In a lodgement till the long axes of the stones line up with the ice. Measure fifty of them and the orientation tensor says how strongly — and whether what you are standing on was dragged under a glacier or dumped out of one.
A glacier and a river both make gravel, and they make it differently. Ice breaks stones and carries them without turning them; water rounds them and flattens them. Shape and roundness together tell the two apart when nothing else does.
A glacier flows because its own weight drags it downhill. The driving stress is ρgh sin α, and for almost every glacier on earth it comes out between 50 and 150 kilopascals — which means you can work backwards from a moraine's slope to how thick the ice was.
How deep does the ground freeze, or thaw? Freezing is limited by getting the latent heat out, so the depth grows as the square root of the accumulated cold — not in proportion to it. Twice the winter gets you only forty per cent deeper.
Striae give the line the ice travelled. They do not give the direction — a scratch looks the same from both ends. These do give it, and any one of them settles what a hundred striae cannot.
| what to look for | which way the ice went |
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Cross-cutting striae are two flows, and the one that cuts is the later. Record both with their bearings — the pair is worth more than either alone, because it dates a change in the ice sheet.
The fabric maths here is the same orientation tensor that Structural analysis uses on poles to bedding — clasts in a till and planes in a fold are the same problem wearing different clothes. Grain size of the matrix, which separates a lodgement till from a flow till, is in the Loupe.