A process in which huge numbers of species on a Garden World die out suddenly. Divided into (from most severe to least):
The K-T extinction removed the dinosaurs; the P-Tr extinction eliminated 95% of all kinds of Terran life, the Fr-Fa (Devonian period) killed coral reefs and many types of invertebrates. Mass extinctions are caused by a variety of factors, but are often triggered or exacerbated by bolide impacts.
- Class 10 - all life destroyed
- Class 9 - all surface life (even microbial) destroyed; rare microbial life survives deep in the crust.
- Class 8 - most life destroyed; some microbial life survives in sheltered environments
- Class 7 - all higher life destroyed; hardy microbial life survives
- Class 6 - almost all complex life destroyed; microbial life survives
- Class 5 - most species and groups of organisms killed - P-Tr equivalent
- Class 4 - many species and groups of organisms killed; others survive - K-T or Fr-Fa equivalent.
- Class 3 - many species extinct, but most major groups survive - late Triassic, Mid Cretaceous, or End Eocene turnover
- Class 2 - some species extinct but many survive - minor extinction events
- Class 1 - susceptible and vulnerable species die out; all others survive - local forest clearing, medium climate change events
Generally, the highest extinction classes (anything higher than 6) result only from pernicious goo swarms or nearby supernova explosions. Class 10 is extremely rare; life is amazingly hardy. However, fragile, complex biospheres are easily disrupted, and any development automatically results in a class 1, even a class 2 extinction.
The great ecological crisis of the Industrial/Atomic/Information Age Old Earth was a Class 4.8 event, one of the most destructive on record (only actions like the deliberate "salting" during the Empires war, and again during the Sagittarius-Softbot war, are more thorough).