1, frequent earthquakes
Before a volcano erupts, there are often microseisms, the volcanic crust breaks and the volcanic vibration increases, indicating that the volcano is close to eruption. Seismographs can detect it, so there are seismic stations around active volcanoes abroad. For example, there are 13 around Mount St. hellens, 47 around Mount Kilauea and 6 around Mount Merapi. For example, before the eruption of San hellens volcano in May 1980, there were as many as 30 earthquakes of magnitude 3 per day, and before the eruption of Soufriere volcano in April/978, the number of sensible earthquakes reached 15 per hour.
The process of volcanic activity often leads to many small earthquakes, and big explosions can lead to strong earthquakes. Earthquakes often lead to volcanic activity. Of the 27 volcanic activities recorded by 1999, 14 occurred within more than two months after the earthquake in Turkey. Rock fracture caused by material movement inside the earth is the fundamental cause of volcanoes and earthquakes. Astronomical factors such as the tidal force of the sun and the moon also play a legitimate role in the earthquake, but the fundamental driving force is still the accumulation of energy inside the earth.
Volcanic eruption and earthquake are twin brothers. 1August, 1999 to 10/October, major earthquakes occurred frequently, and volcanic activity also surged. There are 17 volcanic eruptions in the world.
2. Geological and topographic changes
Before the volcanic eruption, the underground magma activity was intense, which produced in-situ stress, changed the geological terrain, and led to ground cracks, collapse and displacement. There were signs of volcanic eruption months ago, because before the sudden eruption, the magma would 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.
For example, before the eruption of Katmai volcano in Alaska in 19 12, many ground fissures or collapses suddenly appeared around it, or gas and dust were emitted. 1978 Before the eruption of Kabbah volcano in Ardu in Djibouti's Afar Triangle, a protrusion as high as 100 meters suddenly appeared. 1979 Before the eruption of San hellens volcano, a dome appeared on its northern slope. By 1980, the height of the dome increased rapidly, with the fastest increase of 45 cm per day. Finally, on May 18 of that year, it broke through this dome and broke out. However, before the eruption of Crafra volcano in Iceland in 1980+00, the ground subsidence occurred, which was also related to magma migration.
3. Abnormal odor
Before the volcanic eruption, magma had accumulated in the ground and approached the surface. At this time, some gas and water vapor in the magma floated out first. Among these smells, there are sulfur vapor and many sulfur-containing gases. Therefore, people can usually smell unpleasant smells.
So foreign countries often take gas samples near volcanoes for analysis. If the abnormal gas increases, it means that some volcanic gas has been "advanced" before the volcanic eruption.
4. Ground temperature, air temperature and water temperature rise.
Before the volcanic eruption, due to magmatic activity, the nearby ground temperature, air temperature and water temperature rose and the ice and snow melted. The temperature of groundwater will be higher than usual, or abnormal. Many tall volcanoes are above the snow line all the year round. If the ice and snow on the volcano melt, it indicates that it will erupt. Such as San hellens, Couto Paxi, Ruiz and other volcanoes have this phenomenon, and snowmelt water even causes mudslides or flash floods.
5. Animal abnormality
Similar to the situation before the earthquake, some animals will be agitated, escape, out of control, attack people, collective migration, death and other abnormal phenomena. Birds are in a panic. They may bump into trees without knowing their direction, and then die.
Especially near the volcanic eruption, more gas and water vapor are emitted. Because these gases are toxic, and the temperature of magma is very high, they gather underground, where the temperature of topsoil rises, which will make those sensitive animals unable to adapt and run away. Some animals with weak resistance will be poisoned and die.
Zoologists in many countries believe that animal anomalies are indeed a harbinger of some disasters. Volcanic eruption or earthquake is a huge energy release. Before volcanic eruption, geomagnetism, geoelectricity, ground temperature, groundwater, atmosphere, etc. All kinds of changes will happen. Some animals behave abnormally because they feel very sensitive.
6. Abnormal water quality
Volcanic eruption is the accumulation and eruption of crustal energy, which is closely related to groundwater. First, it has a direct impact on water quality, fish and marine animals. Underground fish prophet. For example, deep-sea fish swim to shallow water and find a group of strange fish or special invisible fish or other deep-sea animals in a certain area. Animals living on the ground and underwater suddenly appear or die. And the change of ocean salinity, the abnormal swimming direction of fish and so on.
