Plans

Erode Lab

Drop a pin anywhere on Earth, then let rain, rivers, ice, creep, faults and uplift reshape it over millions of years.

Start somewhere

Place

Grid detail

Engine

Time

Drag right to run the model forward, left to look into the past (log scale). Run continues forward from where the model has got to; from a past time it runs the model from there to today. Keys: Space run/pause · [ and ] step through time · Home today.

Step size Bigger steps cover deep time faster but blur short events.

Run options steering, past view

Steer to todayEach step nudges the terrain a little toward today's real terrain (barely at first, fully at the end), so the run arrives at today. The result says how much steering the model needed and the Change view maps it. Off by default: the run is the model alone, a test of its skill. Fit start and uplift firstBefore the run you watch, the model runs from the past unwatched, and after each run what it missed at today, in the broad shape only (smoother than 2 km), corrects the next one: as a steady extra uplift where the land stayed land, and in the start's height where the restoration left today's land under the sea. Up to 6 runs, stopping once the miss stops shrinking. Valleys and ridges are left for the model to find. The run then lands closer, but it's no longer a free prediction: the result gives the miss before and after fitting (the extra uplift's numbers are in research mode, ?research=1). That extra uplift is whatever reproduces today's shape, not a measured or predicted uplift rate. At the listed places the fit is prepared in advance, so it takes about as long as a plain run; elsewhere it takes a few runs' time first: up to a minute or two on the GPU, several minutes on the CPU. Starts from the restored past terrain (illustrative) and runs the calibrated model forward to today, then compares it with the real terrain. With both options off (the default) it's the model alone, and the Change view maps where it went wrong. Undo erosion and uplift in the past viewIllustrative: erosion destroys the shapes it removes, so it can't be run backwards. Rock is added back at the rate the calibrated model erodes it today and uplift taken off, smoothed, for up to 2 million years.

Forces

A starting point; every setting below stays yours to change.

Rainfall

Rock map Measured against erosion rates worldwide, rock types differ by less than ×2 in how fast rivers cut them, and their hillslopes stand equally steep. Layered rock alternates hard and soft beds weakly. Loose sediment builds fans where rivers lose gradient.

Overall rock hardness

Sea level shift

Ice-age cyclesSea level drops up to 120 m and the snowline up to 1,100 m at a glacial maximum.

More forces research controls: snowline, orographic rain, climate drift, CO₂, glaciers, sediment, edges

Calibrated hardnessErodibility fitted to measured erosion rates (¹⁰Be) in 120 San Gabriel basins, for this cell size. Granite and gneiss erode 2.6–5.7× faster than at the default hardness (more on finer grids). On by default for maps centred in the San Gabriels.

Soil creep Rounds ridges and fills hollows.

Snowline adjustment Set from local climate when the terrain loads.

Rain shaped by the terrainMoist wind rising over the mountains rains on the windward side and dries out in the lee (Smith & Barstad's model), with the wind during rain at this spot. The map's total rain stays the same.

Terrain effect

Climate driftThe climate changes slowly as the plate carries the map to other latitudes, plus any extra trend you set, so long runs don't settle into a steady state. Plate moves the map's latitudeThe snowline follows the latitude the map's plate carries it to, at the plate's present motion (NNR-MORVEL56).

Extra snowline trend

Extra rainfall trend

Driven by

CO₂ from today

Summer sunshine at 65°N from Earth's orbit (La2004) sets when ice sheets grow and melt (Paillard's 1998 model).

GlaciersIce builds above the snowline, flows downhill, carves U-shaped valleys and fjords, and leaves moraines. SedimentEroded rock fills lakes, spreads over floodplains and fans, and builds deltas. With ice ages, valleys fill and re-cut into terraces. Rivers from outsideRivers that drain land beyond the map bring their water and sediment in at the edge.

Outside erosion How fast the land beyond the map wears down, which sets how much sediment those rivers carry.

Open map edgesThe map's edge rises and falls with the land just inside it (with a gentle 1% outlet slope) instead of staying at today's height, so long runs don't build cliffs against the edge. Off by default: fixed edges hold a basin's outlet at today's height, as a river leaving it through a gap does, and the basin fills with sediment instead of sinking with its outlet.

Tectonics

Uplift pattern Active faults near the pin load with the terrain.

Rock uplift The same everywhere.

Paint

More tectonics research controls: fault slip, earthquakes, plate motion, isostasy

Fault slipEach fault lifts one side and drops the other at its slip rate; landslides wear the step into a scarp. Soft fault edgesSpreads each fault's uplift over about 2 km, like the fold or shear zone at a real fault, instead of a step in one cell. On by default at San Gabriel and Milford Sound, where it brings runs from the past closer to today. EarthquakesFaults slip in jumps of about 4 m instead of steadily (visible at short step sizes). Fault activity changesFaults take turns: each is active (at twice its mapped rate) or idle for spells of about the timescale below, so the long-term average is the mapped rate. Thrust fronts step outward while active.

Activity timescale Average length of an active or idle spell.

Plate motion The far side of a strike-slip fault slides past along it, offsetting channels that cross it.

Carry faults with the plateFaults on the sliding side travel with it (in 2 km jumps), and faults from up to 150 km upstream slide into the map. The plate-boundary fault stays put. Real terrain from upstreamGround sliding in at the upstream edge is the real landscape beyond the map (up to 150 km of it), instead of what left at the far edge. Once it runs out the lanes wrap again. IsostasyThe crust floats on the mantle: erosion lets it rise, ice, sediment and the sea press it down.

Plate stiffness (Te) Elastic thickness of the lithosphere. 0 = every column floats on its own; stiffer plates spread the response over ~100 km.

View

Vertical exaggeration

Analysis

Readout

Uncertainty bandReruns the start 24 times with the erodibility varied by its calibration uncertainty (±25%, 1 sd) and shows the 10–90% range under mean ground change and rock eroded. Needs the GPU.

Highest point: —
Relief: —
Mean ground change: —
Rock eroded: —
Sediment stored: —
Brought in by rivers: —
Ice cover: —
Isostatic rebound: —
Plate offset: —
Latitude: —
Snowline: —
Rainfall: —
Sea level: —
Grid cell: —
Sim speed: —
Engine: —

Erosion amounts depend on grid size; compare runs on the same grid.

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Today

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