The impact winter
Sulfate aerosol blocks the sun for years, photosynthesis stops, and the food chain collapses from the bottom.
- When
- Known to
- ± 50 thousand years
- Era
- Cretaceous, Mesozoic
The immediate kill mechanism is not the blast but the darkness. Sulfate aerosols and soot loft into the stratosphere and cut sunlight enough to halt photosynthesis for months to years, with surface cooling of many degrees. Marine plankton crash, and the food webs resting on them go with them. On land the boundary is followed by a fern spike — a layer where fern spores dominate the pollen record, the signature of a devastated landscape recolonised by the first opportunists. Recent work argues dust and soot mattered more than sulfur.