Answer:
After a volcanic eruption, the new landscape that is formed is made up mostly of basalt rock. They are formed when the lava, which contains a lot of iron and magnesium, cools very quickly.
Due to its nature, the only plants or organisms that can grow on the rock at first are usually non-vascular plants like Lichen and Moss.
As these plants go through their life cycle over and over again, dead moss and lichens begin to form humus which is soil.
Gradually, more advanced plants grow on this foundation of dead decomposing moss and lichen. They too go through their cycle dropping dead leaves and gradually inserting roots through cracks that may have formed during the process of weathering.
Soon the big plants (bushes and trees) can grow in those areas.
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