Analyze the mechanisms of primary and secondary successions. What is their difference?

Primary successions begin at a place previously deprived of life. For example, on frozen lava after volcanic eruptions, on sea islands after earthquakes, on sand dunes, on bare rocks, river deposits. Secondary successions begin at the site of the destroyed ecosystem. An example is the overgrowing of abandoned fields, deforestation, polluted water bodies, restoration of meadows and forests after a fire, drought, flood, erosion.