Natural disaster is a natural event such as a flood, earthquake, drought, landslides, volcanic eruptions or hurricane that causes great damage or loss of life (see the above image).
Earthquakes are sudden vibration or tremors on the surface of the earth. Earthquakes can be both minor and major in intensity. Major earthquakes are the most dangerous, widespread and destructive of all natural disasters.
Why Earthquake Occurs?
Earthquakes occurs when two large pieces of the earth’s crust suddenly slip. When this slip happens massive energy moves through the earth in the form of waves, which we feel and call an earthquake. Earthquakes are the most deadly of all natural disasters. Strong earthquake can destroy entire city. Over 10,000 people die every year in earthquakes.
The place on the surface of the earth where the earthquake is strongest is called epicenter. Therefore places close to epicenter suffer maximum damage.
It is very difficult to accurately predict the earthquakes. People living in earthquake-prone areas should build houses that can withstand earthquakes tremors. During earthquake people should quickly leave their houses to be in an open place to remain safe.
A cyclone is a powerful spinning storm that forms over warm oceans. In a cyclone strong winds move in a circle and is often accompanied by heavy rain.
Why Cyclone Occurs?
Cyclone occurs when air over the ocean becomes warm very quickly and move upwards. Then cooler air rushes in to take its place. This fast moving air swirls around in a circle to form cyclone.
Cyclone form over the ocean and move towards coastal areas. When a cyclone hits land, it brings heavy rains and strong winds. These strong winds can destroy buildings and uproot trees. Sometimes cyclones causes flood also.
In India, cyclone-prone areas are Odisha, Andhra Pradesh and Tamil Nadu. Cyclones have different names around the world. In North America and the Caribbean it is called hurricanes. Cyclones that form near the Philippines, Japan, and China are known as typhoons. In Australia, it is called willy-willy.
Thus, a cyclone, a hurricane, a typhoon and a willy-willy are all same. The only true difference between a cyclone, a hurricane, a typhoon and a willy-willy is where in the world the storm is!
Flood is a sudden flooding of water in low lying dry areas due to heavy rain. During raining season many parts of India get flooded. Flood cause damage to roads, buildings and crops. In India every year thousands of people and animals loose their live due to floods.
Why Flood Occurs?
Flood occurs when due to heavy rain the water level in the river keeps rising. When the rivers do not have the capacity to hold excess water, these excess water flows over the river bank and floods the surrounding areas. Flood causes damages to property and lives. In villages, crops get damaged due to flood and farmers suffer huge losses. If flood remains in an area for longer time it can contaminate the drinking water and can cause waterborne diseases like cholera.
In India, some states like Assam and Bihar experience regular floods.
Droughts happen when there is not enough rain for a long period of time. As there is no or little rain during drought, the crops get damaged. It also causes scarcity of drinking water.
Why Drought Occurs?
Failure of monsoon over several years causes drought. Farmers cannot irrigate their crops as the land dries up due to shortage of rain fall. They suffer huge loses as the crops get damaged due to shortage of water. Due to damage of crop there is shortage of food in that area.
In India, parts of Maharashtra, Andhra Pradesh, Gujarat and Rajasthan receives very little rainfall and are thus drought-prone areas.
A volcano is a mountain with a large opening at the top through which hot molten rock and gases are forced out into the air. When these are thrown out with great force, it is called volcanic eruption.
What Causes Volcanic Eruptions?
When the heat inside the earth creates huge pressure volcanic eruptions take place. The molten rocks and gases burst out through weak cracks on the earth’s surface called vents. Over the period of many years and with repeated eruptions, molten rocks or lava cools down and hardens forming a cone-like structure called volcano around the vent.
Types of Volcanoes
Active volcanoes: They are the volcanoes that have erupted recently and are likely to erupt again.
Dormant volcanoes: They are the volcanoes which were active in the past but have remained quiet in recent times.
Extinct volcanoes: They are the volcanoes which have not erupted for many years.
Some more important topics of CLASS 5