First, avalanches
1. On the slopes of the snow, when the cohesion inside the snow cannot resist the gravitational pull it is subjected to, it slides down, causing a large amount of snow to collapse.
2. Avalanche is a process of snow migration on the surface of snow and mountains, and avalanches depend largely on human activities in addition to hillside morphology.
3. The main types of avalanches
Avalanches are divided into wet avalanches (also known as block avalanches) and dry avalanches (also known as powder avalanches).
A. Wet avalanches generally occur a few days after a precipitation, because the surface snow layer melts and seeps into the lower layer of snow and re-freezes, forming a "wet snow layer".
b. Dry avalanche entrains a lot of air, so it acts like a fluid.
4. Avalanches have the characteristics of suddenness, fast movement speed and large destructive force.
Expansion: Even more frightening than the avalanche itself is the air wave in front of the avalanche. Because the avalanche moves downwards from a high place with a large potential energy, such as falling or slipping down from a height of 6000 meters, it will cause violent oscillations in the air, so there is a very fast speed and even a layer of air waves, which are somewhat similar to the shock waves generated by the atomic bomb explosion
Second, sea ice
1. Refers to saltwater ice directly frozen by seawater, including continental glaciers, river ice and lake ice entering the ocean.
2. The huge ice cubes and icebergs floating on the ocean are divided into fixed ice and ice floes according to the state of motion, and the movement generated by the action of wind and ocean currents, and their thrust is related to the size and flow rate of the ice cubes.
3. Sea ice is divided into: primary ice, Nile ice, cake ice, initial ice, one-year ice and multi-year ice according to the formation and development stages.
4. Sea ice has significant seasonal and interannual changes, which have an important impact on the vertical distribution of marine hydrological elements, seawater movement, ocean thermal status and the formation of ocean bottom water; it also poses a certain threat to shipping and port construction.
Expansion: Antarctica is the world's largest natural ice reservoir, where more than 90% of the world's total ice and snow is stored. The icebergs near Antarctica are formed by the glaciers around the Antarctic continent breaking into the sea. Icebergs that appear in the waters of the southern hemisphere are often hundreds of kilometers long and wide and hundreds of meters high, like an Iceland.
Third, the tsunami
1. It is a wave with strong destructive power. When an earthquake occurs on the seabed, the seawater fluctuates violently due to the power of the seismic wave, forming a powerful wave, pushing forward, and submerging the coastal zone one by one, which is called a tsunami.
2. Underwater earthquakes, volcanic eruptions or underwater landslides and landslides can all cause tsunamis.
When the earthquake occurs, the seafloor formation breaks, and some of the formations rise or sink suddenly, resulting in a violent "shaking" of the entire water layer from the seabed to the sea surface, which contains amazing energy.
3. Tsunamis can be divided into four types.
That is, storm surges caused by meteorological changes, volcanic tsunamis caused by volcanic eruptions, landslide tsunamis caused by submarine landslides, and seismic tsunamis caused by submarine earthquakes.
Earthquake tsunami is a sharp rise and fall in the seabed terrain caused by a sharp rise and fall of the seabed when an earthquake occurs on the seabed. Its mechanisms take two forms: "descending" tsunamis and "uplifting" tsunamis. This uplift-type tsunami wave formed by the movement of the seafloor crust first manifests itself as an abnormal tidal rise on the coast.
4. Tides, which produce currents that can penetrate deep into the bottom of the ocean like tsunamis, but tsunamis are not caused by the gravitational pull of the moon or the sun, it is generated by underwater earthquakes, or by volcanic eruptions, meteorite impacts, and underwater slides.
red tide
1. Red tide, known as the "red ghost", red tide, also known as red tide, is an abnormal phenomenon in the marine ecosystem. It is composed of red tide algae in the seaweed family, which proliferates violently under specific environmental conditions due to special environmental conditions, so that some red tide organisms over-multiply, will form red tide. The proliferation of red tide organisms to reach a certain density is the primary condition for the occurrence of red tide.
2. Causes of red tide
a. Changes in hydrometeorology and physical and chemical factors of seawater are important reasons for the occurrence of red tide. The temperature of seawater is an important environmental factor in the occurrence of red tide, and 20 °C to 30 °C is the suitable temperature range for the occurrence of red tide.
b. In the range of salinity between 26 and 37, there is a possibility of red tide.
Due to the confluence of runoff, upwelling currents, water masses or currents, the nutrient salts of the sea bottom rise to the upper layers of the water, resulting in high eutrophication of coastal waters.
3. On the other hand, a large amount of sewage is discharged into the sea, and the pollution of marine aquaculture is also one of the factors that induce red tide. Natural factors are also an important cause of red tide, and in addition to human causes, the frequent occurrence of red tide is also related to natural factors such as latitude location, season, ocean currents and the degree of closure of the sea area.
4. The hazards of red tide disasters
a. Destroying the ecological balance of the ocean.
(b) Destruction of marine fisheries and aquatic resources.
c. Endanger human health.
4. Some red tide organisms can also secrete some toxins that can accumulate in shellfish, collectively known as shellfish poison. At present, it is determined that more than 10 kinds of shellfish venom toxins are 80 times higher than cobra toxins, and more than 100,000 times stronger than general anesthetics such as procaine and cocaine.