Two Categories of Fatalities. Two Timescales. One Catastrophic Event.

Extinction rates serve as a reliable yardstick for measuring the true scale of a catastrophic impact event - and Randall’s reasoning is precise. Loss of species is directly proportional to loss of habitat, which means the pattern of extinctions in the geological record provides a measurable proxy for the geographic reach and intensity of whatever caused them. A bolide impact will produce immediate mass extinction within a defined radius determined by the overpressure generated at the moment of impact and how quickly that overpressure dissipates with distance.

However the immediate fatalities are only the first category. Randall identifies a second category that plays out across a very different timescale - the aftermath. The months following a major impact event can produce fatalities that rival or exceed the instantaneous destruction, as habitat collapse, climate disruption, and ecosystem failure ripple outward from the initial event. The extinction record Randall is reading is not simply a measure of how big the initial blast was. It is the combined signature of both waves - the instantaneous and the prolonged - and understanding the difference between them is essential to accurately reconstructing what actually happened at major extinction boundaries in Earth's history.

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