Tsunami
A tsunami is a powerful and destructive wave. The waves caused by this wave movement are turbulent and turbulent, and the waves they roll up can reach tens of meters in height. This "water wall" contains a huge amount of energy and is invincible after rushing onto land, often causing serious damage to life and property. The waves formed by the Chilean tsunami moved tens of thousands of kilometers without losing strength, which shows its huge power.
A tsunami is a catastrophic wave, usually caused by an undersea earthquake with a source within 50 kilometers under the sea and a magnitude of 6.5 or above on the Richter scale. Tsunamis can also be caused by underwater or coastal landslides or volcanic eruptions. After a shock, shock waves spread over great distances in ever-expanding circles on the sea surface, just like the waves produced by a pebble dropped into a shallow pool. The wavelength of a tsunami is greater than the maximum depth of the ocean, and its orbital motion is not greatly hindered near the seafloor. The wave can propagate regardless of the depth of the ocean.
Shortly after the violent shaking, huge waves roared, crossing the coastline and fields with overwhelming force, rapidly attacking the cities and villages on the shore. In an instant, people disappeared in the huge waves. All the facilities and collapsed buildings in the port were swept away by the violent waves. Afterwards, the beach was in a mess, with broken wood and human and animal corpses everywhere. Earthquakes and tsunamis bring huge disasters to mankind. At present, humans can only prevent or reduce the losses caused by sudden disasters such as earthquakes, volcanoes, and tsunamis through prediction and observation, but they cannot yet control their occurrence.
A tsunami is a powerfully destructive wave. The waves caused by this wave movement are turbulent and turbulent, and the waves they roll up can reach tens of meters in height. This "water wall" contains a huge amount of energy and is invincible after rushing onto land, often causing serious damage to life and property. The waves formed by the Chilean tsunami traveled tens of thousands of kilometers without losing strength, which shows its huge power.
A tsunami is a powerful and destructive wave. A tsunami is a catastrophic wave, usually caused by an undersea earthquake with a source within 50 kilometers under the sea and a magnitude of 6.5 or above on the Richter scale. The waves caused by this wave movement are turbulent and turbulent. The waves it stirs up can reach tens of meters in height. This "water wall" contains a huge amount of energy and is invincible after rushing onto land, often seriously destroying lives and causing property damage. The waves formed by the Chilean tsunami moved tens of thousands of kilometers without losing strength, which shows its huge power.
They are very different from the waves or tides generated by the wind. The breeze blows across the ocean, creating relatively short waves. The resulting water flow is limited to shallow water bodies. Strong winds can roll up waves with a height of more than 3 meters in the vast ocean, but they cannot shake the water in the depths. Tides sweep across the world twice a day. The currents it generates can penetrate deep into the bottom of the ocean like tsunamis, but tsunamis are not caused by the gravity of the moon or the sun. They are generated by underwater earthquakes, or by volcanic eruptions, meteorite impacts, or underwater landslides. Tsunami waves can reach speeds of more than 700 kilometers per hour in the deep ocean and can easily keep pace with a Boeing 747 aircraft. Although it is fast. But tsunamis are not dangerous in deep water. A single wave of less than a few meters can be more than 750 kilometers long in the open ocean. The tilt of the sea surface produced by this effect is so subtle that such waves usually occur inadvertently in deep water. It's over. Tsunamis move silently and imperceptibly through the ocean, but if unexpectedly in shallow water they can reach catastrophic heights.
Howling is a powerful and destructive wave. Tsunamis can be caused by underwater earthquakes, volcanic eruptions, or geodetic activity such as underwater collapses and landslides.
When an earthquake occurs, the seafloor strata fracture and some strata rise or sink suddenly, causing the entire water layer from the seafloor to the sea surface to "tremble" violently. This "shaking" is very different from the waves you usually see. Waves generally only rise and fall near the sea surface, and the depth involved is not large. The amplitude of the waves attenuates quickly with the water depth. The "jitter" of seawater caused by earthquakes is the fluctuation of the entire water body from the bottom of the sea to the sea surface, and the energy contained in it is amazing.
The rough waves set off by tsunamis can reach a height ranging from more than 10 meters to dozens of meters, forming a "water wall". In addition, tsunamis have large wavelengths and can travel thousands of kilometers with very little energy loss.
Due to the above reasons, if a tsunami reaches the shore, the "water wall" will rush onto the land, posing a serious threat to human life and property.
Tornado
A tornado is the product of a thunderstorm in the clouds. Specifically, a tornado is a form in which a small part of the huge energy of a thunderstorm is concentrated and released in a small area. The formation of a tornado can be divided into four stages:
(1) The instability of the atmosphere produces a strong updraft, which is further strengthened due to the influence of the maximum passing airflow in the jet stream.
