I'm surprised that around 5900 B.C. it was apparently more warm than now. At least this is what is suggested by the fact that at that time the glacier didn't cover that crystal vein.
I read it as the vein having been exposed by the movement of the glacier advancing, taking everything that was previously above the vein with it and exposing it to the surface.
I didn't think the glacier was necessarily present in 5900 BC.
Now that I've gone back and re-read the article, it looks like I was mistaken:
> [H]e came upon a rich vein of rock crystal exposed by a retreating glacier.
> The team determined that hunter-gatherers living during the Alpine Mesolithic period (ca. 9000–5500 B.C.) visited the site as recently as 5900 B.C. and extracted rock crystal from the vein, after which it was covered by the advancing glacier.
The article seems to be saying that the glacier both advanced over the area and retreated from it since 5900 BC. That might mean it was warmer then than it is now, but not necessarily - the "recent" glaciation could have been caused by differences in climate other than temperature, like precipitation.
Hypothetically, it could be that it has been warming since 5900 BC. Prior to that, the glacier could have existed but been relatively static at higher elevation. Warming would have caused some to melt, which changed the forces at play and caused the glacier to migrate down the slope. That would have allowed the vein to be accessible in 5900 BC, covered at some point thereafter by the movement of the glacier, then be accessible again today due to the glacier melting and/or continuing its movement to lower elevations.
There's just not enough information in the article to say for sure, and I'm not familiar enough with the state of our knowledge of historical climate data to make an educated guess.
> .. and extracted rock crystal from the vein, after which it was covered by the advancing glacier.
I think you read wrong. It says it was covered by the advancing glacier, not uncovered.
So at 5900 BC the glacier had advanced less than now and certainly a lot less than say 100 years ago. Doesn't this mean that it was warmer at that time, or at the very least, warmer some time not too long before 5900 BC?
Glaciers slide down hill. As they accumulate mass in the accumulation zone, even when it's cold, they are pushed down the hill. So a glacier which is growing in size will still be moving down hill.
Its on average around 0.5m/day, but could be up to 1m/day. Gravity is too strong force, and they are not tightly bonded to bedrock. I would expect that in hard winter they move much less but still some.
That's how they keep discovering dead alpinists (more like parts of them, ie Reinhold Messner's brother Gunther on Nanga Parbat who died there in 1970, I think it was piece of femur bone and shoe) in Alps and Himalaya, everything that falls down on glacier or into crevasse eventually ends up at the snout of glacier (or river flowing from it).
Their overall accelerated melting due to climate change just accelerates all this since glaciers retreat higher and higher.
Yes it flows downhill, but as long as ice is accumulated in the accumulation zone, which is in the upper region of the glacier, the downflowing part is filled up by new ice from above.
By the way the article doesn't say that the veins were uncovered by the advancing glacier, it says the opposite, the advancing glacier covered them.
