[extropy-chat] Volcanic diamond eruptions

[John K Clark]

I have a question about geology that I have not been able to find an answer
to. We've all heard that diamonds come from volcanoes, but no modern volcano
produces diamonds. The Tambora eruption in 1815 made a year without a summer
but it couldn't make a single diamond, even the Yellowstone eruption 2
million years ago that was far larger than anything in recorded history did
not produce diamonds. The super colossal eruption in India 65 million years
ago managed to produce the second largest lava flow on the planet called the
Deccan Traps, but it couldn't produce diamonds; the very largest lave flow
is the Siberian Traps formed 251 million years ago, but again no diamonds.

I had heard that the roots of a volcano that produced diamonds must go much
deeper into the earth than normal volcanoes, and lava had to screams out of
them with much much greater speed than your average vanilla volcano. I had
assumed that sort of eruption only happened billions of years ago, after all
the earth's interior was much hotter then; and indeed most diamond deposits
are very old. But not all. The volcano that produced the Ellendale diamond
field in Australia erupted only 20 million years ago.

I don't get it. The Siberian eruption 251 million years ago was so huge it
is a likely candidate for causing the greatest mass extinction of all time,
but it produced no diamonds. The eruption In Australia 20 million years ago
must have ejected gas and lava at enormous speed, far greater speeds and
from far greater depths than any eruption a human being has ever seen, yet
it produced no big extinctions. I just don't get it. I hope we have a
geologist on the list.

  John K Clark    jonkc at att.net