7. Electromagnetic anomalies
Volcanic eruptions, like earthquakes, will produce strong geomagnetic changes and electromagnetic radiation, leading to changes in the magnetic field structure inside the earth. Many scientific observation data also fully show the electrical characteristics of volcanic eruption, and abnormal changes of geomagnetism and geoelectricity are observed before and after volcanic eruption. For example, a few years before the eruption of Izu Oshima volcano, the geomagnetic field began to change abnormally, and during the eruption, the total magnetic field intensity changed dramatically (because all magnetic fields are caused by changing electric fields, the change of magnetic fields means the change of electric fields). On the measuring route through the central crater, repeated resistivity measurements by direct current method found that anomalies began to appear about one year before volcanic eruption; The anomaly reached its maximum three months before the volcanic eruption.
8.volcanic ash
1985, when Mount Ruiz erupted, the gray level of the volcano sprayed into the air reached 8000 meters. The sign of disaster was that volcanic ash rained down on the streets of Almero. As night falls, the rapid debris flow rushes down from the volcano, and the mountains and rivers flood rapidly.
9, instrument determination
Although human sensory organs are not as sensitive as some animals. However, we can observe with precision instruments. Therefore, foreign experts (excluding China experts) put special thermometers underground to measure the changes of land temperature; Air samples are often used to test and analyze their composition; An instrument that can sensitively detect gravity changes is also used to collect information on whether magma accumulates in large quantities underground. If there is more magma underground, the gravity there will increase. The noise often made underground before volcanic eruption can also be detected by scientific instruments.
10, acoustic wave change
At this time, New Zealand scientists have recently discovered a new method to predict volcanic disasters.
In September, 200012000, some scientists in New Zealand announced that they had discovered a new method to predict volcanic disasters, that is, to analyze the direction of the formation of cracks in the earth's crust by using sound waves occurring in the center of the earth's interior, and to predict the exact time of volcanic eruption at one time.
These New Zealand scientists collected a large number of scientific data of two recent large-scale eruptions in Mount Ruapehu, New Zealand, and found that the sound waves in the center of the earth showed regular changes before and after the volcanic eruption. These sound waves are formed by the fracture of rock layers under the surface. Before a volcano erupts, cracks usually appear in the crust. In this way, as long as people closely observe the direction of those cracks, they can predict the exact time of volcanic disasters in advance. However, scientists also pointed out that this new method of predicting volcanic disasters can only be used as part of various prediction techniques until more relevant information is collected.
1 1, rumbling
Due to the expansion of magma and gas, the noise it made before it rushed out of the crater indicates that the eruption is coming.
12, other signs
(1) Blackening of silverware-Sulfur and silver can combine to form black silver sulfide, so the surface of silverware will be blackened before volcanic eruption.
(2) Gas comes out of the crater or the gas comes out faster than before.
(3) The volcanic crust breaks and the volcanic vibration phenomenon increases.
(4) Small animals (such as pigs, dogs, cats, poultry, etc. ) will be irritable.
(5) Birds panic. They may hit a tree and die. Animals get out of control and attack humans.
(6) If people suddenly feel restless, restless, and the sexual desire of men and women suddenly increases, it is also a sign of disaster.
(7) The water in the well is bubbling or smells in the water.
(8) There will be ground light or colorful clouds.
(9) A pungent smell, usually sulfur and hydrogen sulfide, can be smelled in the crater and surrounding areas.
Abnormal changes of electromagnetic waves around (10).
How to escape after volcanic eruption
1, to deal with the hazards of lava. Among the hazards caused by volcanoes, lava flows may pose less threat to life, because people may run out of the route of lava flows.
2, to deal with the harm of spray. If you escape from the vicinity of a volcanic eruption, the hard helmet, motorcyclist's helmet or rider's helmet used by construction workers will give you some protection. In a wider area, it may not be possible to escape.
3. Respond to the hazards of volcanic ash. Wearing goggles, a breathing mask or ski goggles can protect your eyes-but sunglasses can't. Cover your mouth and nose with a damp cloth, or use an industrial gas mask if possible. After arriving at the shelter, take off your clothes, thoroughly wash the exposed skin and rinse your eyes with clear water.
4. Respond to the hazards of gas pellets. If there is no solid underground building nearby, the only chance of survival may be to jump into the water; Hold your breath for about half a minute, and the ball will roll over.
Remember: Volcanoes tend to increase in activity before eruption, accompanied by rumbling and steam gas overflowing, and sulfur can be smelled from local rivers. Annoying acid rain, loud rumbling or plumes of green steam from volcanoes are all warning signs. When driving away, remember that volcanic ash will make the road slippery. Don't take the canyon route, it may become the road that Rajal passes through.