What are the causes of earthquakes and volcanoes?

Earthquakes and volcanoes have existed since ancient times, and their eruption can produce great destructive power, killing thousands of people in just a few minutes, so people have a strong sense of fear. In history, the most violent volcanic eruption we know happened around 1500 BC, which destroyed the island of Sala in the northern part of Crete in the Aegean Sea. At that time, people living on the island didn't realize the potential signs of volcanic eruption, but at this time, the pressure in the depths of the earth was getting bigger and bigger. When the pressure reached enough, it eventually led to volcanic eruption. Although an emergency may add a lot of color to the legend of Atlanta, Sarah Island was once destroyed, and Crete Island was seriously damaged by the deposition of volcanic ash. Even the originally prosperous civilization was not spared and gradually declined. In fact, this volcanic eruption plunged the whole eastern Mediterranean into chaos, and even the Egyptian empire suffered a fatal blow and entered a permanent decline.

There is a volcano near Naples, Italy. It was so silent for a long time that people gradually forgot its danger. But in 79 AD, it suddenly broke out and buried the cities of Pompeii and Hershem. Pliny, a great Roman writer, was killed because he was close to the volcano and tried to observe and describe the spectacular scene of volcanic eruption. The volcanic eruption killed 4000 people. Mount Etna in Sicily is the highest and most active volcano in Europe. It broke out in 1669, resulting in 20,000 deaths. Iceland volcano erupted on a large scale in 1783, Tamboura volcano on Sambuwa Island in Indonesia erupted in 18 15, and another volcano named Crakado in Indonesia also had the same tragedy in 1883. These three volcanic eruptions have caused countless deaths and heavy casualties. 1902, the Perry volcano erupted in Martinik Island, West India, and hot toxic gas poured down, filling the city of St. Bill, the former capital of Martinik Island next to the volcano. Within three minutes, all 38,000 people in the city were killed, except those who were waiting to be executed in the underground prison.

The disaster brought by the earthquake is far more than that. It can kill more people. On June 24th, 1556, a strong earthquake occurred in Shanxi Province, China. It is estimated that about 800,000 people died in just a few minutes. 1703 The Tokyo earthquake claimed about 200,000 lives. 1737, Calcutta earthquake, 300,000 people were killed. The worst earthquake in modern European history occurred in 1 755165438+10/0/. The earthquake destroyed Lisbon, Portugal, followed by a tsunami and volcanic eruption. 600,000 people were killed in the earthquake. 18 12 There was a terrible earthquake near the Mississippi River, which is today's New Maidi Town. After the earthquake, almost no one survived.

So, what caused these phenomena? First of all, we must rule out the statement of God's revenge and God's anger. Aristotle believes that part of the air exists in the complex and changeable underground space, and it is released under some special conditions to form an earthquake. But people have gradually begun to understand volcanoes and earthquakes, and they have noticed that most of them occur in some specific areas. Nearly 300 of the 500 volcanic activities on the earth occurred on the boundary curve of the Pacific plate, about 8 times occurred on the Maya chain, and there was a small amount of volcanic activity along the Mediterranean coast. At the same time, people have noticed that these areas are also earthquake-prone areas. It can be seen that volcanoes and earthquakes are interrelated to some extent and have the same root.

The Lisbon earthquake has promoted the in-depth study of such problems in the scientific field. As we mentioned earlier, people have installed seismographs everywhere. 1906 A major earthquake caused serious damage to San Francisco. After investigating the earthquake site, American seismologist Harry Freding Reid noticed that some areas near the city were displaced. The "cracks" in the ground show that one side seems to be staggered forward relative to the other. Most people think that this "crack" was formed only when the earthquake happened, but Rhett has a different view. He believes that "cracks" (or "faults") should have existed before the earthquake (we now call them "San Andes faults"). With the passage of time, the underground pressure gradually increases, which makes the two sides of the fault move in opposite directions. Under normal circumstances, both sides of the fault are relatively static due to friction. But with the increase of pressure, one side of the fault moved and the other side was forced to shake constantly, which was enough to destroy a city and kill thousands of creatures.

Although Reid's theory is correct in the general direction, it is not until people understand the structure of the plate that the causes of earthquakes are thoroughly understood. It has been understood that the formation of great power on the earth is due to the very slow movement of plates on the earth, but the energy at the edge of plates sometimes leads to other movements, forming a phenomenon similar to that observed by Reid during the San Francisco earthquake. In the final analysis, the San Andean fault is actually a fault formed between the bottom of the North American plate and the bottom of the Pacific plate.

The fault zone around the world is a very unstable zone. Once hot magma seeps out of the ground, it will lead to volcanic eruption. When two plates collide with each other, the edges of the collision are wrinkled, forming mountains. Today, the highest mountain range in the world, the Himalayas, was formed because the Indian plate collided with the Asian plate in the drift movement. Sometimes one plate can slide into the bottom of another plate and be sucked into the seabed to form a trench. In some places, the depth can reach 1 1 km.

It is not until people discover the plate structure of the earth that they can fully understand the complicated and changeable crustal phenomena. This discovery makes the seemingly impossible things clear at once, and similar discoveries often represent the formation of a brand-new theory.