South African rocks reveal that a huge asteroid smashed into Earth 3.26 billion years ago, turning sediments to liquid.

The rocks in the Barberton greenstone belt in South Africa contain tiny blobs of material that condensed from clouds of rock vapour generated by ancient impacts. Norman Sleep and Donald Lowe of Stanford University in California used those blobs, along with other features of the Barberton rocks, to calculate the size and geological effects of this particular asteroid impact.

The duo found that the asteroid was probably 50 kilometres across. Seismic waves from the impact fractured much of Earth's crust, triggering strong earthquakes and giant tsunamis, the authors say.

Geochem. Geophys. Geosys. (2014)