After a volcanic eruption, lava flowed over an area and then cooled to form a thick layer of new rock. One thousand years later, a thriving forest with diverse flora and fauna is found in that area, even though evidence suggests that several large forest fires have occurred. Which statement best describes what happened? Secondary succession occurred, followed by several primary successions. Only secondary successions occurred. Primary succession occurred, followed by several secondary successions. Only primary successions occurred.

The statement that best describes what happened is: "Primary succession occurred, followed by several secondary successions."

Here's why:

1. Primary succession: This is the series of community changes that occur in an entirely new habitat which has never been colonized before. In this case, the volcanic eruption and the subsequent cooling of lava to form a new layer of rock created a new, lifeless area. Over time, life began to take hold starting with hardy pioneer species (like lichens or certain types of hardy plants) that are capable of living in such harsh conditions. Over hundreds of years, these species gradually changed the environment (like improving soil quality), making it possible for other, more complex life forms to move in and establish a community. This process continued until a stable, self-sustaining community (a forest, in this case) was established. This is primary succession.

2. Secondary succession: This is the series of community changes which take place on a pre-existing, colonized but disturbed or damaged habitat. Examples include areas which have been cleared of existing vegetation (such as after farming) or destroyed (such as by fire). In this case, the forest fires that occurred after the forest was established would have destroyed the existing community, but not all life and certainly not the soil. This means that the process of re-establishing the community would have been faster than the primary succession, as it wouldn't need to start from scratch. This is secondary succession.

So, the process was: a primary succession (to establish the forest), followed by several secondary successions (after each forest fire).