This is a plan-view (map-view) field simulation of the same conveyor-belt debris-transport model (Boulton, 1978) used by the 3D version — same ice-speed and thickness profiles along the flowline fraction s (0 = head, 1 = terminus):
v(s) = v_max · sin(π s)
h_ice(s) = h_max · √(1 − s)
The 3D scene renders one extruded ridge cross-section (till thickness varies only along the flowline, uniform across the valley width) viewed from an orbiting camera. This 2D engine instead discretizes till thickness on a full two-dimensional (x, z) grid — downstream distance × lateral position across the valley floor — seen directly from above, like a geomorphological map. Each deposited debris parcel adds thickness only to the grid cell at its own true (x, z) drop point, so the moraine's lateral shape emerges from where individual particles actually happen to melt out, rather than being collapsed into a uniform bar. That is a genuinely different (and finer-grained) computation of the same physics, not a flattened camera angle on the 3D mesh.
Rock debris entering the ice advects downstream at the local surface speed until it reaches the terminus, where it melts out as unsorted till. The terminus itself moves with the climate mass balance: positive advances it (burying/bulldozing till at the front), negative retreats it (which can strand debris in place the instant the ice margin retreats past it). A near-zero balance held for a while lets melt-out debris keep landing at nearly the same downstream position, stacking a sharp terminal moraine ridge; brief stillstands during an overall retreat leave a staircase of recessional moraines.
- Ice surface speed — scales v_max; faster ice delivers debris to the margin sooner.
- Debris supply rate — how often new debris parcels enter the ice.
- Climate mass balance — negative retreats the terminus, positive advances it; hold it near zero to grow a sharp terminal moraine.