FLOOD
A flood is defined as covering of water over land. There are many causes for such condition to arise, and there are different types of flooding. A Flood is commonly called River Flood when there is high flow or overflow of water from a river or similar body of water. Flash Floods are quick-rising floods that usually occur as the result of heavy rains over a short period of time, few hours or less. Several factors contribute to flooding. The two key elements are rainfall intensity and duration. Intensity is the rate of rainfall, and duration as in how long the rain continued. Topography, soil conditions, and ground cover also play an important role. Floods occur within a few minutes or hours of excessive rainfall, a dam breakage, or a sudden release of water held by an ice jam. Flooding is not restricted to specific areas or to a specific country. Certain geographical locations may be more prone to annual flooding from a sudden rainfall.

DROUGHT
A land is considered to be experiencing a drought when there is a prolonged period of abnormally dry weather, either there is little or no rain for an unusually long period of time. A drought can set in when an expected rainfall does not arrive or does not last for long. A drought causes serious hydrological imbalance in the affected area. It is considered to be a weather hazard as people are unable to predict and deal with the consequences of the drought, Not only there is high temperatures and lack of precipitation, but also the agricultural, economic, and sociopolitical impact on inhabitants within the affected region is quite unbearable and hard. Drought areas are warmer than normal for several reasons. One of them is that the dry ground and arid vegetation result in little evaporation, allowing most of the sun's energy to be used in warming the air, resulting in increased temperature, which in turn lowers humidity, making it less likely to rain. The other is lack of rain-producing clouds, which allows more sunshine than normal.

EARTHQUAKE
An earthquake is the result of the sudden movement of two blocks of rock along a break (fault) deep within the earth’s crust. It’s a vibration, on the earth’s surface followed by the release of energy in the earth’s crust. The earth's crust is made up of giant Plates which are thick slabs of rock that make up the outermost 100 kilometers or so of the earth. Most earthquakes occur only in the outer, brittle portions of these plates, where temperatures in the rock are relatively low. Many earthquakes occur when the earth's crustal plates grind and shift along one another. Other earthquakes occur in the middle of the plates and are caused by the geophysical factors. Such factors include, the level of the water table, geological formations including soil and rock deposits over a period of time, or the general stability of the soil and rock in the area. An epicenter is the point on the earth's surface directly above the point inside the earth's mantle that is the focus or the source of the earthquake.

THUNDERSTORM
Any short-lived, violent atmospheric disturbance characterized by thunder, lightning, gusty surface winds, hail, precipitation,etc constitutes a thunderstorm. It is an event of relatively short duration. Water drops from a thunderstorm are small, and they evaporate before reaching the ground as precipitation. Thunderstorms are most likely to occur in a moist, unstable atmosphere. Air masses having these properties are commonly formed over equatorial and tropical areas. Disturbances in the wind field caused by pressure changes in topography lead to an upward displacement of the air initiating the development of thunderstorms. The lightning, which is present in all thunderstorms, is an electrical discharge that balances the difference between positive and negative charges within a cloud, between two clouds, or between a cloud and the ground. Thunderstorms have been known to occur in almost every part of the world. They are, however, rare in the polar regions. It has been estimated that at any one moment there are about 1,700 thunderstorms in progress throughout the world.

SANDSTORM
Sandstorms can be formed when small, light dust particles are blown in to the air, often lifted by the strong winds at the leading edge of a cold front. A sandstorm can rapidly change the appearance of an area with the shifting and re-forming of dunes by the wind. In some drought prone areas, a 'dustbowl' effect can be caused by prolonged drought over a long period because of persistent failure of the rains, and often exacerbated by overgrazing.