Which event is an example of secondary succession?

Secondary succession refers to the ecological process that occurs in an area that has been disturbed but where soil and some organisms still exist after a disturbance. The event that exemplifies this process is flooding of an area. When flooding occurs, it can temporarily alter the landscape and displace existing vegetation, but the underlying soil usually remains intact, allowing new plant life to eventually grow back more quickly than in primary succession, where soil formation would be necessary.

The other events mentioned represent different types of ecological impact. A volcanic eruption typically leads to primary succession, as it can create new land that lacks soil and vegetation. The retreat of glaciers also promotes primary succession—the land exposed may have no soil initially, necessitating a gradual building up of ecological communities over time. The formation of bare rock is another initial stage that sets the stage for primary succession, as there is no organic layer present to support life initially. Thus, flooding is the best example of secondary succession in this context.