Was anyone in the way of a landslide in the Himalayas liberating 6 cubic miles of rock (24 cubic kilometers)?
It happened in Nepal on the 8000-meter peak Annapurna IV, right about the year 1190. The peak of the mountain massif sheared off all at once. The rubble crashed down the valleys for 150 km; rivers were dammed and rerouted. It’s all visible, though recently discovered.
To set the date, Jérôme Lavé and 11 colleagues from France, the US, and Nepal tested the remains of plants trapped in the vast rubble. They have been carbon-dated from the natural carbon-14 radioactivity taken up from the air by the plants while they were alive. Second kind of evidence: natural radioactivity in rocks creates lattice damage while sunlight bleaches out the damage. A rock buried from the sun accumulates damage centers over time. Shining infrared light on it triggers light to be emitted in proportion to the time the rock has been buried.
The research yields the story that the super-tall mountains can escape the mild flake-by-flake erosion from freeze-thaw cycles. Their peaks can stay intact if they stay super-cold, getting higher and higher. However, Annapurna IV rather suddenly freeze-thawed during the warm Medieval Climate Anomaly, cracking in a phenomenal way. More warming is in progress, so, watch out!
This has been an outreach activity of the Las Cruces Academy, viewable at GreatSchools.org
