Know the difference between Natural Hazards and Natural Disasters

 

Natural hazards are naturally-occurring physical phenomena caused either by rapid or slow onset events having atmospheric, geologic and hydrologic origins on solar, global, regional, national and local scales. They include earthquakes, volcanic eruptions, landslides, tsunamis, floods and drought.

Natural disasters are the consequences or effects of natural hazards. They represent a serious breakdown in sustainability and disruption of economic and social progress. 

Earthquakes are vibrations produced in the Earth's crust when rocks in which elastic strain has been building up suddenly rupture, and then rebound. The vibrations can range from barely noticeable to catastrophically destructive. Earthquakes can release energy thousands of times greater than the world's first atomic bomb.

Volcanism, processes by which molten rock material, or magma, rises from the interior of the Earth on to or towards its surface, and by which associated gases are released into the atmosphere. Volcanic eruptions near human settlements can be very devastating. 

Landslide refers to the descent of a mass of earth and rock down a mountain slope. Landslides may occur when water from rain and melting snow sinks through the earth on top of a slope, seeps through cracks and pore spaces in underlying sandstone, and encounters a bed of shale inclined towards the valley. 

Tsunami, (a Japanese word meaning “harbor wave” and used as the scientific term for a seismic sea wave) is a large ocean wave generated by an undersea earthquake. A tsunami is thought to be triggered when the ocean floor is tilted or offset during the quake, creating a set of waves similar to the concentric waves generated by an object dropped into water. Another possible cause is an undersea landslide or volcanic eruption. Most tsunamis originate along the so-called Ring of Fire, a zone of volcanoes and seismic activity, 32,500 km (24,000 mi) long that encircles the Pacific Ocean. Since 1819, for example, about 40 tsunamis have struck the Hawaiian Islands.

But natural disasters are not entirely "natural", for people are agents of disasters. Severe flooding may be exacerbated by deforestation. Many factors combine in the flooding of coastal Bangladesh: temporarily rising sea levels and strong winds caused by the seasonal monsoon; rising of water levels in the Brahmaputra delta caused by deforestation in its mountain headstreams; and densely populated low-lying land on the coastal floodplains. 

 Massive concentration of population in hazard-prone areas or in cities and settlements where houses or infrastructures are not safely constructed or built or where land-use is poorly planned lead to disastrous effects after an earthquake, even at a low scale.

The impact of natural hazards to man can be reduced through better understanding of the geodynamic processes of natural hazards, worldwide dissemination of scientific knowledge, adoption of appropriate public and management policies and increase of awareness Programmes and information campaigns. The application of preventive and preparedness measures such as land-use restrictions, adequate building construction and wise environmental management aims to lessen the devastating effects of unavoidable natural occurring events, and is far cost-effective than recovery and short-term relief or reconstruction and rehabilitation.