Bizarre Features

The-Great-Wave-off-Kanagawa-by-Hokusai-coloring-page

“According to the team’s modeling, the waves near the point where the asteroid struck would have been approximately 300 metres tall. When they hit the coast they wouldn’t be quite that big, but would still have reached 75 or 80 metres, Costard says.

“The most probable source of the tsunami, the scientists concluded, is a 60-kilometre impact crater located about 1000 kilometres off the putative coast. But it is also possible that the deposits could have been produced by the combined results of two independent impacts, represented by smaller craters closer to the shore.

“The new research also explains bizarre features known as thumbprint terrain, on the seaward ends of some of the tsunami deposits. Composed of curving, concentric ridges 10 to 20 metres high, these look for all the world like the ridges in a fingerprint.

“The explanation, Clifford says, starts with the fact that the tsunami would have come in two pulses. The first would have been produced when the asteroid hit, shoving tremendous amounts of water out of its way. The second would have occurred when water rushed back into the resulting depression from all sides.

“The onrushing water would have crashed together in the centre of the impact depression in a giant splash, then rebounded outward in a second tsunami, even larger than the first.

“And that’s just the beginning of the story. When the first wave, a few minutes ahead of the second, hit the shoreline, part of it would have been reflected back out to sea. There, it would have met the oncoming second wave, where the turbulence would have caused sediment to be dropped in patterns exactly like the enigmatic thumbprint terrains.”

Text: Mars may have experienced a giant tsunamiCosmos Magazine.

Image: The Great Wave Off Kanagawa By Hokusai, Supercoloring version.