Final answer:
This is an example of primary succession, where mosses and lichens, acting as pioneer species, colonize new volcanic land and contribute to soil formation.
Step-by-step explanation:
The scenario described where mosses and lichens began to grow on the bare volcanic rock after an undersea volcano erupted and formed a small island is an example of primary succession.
This type of ecological succession occurs on land surfaces where soil has not yet formed. Lichens and mosses, as pioneer species, are often the first to colonize these new lands because they don't require soil to grow; instead, they contribute to soil formation by breaking down the rock into smaller particles which can eventually support other forms of plant life.