1. Avalanche — It is a fall or slide of a large mass as of snow or rock, down a mountain side.
2. Tsunami — It is a long, high sea wave caused by an undersea earthquake or other disturbance.
3. Epidemic — It is an outbreak of a contagious disease that spreads rapidly and widely.
4. Storm surge — It is an abnormal rise in the level of the sea along a coast caused by the onshore winds of a severe cyclone.
5. Water table — It is the level below which the ground is saturated with water.