From Douglas Turnbull
Townsville, Queensland, Australia
Further to the two letters on the Great Dinosaur Extinction (Letters, 14
September, p 52), both of your correspondents suggested that the impact of an
asteroid hitting the Earth could have caused a lava pulse on the opposite side
of the planet, one suggestion being the Deccan Traps as the antipodes of the
Yucatán impact 65 million years ago.
There is a precedent for that in the Solar System. Mercury has an area of
tectonic movement in the vicinity of the crater Petrarch, which lies at the
antipodes of the Caloris Basin. The Caloris Basin was produced by an enormous
impact, and the area of tectonic movement is a chaotic jumble of fractured
terrain, associated with substantial volcanic eruptions. A description of this
feature can be found in the Cambridge Atlas of Astronomy, 1985 edition,
p 69. The authors suggest that seismic waves produced by the Caloris impact were
focused towards the antipodes of the planet.
