Extinction Distinction
Background extinction or mass killing?
(McLaren and Goodfellow, 1990)
Which mechanism has been dominant at specific times in Earth
history?
- Slow-acting extinction model: identified by taxa changes;
biological mechanisms and response apparently understood, but forcing of
gradual environmental change is debated:
mantle-movement, solar system changes, climate, sea-level changes, and
ocean chemistry -- impacts assigned a minor role.
- Catastrophic kill model: based on biomass disappearance at a
bedding plane (extremely short duration of initial events, years to 100
years); cause is debated: mantle-movement, solar system
changes, climate, sea-level changes, and
ocean chemistry -- impacts historically assigned a minor role
