EARTH

The Crater That Became a Mine

~1.85 billion years ago

Proterozoic · Paleoproterozoic · Orosirian

An asteroid struck what is now Canada and opened a crater originally some two hundred kilometres across. The blow melted the rock itself, leaving a lake of molten rock ten thousand cubic kilometres in volume on the crater floor. As that lake cooled, the metals it carried, nickel and copper bound to sulfur, were heavier than the rest and sank, gathering at the bottom. That layer is now one of the richest nickel and copper deposits on Earth.

Why it matters

This crater pays for itself. It also lands within a hundred thousand years of the end of the banded iron formations, and some read the two as cause and effect.

Dating & uncertainty

The age is tightly fixed at 1.85 billion years. The original crater is estimated near 200 km across, from seismic imaging of the buried melt sheet; the structure visible today is its deformed, eroded floor.

Sources

1. Wu et al. (1995), Journal of Geophysical Research · Seismic imaging of the enigmatic Sudbury Structure
2. Göllner & Riller (2019), Meteoritics & Planetary Science · Thermo-mechanical interaction of a large impact melt sheet with adjacent target rock
3. Slack & Cannon (2009), Geology · Extraterrestrial demise of banded iron formations 1.85 billion years ago

Earth history as one day

14:13:129 h 47 min before midnight

if Earth’s 4.54 billion years were compressed into a single day