Rockslide and Landslide: (deslizaminetos)
NATURAL DISASTERS
A disaster is an event that could hurt people and cause damages.
Tornadoes: it is a violent wind movement. They are also called twisters or cyclones. Most people recognize them as a towering black funnel extending downward from the base of a large cumulonimbus cloud. It rotates at speeds up to three hundred miles per hour (480 kpm) or in some rare cases, even faster. In the center of the tornado, the air pressure is very low in comparison to surrounding air pressure.
The speed of the wind is the primary cause of deaths and destruction of property. Many people are killed by flying objects and debris (missiles). They happened In certain parts of the world Australia, the Midwestern and Southern of United States
They also occur more frequently in the spring and summer months. Tornadoes usually occur as part of a severe thunderstorm and often come in advance of cold fronts, however, they can also occur (although less frequently) ahead of warm fronts, and even behind cold fronts.
The greatest killer tornado in the United States occurred during the year 1925 in Indiana, Illinois, and Missouri. It killed six hundred ninety five people and injured over two thousand.
Hurricanes: they are one of natures many destructive forces. The word comes from West Indian; huracan ("big wind"). Hurricanes are seasonal storms and are most prevalent in August and September. They develop from easterly waves, which can later develop into a tropical depression with winds up to 31 miles per hour. Later, it might develop into a tropical storm with winds up to 73 miles per hour, and eventually a hurricane. Thunderstorms often form with hurricanes and then produce waterspouts.
Hurricanes are huge tropical cyclones that originate over oceans near the equator, such as the Caribbean Sea and the Gulf of Mexico. However, if they do reach land, destruction of property is imminent. Wind speeds of a hurricane range from seventy to one hundred fifty miles per hour.
One of the most destructive elements of a hurricane is the huge waves that are formed because of the strong winds and heavy rains. These waves called a storm surge can rise several feet above water levels, especially during high tide.
"Tsunami" is the Japanese word meaning tidal wave. A tidal wave is a large sea wave caused by a submarine earthquake or volcanic explosion. When the ocean floor is tilted or offset during an earthquake, a set of waves is created. These waves are similar to the concentric waves generated by an object dropped into the water.
Usually tsunamis move entirely across an ocean to the shore. A tsunami can have wavelengths of 60 to 120 mi and may reach speeds of 800 km/h. When the wave enters shallow waters, the wave, which may have been half a meter high out at sea, grows rapidly. When the wave reaches the shore, it may be 50 ft. high or more. Tsunamis have incredible energy because of the great volume of water affected.
|
|
|
Since the year 1819, more than 40 tsunamis have struck the Hawaiian Islands. A tsunami warning system has been developed in areas such as Hawaii, where many devastating tidal waves occur. Hawaii, the highest risk area, averages one tsunami every year with a damaging occurrence every 7 years. Since 1945, more people have been killed as a result than as a direct result of an earthquake's groundshaking.
Lightning: Lightning is characterized by the discharge of electricity between rain clouds or between a rain cloud and the earth. It is usually seen as an arc of extremely bright light which can be many kilometers in length; however, there are other forms as well. Accompanying the lightning is the giant roar of thunder. The thunder is caused by the expansion of air that has been heated by the lightning which then collides with cooler air, creating the sound of an explosion.
Thunderstorms are the most common types of storms, and thunder itself, although frightening, is not dangerous. It is the lightning that causes the problems. Lightning and thunder occur together, however we hear the thunder after we see the lightning. Sound waves travel about one mile in five seconds, while light travels at more than 186,000 miles per second. Therefore, lightning is seen immediately when it occurs, and thunder is heard a little later.
The different sounds of thunder (deep roar/loud crash) is caused by the different types of lightning, for example, the thunder that has the sharp crackle like sound is caused when the large trunk of lightning forks into many branches.
 |
|
|
|
Earthquake: is a shaking of the ground caused by the sudden dislocation of material within the earth's outer layer, or crust. When forces pushing on a mass of rock overcome the friction holding the rock in place and blocks of rock slip against each other a earthquake may occur. Some earthquakes are so slight, and some occur in such remote areas, that they are barely felt. Others are so violent that they cause extensive damage.
