What caused the volcanic eruption?

1. Sea level change may lead to volcanic eruption.

Hot magma runs underground and spews out at the right time, forming a volcanic eruption. What factors "pulled" the "trigger" of volcano? Recently, a geological research group of Cambridge University in England suggested that sea level change may be one of the reasons for volcanic eruption.

In the past, scientists have been trying to find the cause of volcanic eruption from earthquakes and tidal changes. The research of Cambridge University provides a new direction to explain this phenomenon, and the related results are published in the latest issue of Geophysical Research Bulletin of the United States.

The statistical records of global volcanic eruptions in the past 300 years show that the possibility of global volcanic eruptions in winter months in the northern hemisphere has increased by 18%. This phenomenon is particularly evident in the Pan-Pacific region. In recent months, the frequency of volcanic eruptions in some places is even 50% higher than the average.

The geological research team of Cambridge University believes that the snowfall here in winter is much higher than that in the southern hemisphere, because the land area in the northern hemisphere is larger than that in the southern hemisphere. A large amount of snowfall makes the global sea level drop by about 1 cm in winter in the northern hemisphere, and the pressure of sea level change on coastline and islands may be the cause of volcanic eruption.

This finding of Cambridge University is consistent with a research observation of new york University in the United States. This observation record shows that in the past 85,000 years, the frequency of volcanic eruptions was high during the period of frequent sea level changes.

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The research shows that during the period of intense geocentric activity and great changes in the surface, a large number of magma formed columnar eruption, which made high-temperature substances from the mantle diffuse and flow on the surface. It is speculated that magma covers an area with a radius of about 500 kilometers. Such an explosion lasted for one or two million years, forming millions of cubic kilometers of lava.

3. Volcanic eruption caused by rainstorm

John Murray, a British volcanologist, recently discovered that a volcanic eruption may be caused by heavy rain. Therefore, as long as we observe the weather forecast in the future, we can know in advance whether this volcanic eruption will happen, so as to make preparations in advance and avoid casualties.

Volcanic eruption caused by rainstorm is a kind of eruption called "dome collapse", which is the most dangerous form of volcanic eruption. More than 70% of volcano-related deaths in the 20th century were caused by this type of volcanic eruption. Murray said that volcanic eruptions caused by heavy rains are often large-scale eruptions. For example,1On May 8, 980, the San hellens volcano erupted, sending 520 million tons of volcanic ash into the air 25 kilometers high, and the ejected rocks and debris fell 30 kilometers away from the volcano.

Volcanic eruptions often have signs months ago, because before the sudden eruption, magma will squeeze outward from below, forming a visible dome on one side of the volcano. The eruption of small volcanic rocks will increase the uplift of the dome and make it more unstable until it finally collapses, resulting in huge explosion release pressure. But when it will suddenly break out, it is difficult to accurately predict.

The researchers studied the relationship between the last three eruptions of Montserrat Montsoufriere volcano in Latin America and the climate. After an eruption about 300 years ago, this volcano became very active on1July, 995 18. Before these three outbreaks, heavy rain made the dome that was about to collapse more unstable. Adrian Matthews, a British scholar, said that the eruption of this volcano on July 29th, 20001year attracted special attention, because when tropical storm Bali hit the Caribbean island, the dome collapsed in a few minutes and then suddenly erupted. This tropical storm was the first in July that year.

Matthews pointed out that heavy rain may also play a role in triggering other volcanic eruptions. He believes that one of the reasons why rainstorm can cause volcanic eruption is that rainstorm washes away the rocks on the dome foundation and makes it unstable; But it is more likely that a large amount of rainwater seeps into the cracks in the dome and is heated and evaporated by high-temperature lava, which greatly increases the pressure when the rainwater turns into steam, thus triggering volcanic eruption.

The researchers said that although the rainstorm is not necessarily the "fuse" of volcanic eruption in every case, in the absence of rainfall, the dome may eventually collapse because the rainstorm only exerts additional effects. The introduction of rainstorm as a coefficient in the volcanic eruption prediction program will undoubtedly increase the accuracy of volcanic eruption prediction. It is an important step to accurately predict the collapse of various domes.

The sudden eruption of the volcano is particularly deadly, because it will wash the hot toxic gas, hot volcanic ash and lava "river" formed by rubble to the foot of the mountain at a speed of 80 kilometers per hour, which is much more harmful than volcanic ash. A large number of rubble is suspended by the heat generated under the dome, just like a raging mountain torrent rushing down the mountain, destroying all obstacles along the way. Their influence is extremely great, people may avoid volcanic ash, but almost no one can survive the impact of pyroclastic flow.