Natural Disaster: a natural event such as a flood, earthquake, or tsunami that kills or injures a lot of people.
Noun: Europe's 2003 heat wave claimed more than 30,000 lives, making it the continent's largest natural disaster in 50 years.
Drought: a long period when there is little or no rain.
Noun: This year (a) severe drought has ruined the crops.
Earthquake: a sudden violent movement of the earth's surface, sometimes causing great damage.
Noun: In 1906 an earthquake destroyed much of San Francisco.