(2) Due to the interaction with the wind that has shear in both speed and direction in the vertical direction, the updraft begins to rotate in the middle of the troposphere, forming a mesoscale cyclone.
(3) As the mesoscale cyclone develops toward the surface and extends upward, it itself becomes thinner and intensifies. At the same time, a small area of ??enhanced coordination, that is, a nascent tornado is formed inside the cyclone. The same process that creates a cyclone forms the core of the tornado.
(4) The rotation in the core of a tornado is different from that in a cyclone. It is strong enough to make the tornado stretch all the way to the ground. When the developed vortex reaches the height of the ground, the surface air pressure drops sharply and the surface wind speed rises sharply, forming a tornado.
Lightning
The atmospheric electric field during a thunderstorm is significantly different from that on a sunny day. The reason for this difference is that the electric charge accumulates in the thundercloud and forms the polarity of the thundercloud. , the resulting lightning causes huge changes in the atmospheric electric field. But where does the electricity in thunderclouds come from? That is to say, what physical processes in thunderclouds lead to its electrification? Why can thunderclouds accumulate so much charge and form a regular distribution? This section will answer the question these questions. We have already mentioned before that the macroscopic process of thundercloud formation and the microphysical processes occurring in thunderclouds are closely related to the electrification of clouds. Scientists have conducted a large number of observations and experiments on the electrification mechanism of thunderclouds and the regular distribution of charges, accumulated a lot of data and proposed various explanations. Some arguments are still controversial today. To sum up, the main electrification mechanisms of clouds are as follows:
A. "Ion flow" hypothesis in the initial stage of convective clouds
There are always a large number of positive ions in the atmosphere And negative ions, on the water droplets in the cloud, the charge distribution is uneven: the outermost molecules are negatively charged, the inner layer is positively charged, and the potential difference between the inner layer and the outer layer is about 0.25 volts higher. In order to balance this potential difference, water droplets must "preferentially" absorb negative ions in the atmosphere, so that the water droplets gradually become negatively charged. When convection develops, lighter positive ions are gradually carried to the upper part of the cloud by the updraft; and Because the negatively charged cloud droplets are relatively heavy, they remain in the lower part, causing the separation of positive and negative charges.
B. Charge accumulation in cold clouds
When convection develops to a certain stage, When the cloud body reaches a height above the 0°C layer, there are supercooled water droplets, graupel particles, and ice crystals in the cloud. This type of cloud is composed of water vapor condensates of different phases and has a temperature lower than 0°C, and is called a cold cloud. The charge formation and accumulation processes of cold clouds are as follows:
a. The friction and collision of ice crystals and graupel particles generate electricity
Graupel particles are composed of frozen water droplets, which are white or milky white. The structure is relatively brittle. Because supercooled water droplets often collide with it and release latent heat, its temperature is generally higher than that of ice crystals. Ice crystals contain a certain amount of free ions (OH- or OH+), and the number of ions varies. It increases as the temperature increases. Due to the temperature difference between the graupel particles and the ice crystal, there must be more free ions at the high temperature end than at the low temperature end, so when the ions migrate from the high temperature end to the low temperature end, the lighter positively charged hydrogen must move. The ions are faster, while the negatively charged heavier hydroxide ions (OH-) are slower. Therefore, an excess of H+ ions occurs at the cold end within a certain period of time, causing the high temperature end to be negative and the low temperature end to be negative. Positive electric polarization. When ice crystals come into contact with graupel particles and then separate, the higher temperature graupel particles become negatively charged, while the lighter ice crystals become positively charged under the influence of gravity and updrafts. The electrically charged ice crystals are concentrated in the upper part of the cloud, while the heavier negatively charged cloud particles stay in the lower part of the cloud, thus causing the upper part of the cold cloud to be positively charged and the lower part to be negatively charged.
b. Supercooling. Water droplets freeze and electrify on graupel grains
There are many water droplets in clouds that do not freeze when the temperature is below 0°C. Such water droplets are called supercooled water droplets. Supercooled water droplets are unstable as long as they are. If shaken slightly, it will freeze into ice particles immediately.
