Primary succession is a type of ecological succession that occurs in the areas where no life ever existed. It includes regions such as bare rocks, where the soil is unable to sustain life. Primary succession can occur due to a number of events such as volcanic eruptions, oil spills, floods, the retreat of glaciers, etc. These activities leave the bare rocks exposed and accessible to a variety of new species that can colonize there. These species are known as the pioneer species. After the pioneer species, the intermediate species such as plants and other organisms alter the soil composition and the habitat they colonize. Finally, the climax community is obtained where larger and more complex organisms can survive.