Primary succession will begin after the following:
A) Glaciation (Continental glaciers & Alpine glaciers) - Plants and other life colonize the bare rock.
B) Volcanic Lava Flows - Ex.: Hawaii, Columbia Basalts of ancient Oregon.
C) Volcanic Explosions - Mt. St. Helens, Mt. Mazama (Crater Lake)
D) Faulting raising sea floor -
All of the above examples provide pioneer plants with bare rock or soil to begin succession with.