Darwin Point

Darwin Point

Darwin Points are drowning thresholds for coral reefs and coral islands that have existed in the world oceans since the evolution of reef building corals at the beginning of the Mesozoic Era ~240 Ma (Grigg, in press). A Darwin Point is reached when the net production or vertical accretion rate of CaCO₃ by reef building corals no longer keeps pace with relative sea level. A Darwin Point is exceeded when the reef structure permanently drowns. Drowning occurs when production rates due to coral growth are exceeded by rates of bio-erosion, physical-induced losses, rates of island subsidence, or sea-level rise. During the last transgression, the sea level rose on the order of 130 m (21,000 years B.P. to the present), and many coral reefs in the world drowned. Another classic example where a Darwin Point exists is the northwestern end of the Hawaiian Archipelago (Grigg, 1982) (see Figure 2 in the entry Hawaiian Emperor Volcanic Chain and Coral Reef History ), beyond which atolls...