[Island Chris]

There is a nice analogue experiment going on the roof of our house on the island. We have solar shingles, which have low friction coefficient, and we have regular shingles below the solar shingles, which have high friction coefficient. We have a 15 cm of heavy wet snow. It starts to creep down the solar shingles, adding shear stress to the shear stress from gravity (as resolved onto 27 degree dip of roof). Then, we have sudden, violent avalanches, which last about 1 to 2 s, and I think could injure someone if they were on our deck. This is essentially a snowquake.

A bit more than half of the solar shingles avalanched 2 days ago.
The other side has slid a half meter at the top, on the solar, but is stuck on the regular shingles at the bottom. The shortening in between has created a fold and thrust belt in the snow.

The odd thing is that our last two snow quakes were within two minutes of the same time, about a week apart: 2:01 PM local time and the 1:59 PM local time. We know this because we bet on it.

Chris

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The snowquake of the rest of our roof just occurred, at 4:23 PM local time. A bit less violent than the last one, but kind of impressive anyway.

Chris