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Comment by duncancarroll | Hacker News Reader

Still not quite sure how the trails themselves are formed if the rocks are riding on ice sheets 10's of meters in area, or am I reading this wrong / quickly?

Edit: n/m, it appears the ice sheets are massive and free-of-friction enough to actually push the rocks around. Cool!

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The rocks are on the ground, not the ice. They are surrounded by floating ice sheets. But the ice sheets are gigantic and I assume the massive surface area combined with the right amount of wind friction generates enough force to push the rocks. (Of course now I'm wondering why the ice sheets don't buckle, especially in the spots where they abut the rock.)

Good question. Perhaps the pressure at any given point of contact is too low to cause the ice to buckle, but there's enough surface area of the rock in contact with the ice for the aggregate force to be large.

> ice sheets don't buckle

Ice is quite strong, especially in compression.

To buckle the ice (i.e. flexure strength) you would need enough force to lift the ice both against gravity and against the air pressure holding it to the water below.

Maybe the sheets do break, but that doesn't stop them:

https://www.youtube.com/watch?v=fqptbtwXUCs

The rocks are embedded in the ice. Imagine the rocks are wearing really large ice "skirts" which mostly float over a layer of water, but the bottom point of the rock still contacts the ground.

Edit: Nope, not embedded, just pushed.

Actually they don't embed themselves in the ice, the ice is free floating with very little friction on top of the water and pushes the rocks using inertia from the wind.

"Lorenz (one of the co-authors of this piece) has disproven his previous theory--that the rocks were temporarily embedded in a slab of ice which then floated."

Whoops, missed that.

They are not "riding on" but rather being "pushed by" the sheets of ice.

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