In ecology, catastrophes permanently alter the physical structure of the existing environment.
<u>Explanation:</u>
The ecological disturbances include flood, strom, plague, fires, earthquakes, tsunami, volcanic eruptions, climatic change and impact of humans on the environment like deforestation ,nuclear testing etc.
These factors can have a visible impact on the structure of the earth and permanently alter the environment.
The visible effects of these disturbances are global warming, extinction of selective species, change in the course of rivers, submergence of coastal areas, sudden movement of the tectonic plates and formation of sudden cracks on the earth's crust.
