Coral atolls ring lagoons after volcanic islands slowly sink
Darwin’s insight still holds: fringing reefs grow around volcanic islands; as the island subsides or sea level rises relative to the rock, the reef becomes a barrier, then a ring — an atoll — around a central lagoon.
Coral keeps building upward toward the light while the original volcano vanishes beneath waves. Drill cores find volcanic rock deep under many Pacific atolls.
An atoll is a graveyard of a mountain wearing a living crown. Reefs outlast the island that first gave them a foothold.
Comments
0 comments