Earthquakes are caused by stresses below the earth's outer surface. These stresses usually build up until the rocks fracture along a "fault plane." This causes vibrations, also known as seismic waves. Seismic waves will then travel in all directions from the area of fracture. In large earthquakes seismic waves may be detected over the entire earth.
Earthquakes can be caused by volcanoes in certain cases. Nuclear explosions under the ground can create waves that are very similar to natural seismic waves. The seismic energy created in a atomic bomb is one hundred-thousandth that of the largest earthquake.
Earthquakes take place or have taken place in all parts of the world. Frequent activity occurs along certain belts. 80% of all seismic energy is generated from a belt that is found at the border of the Pacific Ocean. The intensity of an earthquake is measured in terms of its geological effects and the overall damage it brings. There are two major scales in which earthquakes are measured. These two scales are the Mercalli Scale and the Richter Scale.
Avalanche: they occurs when a mass of snow falls down a mountainside. That is because new snow (which is not wet) accumulates on a more heavy snow layer. Since the new snow layer is not compact, it could slide down toward the base of the mountain.
Avalanches could be triggered by loud noise (yells, firearm shots, etc.). Skiers, snowboarders and climbers could also cause an avalanche.
There are two ways to reduce avalanche risks: by installing snowsheds or by triggering controlled avalanches. These protection fences are made of rocks, soil and other materials. They prevent avalanches to fill trails used by humans.
|
|
|
Controlled avalanches cause the accumulated snow to fall down before it could trigger avalanches by itself. When nobody is in danger, explosives are used to produce a loud noise that causes an avalanche.
 |
Wildfires: (incendios forestales) they are dangerous for all people living near woodlands.
In the wild, wildfires are ignited by lightning. But some wildfires are caused by careless campers who did not extinguish their campfire or by walkers who threw their cigarettes in the woods. 80% of wildfires are caused by careless people. Wildfires move forward rapidly, even more if winds blow and the weather is dry. To stop wildfires, firefighters use water bombers which carry water and drop it on wildfires. Wildfires do not only have bad effects. In fact, the many dead pin needles, leaves and tree trunks on the ground are burnt to ashes by wildfires. These ashes are full of minerals and help the growth of new trees. By burning trees, wildfires make “gaps” in the forest (called clearings). These clearings allow the sun to heat the ground up and help tree seeds to grow.
 |
Floods: they happen when a watercourse overflows. They could be caused by rain, thaws or ice jams.
Heavy Rain: when it rains, water falling on the ground penetrates it. But when the ground already contains a lot of water, the falling rain could not seep through it. The water then starts flowing toward a watercourse. When it rains a lot on a region, all water flows toward the river, but this river can not contain it; therefore, the river overflows.
Thaw: when spring arrives, snow and ice start to melt and the water flows toward the river. If the temperature rises too rapidly, a lot of water is produced in a short time; the river overflows and a flood happens.
Ice Jam: In spring, rivers thaw out and big chunks of ice detach themselves and drift on the river. Sometimes these chunks get jammed against a bridge or rocks. Consequently, these chunks of ice form a kind of dam.
|
|
|
When water can not flow through this dam, it tries to find an alternate course to reach the river… and, sometimes, this new course is a field, a road or a house basement.
Rockslide and Landslide: (deslizaminetos)
Rockslide is a downward and rapid movement of newly detached pieces of bedrock.
Landslides are ground and rock movements. They occur most commonly where the ground is made of soft material, like clay.
When ground or cliffs collapsed, one calls them "scree".
The difference between a rockslide and a landslide is what is sliding:
Дата добавления: 2021-05-18; просмотров: 77; Мы поможем в написании вашей работы! |
Мы поможем в написании ваших работ!