shake? How are earthquakes formed? What are the warning signs before an earthquake strikes? What if the earthquake comes? Today, let us solve these 4 problems! I hope that the students can learn more about geography and reserve common sense for survival!
(1) Why do earthquakes
The vast majority of earthquakes are caused by the movement of the earth's crust. Hard rocks are subjected to force during the movement of the earth's crust, deforming or even breaking, often causing earthquakes.
Although there is still debate about where the driving force of the crustal movement comes from, and there are many speculations about the root cause of the earthquake, there is no doubt about the assertion that the "earthquake is directly caused by the rupture of the rock there". of.
The vast majority of earthquakes occur because of new fractures in the underground rock, or the dislocation of the original cracks again. Strong earthquakes mostly occur in the places where the original fractures occurred underground. When the underground rock is close to rupture, the gravitational pull of the sun and the moon, changes in the pressure of the atmosphere or water (reservoirs) on the ground can all contribute to the rupture, which can trigger earthquakes.
Earthquakes are often accompanied by volcanic eruptions. A large amount of hot magma is ejected from the depths of the stratum, and its volume expands rapidly and impacts the crust, thus often causing earthquakes.
(2) How earthquakes are formed
1, tectonic earthquakes: earthquakes caused by the dislocation and rupture of rock formations deep underground are called tectonic earthquakes. Such earthquakes are the most frequent and the most destructive, accounting for more than 90% of earthquakes in the world.
2, volcanic earthquake : Earthquakes caused by volcanic action, such as magma activity, gas explosions, etc., are called volcanic earthquakes. Volcanic earthquakes are only possible in volcanically active areas, and such earthquakes account for only about 7% of the world's earthquakes.
3, collapse earthquake : Earthquakes caused by the collapse of the top of an underground cave or mine are called collapse earthquakes.Such earthquakes are relatively small in scale and infrequent, and even if they occur, they often occur in limestone areas with dense karst caves or large-scale underground mining areas.
4. Induced earthquake: The earthquake caused by reservoir water storage, oil field water injection and other activities is called induced earthquake. Such earthquakes only occur in certain specific reservoir areas or oil field areas.
5. Artificial earthquake: The ground vibration caused by man-made underground nuclear explosion, explosive blasting, etc. is called artificial earthquake. Artificial earthquakes are earthquakes caused by human activity. For example, the vibration caused by industrial blasting and underground nuclear explosion; high-pressure water injection in deep wells and water storage in large reservoirs increase the pressure of the earth's crust and sometimes induce earthquakes.
(3) Signs before the earthquake
1. Animal anomalies: snakes, fish, birds, mice and other animals are called "live instruments" for earthquakes. The abnormal reaction of mice came first. The big mice ran around in groups with the little mice in their mouths, and the weasels moved. Large and small livestock such as dogs bark and bark, go up to the wall, pigs do not eat, sheep do not enter the pen, and cats scratch and scratch. Horses and cows do not eat food or run around or stay in a daze. The abnormal reactions of chickens, ducks, geese and other animals are often closely related to earthquake activity. Before the earthquake, the fish floated in groups, some were in a daze, some turned white, some feigned death, some stood upside down and swirled in the water, or jumped out of the water.
2. Plant omen: The response of some plants to earthquakes is representative, and the response of mimosa is more typical. The leaves of the mimosa are open during the day and gradually close automatically at night. However, scientists found that on the eve of the earthquake, the mimosa looked a little abnormal: its leaves were closed during the day, and the leaves were half-open at night. When the earthquake happened, the leaves of the mimosa all opened.
3. Terrain changes: Before the terrain changes, there will be terrain changes, such as vertical lift, horizontal displacement, and ground inclination.
(4) What to do when the earthquake comes
1, the earthquake is fierce, and it often causes great lethality in an instant. When an earthquake occurs, panic is the first reason for most people to be killed. Keep calm, adopt the principle of "fall down, cover, and hold hands", narrow down the target as soon as possible and keep your body under a solid barrier.
2. The shock absorber does not distinguish between the main shock and the aftershock. It must not be taken lightly.
3, "Remember the principle of "don't be in a hurry during a major earthquake, find hiding places first, stay away from dangerous areas, and save your physical strength when buried".
