Which event is likely to initiate primary succession?

Primary succession is the process by which a community of organisms develops in a previously uninhabited, barren environment, which typically has no soil or organic matter. A volcanic eruption serves as a classic example of an event that can initiate this type of succession. When a volcano erupts, it can create new landforms, such as lava flows, that are devoid of life and soil.

After the eruption, the first organisms to colonize these areas are usually pioneer species, like lichens and mosses, which can thrive in harsh conditions and begin to break down solid rock. As these organisms grow and die, they contribute organic material to the substrate, gradually developing soil. This process allows for more complex plants to establish themselves over time, leading to increased biodiversity and the eventual formation of a mature ecosystem.

In contrast, events like overgrazing, species extinction, or the introduction of invasive species may disrupt existing ecosystems but do not create the conditions necessary for primary succession to occur. Instead, they can lead to secondary succession, where life returns to an area after disruption, but the soil is already present. Thus, a volcanic eruption is the most accurate answer to identify an event that initiates primary succession.