarine landslides and changes in sea surface pressure caused by Tonga’s submarine volcanic eruptions are the two major causes of tsunamis. The wavelength of a tsunami is hundreds of kilometers. The longer the wavelength, the less likely it is to be affected by the unevenness or obstacles on the seabed surface, so the longer it travels. As the tsunami wave reaches the coastal area, the speed decreases, and the subsequent tsunami wave keeps catching up with the preceding tsunami wave. In this way, the tsunami waves are superimposed one by one, and when they reach the shore, a tsunami wave with a height of ten meters is formed.

  Why is there no tsunami report from China? In fact, China’s maritime monitoring department immediately detected the tsunami wave caused by the submarine volcano in Tonga, but when the tsunami wave reached China, it only caused a wave with a height of 20 centimeters.
Why did the explosion happen?

  The Tonga submarine volcano is located in the Pacific Rim volcanic-seismic belt and has erupted several times on a small scale between 2009 and 2021.
  Tonga’s submarine volcano takes 900 to 1,000 years to fill with magma, so the eruption has been described as a once-in-a-millennium eruption. As a large amount of magma cools and crystallizes, a large amount of gas accumulates inside the magma, causing the pressure inside the magma to gradually increase and the magma to become unstable. It’s like a bottle of champagne. Champagne is a sparkling wine. When filling champagne, workers add white sugar to the bottle, allowing the yeast to ferment in the bottle for a second time, producing gas to make the champagne sparkle. If too much sugar is added and the air pressure in the bottle is too high, the cork will be ejected. Similar processes take place inside submarine volcanoes.

  Since volcanoes are located on the ocean floor, why didn’t the sea water prevent the volcano from erupting? Countries such as Iceland also have submarine volcanoes, and in general, their magma flows slowly. There is a layer of water vapor outside the magma to isolate the high-temperature magma from the low-temperature seawater, and the magma will slowly cool down quietly in the seawater. However, if the internal pressure of the magma is very high, the eruption speed is too fast, and the high-temperature magma breaks through the water vapor and directly contacts the icy seawater, then the rapidly vaporized seawater heated by the high temperature of the magma will explode in an instant. The magma was torn apart by the explosion, and the hot interior was again exposed to icy seawater, triggering a chain explosion. This chain explosion process caused by the full contact of high-temperature objects and low-temperature objects is called “fuel-coolant interaction”. After the furnace core of a nuclear power plant reactor melts, the high-temperature core material comes into contact with the low-temperature cooling water, which will also produce a similar chain explosion.

High-temperature magma and low-temperature seawater contact, causing chain explosions
Will 2022 be the “Year Without Summer”?

  In Volume 35 of the “Full Text of Song History” compiled by an anonymous record, such a sentence is recorded: “In the fifth year of Baoyou (1258), the West Lake Binghe.” With just a few words, those who have read it can imagine Hangzhou in their minds. The unprecedented scene of the complete freezing of the West Lake was deeply shocked. What made the Hangzhou West Lake in the south of the Yangtze River completely freeze? The answer may be due to the eruption of Salamas volcano in Indonesia in 1257. The volcanic eruption caused a subsequent period of drop in global average temperature and caused the summer to disappear and the winter to be colder, known as the “year without summer”.
  In general-scale volcanic eruptions, most of the volcanic material that erupts stays in the troposphere. Air movement in the troposphere is active, and volcanic material stays for a few months at most before being brought to the surface by precipitation. However, some violently erupting volcanoes can eject volcanic material higher into the stratosphere. If volcanic material enters this atmospheric region, they can stay there for long periods of time and reflect sunlight, thereby lowering global temperatures. The most recent volcanic eruption to affect global temperatures was the 1991 eruption of Mount Pinatubo in the Philippines, which sent about 20 million tons of sulfur dioxide into the stratosphere and caused a 0.6°C drop in global average temperatures.

A portion of the volcanic ash rose to the stratosphere

  The eruption plume of Tonga’s submarine volcano spewed massive amounts of volcanic material into the stratosphere, which some speculated could lead to another year without a summer. But calculations suggest that the roughly 400,000 tonnes of sulphur dioxide injected into the stratosphere by Tonga’s submarine volcanic eruption is not enough to have any global cooling effect, but could have a cooling effect in the southern hemisphere, leading to a slightly cooler winter. People living in the southern hemisphere can see purple sunsets months after the eruption.
  But do undersea volcanoes in Tonga really have no effect on the climate? The answer to this question is not absolute.
  After the Tonga volcano erupted, scientists used satellite data to discover unusual rippling patterns in the atmosphere. None of the previous volcanic eruptions have seen similar ripples. How exactly did these ripples form?
  The ripples consist of dozens of concentric circles of varying sizes, each of which represents a fast-moving wave in the atmosphere, and the largest ripple has a radius of 16,000 kilometers! These waves extend from the sea surface all the way to the ionosphere of the atmosphere. The meteorologists explained that these waves are called atmospheric gravity waves, which are only produced when the atmosphere is disturbed vertically, not horizontally.

Atmospheric Gravity Waves

  Although the violent explosion of the Tonga volcano was short-lived, its impact on the atmosphere was long-lasting and complex. Atmospheric gravity waves can interfere with the cyclical changes in wind direction in the tropics, and the climate in many regions, including Europe, will still be affected for some time to come.
The vast majority of volcanoes are located under the sea

  About 80% of the volcanic eruptions that occur on Earth each year come from submarine volcanoes. Undersea volcanoes erupt on a regular basis, creating new geological formations that serve as habitats for deep-sea creatures. In 2009, scientists discovered the deepest underwater volcanic eruption to date, a deep-sea volcano also near Tonga called Mount Simata, which erupted 1,219 meters above sea level.

