Which environmental change occurs most rapidly?

volcanic eruption

Explanation:

"The environmental change that occurs faster is definitely volcanic eruption. It may happen in an instant and destroy everything in its way, whereas the process of regrowth of forest after volcanic eruption is a slow one."

Abrupt climate change.

Explanation:

Abrupt climate change is climate change that occurs relatively rapidly. Our understanding of past abrupt climate changes and their causes is still in its infancy; most of the research on this topic has occurred since the early 1990s.

the fossil record provides evidence of a common ancestor to many species.