When supercooled water droplets collide with graupel particles, they freeze immediately, which is called impact freezing. When impact freezing occurs, the outside of the supercooled water droplet immediately freezes into an ice shell, but the inside of the droplet remains temporarily liquid, and because the latent heat released by the external freezing is transferred to the inside, the temperature of the liquid supercooled water inside is higher than that of the ice shell outside. high. The difference in temperature causes the frozen supercooled water droplets to become positively charged on the outside and negatively charged on the inside. When freezing occurs inside, the cloud droplets expand and split, and the outer skin breaks into many positively charged small ice fragments, which fly to the upper part of the cloud with the airflow. The negatively charged core of the frozen droplets is attached to the heavier graupel particles. The graupel particles are negatively charged and stay in the middle and lower parts of the cloud.
c. Water droplets are electrified because they contain thin salt content
In addition to the two electrification mechanisms of cold clouds mentioned above, some people have also proposed that water droplets in the atmosphere contain thin salt content. The electrification mechanism produced. When cloud droplets freeze, the ice's crystal lattice accommodates negative chloride ions (Cl-) but excludes positive sodium ions (Na+). Therefore, the frozen part of the water droplet is negatively charged, while the unfrozen outer surface is positively charged (when the water droplet freezes, it proceeds from the inside out). As the graupel grains formed by frozen water droplets fall, they throw away the water on the surface that has not had time to freeze, forming many positively charged small cloud droplets, while the frozen core part is negatively charged. Due to the sorting effect of gravity and airflow, the positively charged droplets are carried to the upper part of the cloud, while the negatively charged graupel particles stay in the middle and lower parts of the cloud.
d． Charge accumulation in warm clouds
The above describes some of the main mechanisms of electrification in cold clouds. In the tropics, there are some clouds whose entire cloud body is located above 0°C and therefore contains only water droplets but no solid water particles. Such clouds are called warm clouds or "water clouds." Warm clouds can also cause thunder and lightning. In thunderstorm clouds in mid-latitudes, the part of the cloud body below the 0°C isotherm is the warm zone of the cloud. Electrification processes also occur in the warm regions of clouds.
In the development process of thunderclouds, the various mechanisms mentioned above may work respectively at different stages of development. However, the most important electrification mechanism is caused by the freezing of water droplets. A large number of observational facts show that clouds develop into thunderclouds only when the cloud top exhibits a fibrous strand structure. Aircraft observations also found that there are a large number of cloud particles mainly composed of ice, snow crystals and graupel particles in thunderclouds, and the accumulation of a large amount of charge, that is, the rapid electrification mechanism of thunderclouds, must rely on collision, freezing and friction during the growth of graupel particles. Wait for it to happen.
Earthquake
An earthquake is a vibration of the earth. It originates from a certain point underground, which is called the focus. Vibrations emanate from the source and propagate through the Earth. The point on the ground closest to the earthquake source is called the epicenter, and it is the earliest point to receive vibrations. Earth vibration is the most intuitive and common manifestation of earthquakes. Strong earthquakes that occur under the sea or in coastal areas can cause huge waves, called tsunamis. Earthquakes are extremely frequent, with about 5 million earthquakes occurring around the world every year.
The structure of the ball is like an egg, which can be divided into three layers. The central layer is the "yolk" - the core; the middle layer is the "egg white" - the mantle; the outer layer is the "eggshell" - the crust. Earthquakes generally occur in the earth's crust. The earth is constantly rotating and revolving, and at the same time, the interior of the earth's crust is constantly changing. The resulting force causes the crustal rock layers to deform, fracture, and move, causing earthquakes. The place where an earthquake occurs underground is called the source. The point vertically upward from the earthquake source to the surface is called the epicenter. The distance from the epicenter to the source of the earthquake is called the focal depth. Earthquakes with a focal concentration less than 70 kilometers are shallow earthquakes, earthquakes between 70 and 300 kilometers are intermediate earthquakes, and earthquakes more than 300 kilometers are deep earthquakes. The earthquake with the deepest focal depth was a magnitude 5.8 earthquake that occurred in the northern seas of Irian Jaya Province, Indonesia in 1963, with a focal depth of 786 kilometers. For earthquakes of the same size, due to different focal depths, the degree of damage to the ground is also different. The shallower the earthquake source, the greater the damage, but the smaller the spread, and vice versa.
The distance between a certain place and the epicenter is called the epicentral distance. Earthquakes with an epicenter distance less than 100 kilometers are called local earthquakes, earthquakes between 100 and 1,000 kilometers are called near earthquakes, and earthquakes greater than 1,000 kilometers are called telequakes. The farther away the epicenter is, the greater the impact and damage. Small.
The ground vibration caused by earthquakes is a complex movement, which is the result of the simultaneous action of longitudinal waves and transverse waves. In the epicenter, longitudinal waves cause the ground to move up and down. Transverse waves cause the ground to shake horizontally.
Since longitudinal waves propagate faster and attenuate faster, transverse waves propagate slower and attenuate slower, so in places far away from the epicenter, you often cannot feel up and down beating, but you can feel horizontal shaking.