Mainly floods and droughts.
If a natural disaster occurs it is highly unlikely you would need to call anyone.
A tornado is both. A calamity is a disaster. A tornado is a disaster that occurs naturally, and would thus be consideted a natural calamity or natural disaster.
because it occurs naturally.
flooding
After a natural disaster occurs in a healthy ecosystem, secondary succession will cause the ecosystem to return to its original Climax Community.
national guard
Floods in Brazil Floods in Australia
The Correct answer is Flooding
earthquake and related tsunami.
hurricane
The natural disaster of volcano eruptions often take place.
There is no prevention for this as it occurs inside the earth and we cannot have a control on it.