The development process of submarine volcanoes
1. The seabed cracks and the magma gushes out
2. The submarine volcano erupts, forming a crater
3. The crater keeps rising, coming to the sea and forming islands

  Some oceanographers estimate that there may be as many as 1 million volcanoes on the bottom of the Pacific Ocean alone—roughly 750 times the number of volcanoes on land. Even the largest volcano in the world is located under the sea. On the seabed of the Pacific Ocean off the east of Japan, there is the largest volcano (extinct volcano) in the world, Otamu Volcano. The total area of ​​this giant submarine volcano is 310,000 square kilometers, which is approximately equal to the combined area of ​​Shandong and Shanxi provinces.
  Seamounts are found throughout the ocean, and when magma in the mantle rises to the top of the seamounts, it erupts. Erupted and hardened lava or magma forms new seafloor material. In the area where the oceanic plates meet, there are structures called mid-ocean ridges, from which magma continuously flows to form new oceanic crust. Mid-ocean ridges are also active areas for submarine volcanoes and earthquakes. Mid-ocean ridge volcanoes spew far more lava than all other volcanoes on Earth combined.
  Hydrothermal geysers are formed when magma from underwater volcanoes mixes with cold water. Scientists first discovered these high-temperature geysers in 1979, and they nourish the life of many deep-sea creatures. Scientists have so far discovered more than 500 new species near such vents, including chemosynthetic autotrophs that synthesize organic matter without sunlight.
  If the geological structure left by the crater when the submarine volcano erupts can extend all the way and break through the sea, it will become a volcanic island. In the Hawaiian Islands, a young submarine volcano is constantly heading to the sea, and scientists predict that it will break through the sea in 50,000 years and form a new volcanic island.
  The Tonga submarine volcanic eruption caused a total of 3 deaths, more than 90,000 people were affected, and numerous buildings, roads and other construction facilities were damaged. If a volcanic eruption of a similar magnitude occurred in a populated area such as the Pacific Northwest coast, the consequences would be dire.
  Judging from the history of volcanic eruptions in Tonga, there will be a large volcanic eruption in the region every 1,000 years, and the last major eruption happened just over 1,000 years ago. Tonga’s submarine volcano is currently inactive, but is it accumulating energy for the next big eruption?
History of Volcanic Eruptions in China

  The earliest written record of volcanoes in my country comes from the “Shanhaijingju”, which records the eruption of the volcano where the Haotian Temple in Datong, Shanxi Province is located in the Northern Wei Dynasty (AD 5). “Ningguta Chronicles” records the scene of the violent eruption of the Wudalianchi volcano in the northeast: “The fire is soaring to the sky, its sound is like thunder, day and night, the sound is heard for fifty or sixty miles, and all those who fly out are black rocks and sulfur. In 1951, the volcano in the central Kunlun Mountains in Xinjiang erupted continuously for several days and nights, and finally the crater left a geological structure with a height of 145 meters on the ground.
Volcanic pumice

  After Tonga’s submarine volcano erupted, my country also launched a satellite survey. According to the remote sensing images of the “Gaofen-1B satellite” released by the Ministry of Natural Resources of my country on January 18, there are a large number of red and brown pumice strips floating in the sea area around tens of kilometers around Hongaha Apay Island. More than 10 kilometers long.
  Volcanic pumice has a large number of holes opened by air bubbles, and the volume of air bubbles accounts for more than 70% of the total volume of pumice. Under the action of surface tension, seawater will form a water film at the mouth of the hole and cannot enter the hole, so this pumice stone can float on the sea surface. Pumice stones can become natural rafts for creatures to move between islands, oceans and continents, but pumice stones can also be swallowed as food by marine fish, killing large numbers of fish.
  Pumice is also an industrial raw material. The porous structure of pumice allows it to be used as a filter, dryer and abrasive. If the pumice particles are used as the aggregate of the concrete, the formed concrete can have better thermal insulation and sound insulation effects.

Volcanic pumice
Undersea volcano creates giant bubble

  In the Aleutian Islands, west of Alaska, highly sensitive listening equipment has recorded every explosion and vibration of more than 80 active volcanoes here in recent years. In 2017, an undersea volcano in the Aleutians erupted, and during nine months of volcanic activity, listening devices recorded a low, strange melody. It’s called odd because it’s repeated over 250 times.
  Lyons, the American scientist in charge of the monitoring, was puzzled by the source of the strange melody until his colleagues discovered a log from a U.S. Navy officer. In 1908, when the Bogslov Volcano (also located in the Aleutian Islands) erupted, officers and soldiers on a warship sailing through the waters near the volcano noticed a huge semi-circular dome on the sea surface. The dome expands and contracts, and finally explodes, emitting a huge amount of smoke. Lyons wondered if the strange melodies had something to do with the giant bubbles. By modeling, he found that undersea volcanic eruptions can create giant bubbles up to 400 meters in diameter.
  Lyons explained, “All the gas and ash in the plume from the volcano stays underwater, but they have to come out.” The mysterious low-frequency melody comes from the expansion and contraction of the bubbles. Once the bubbles burst on the water’s surface, toxic gases such as hydrogen sulfide and sulfur dioxide enter the air, killing seabirds such as albatrosses and gulls that pass nearby.

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