A spore drifts
Each colonist begins as a particle released near the crust, taking a random walk across the granite — no destination, no gradient, just Brownian drift over the rock face.
/ˈʌsniːə/·saxicolous·slow colonists
Usnea saxatilis, on granite — a crust that keeps the time.
We build instruments that read time off things that grow.
A lichen is a clock that runs in millimetres per century. USNEA seeds the rock and lets diffusion do the drawing — every crust on this page is a real aggregation, assembled one wandering spore at a time.
Crust coverage
0.0%
Colonists fixed
0
Simulated age
0 yr
Growth rate
0.0 /s
The boulder is colonising as you read. Click any bare granite to seed a spore.
01 — Substrate
Granite gives nothing away.
Bare rock is the hardest address in botany — no soil, no shelter, wind and frost and a century of nothing. Saxicolous lichens live there anyway. A spore lands in a fracture, a fungus and an alga strike a bargain, and a thallus begins to spread outward across the stone at roughly the pace a fingernail grows, then slower. USNEA reads those crusts as dials: measure the diameter, know the decade.
0.4 mm/yr
Radial spread of a settled granite crust, and it decelerates.
120 yr
To close a crust the size of a clenched fist.
−9 °C
Still metabolising. Lichens do not read the weather.
1 particle
The whole crust assembles this way — one at a time.
02 — How a crust spreads
Wander. Touch. Fix.
The growth on this page is diffusion-limited aggregation. It is not a timelapse and not a texture — it is the actual rule that builds coral, frost and mineral dendrites, run live in the margin.
It finds an edge
The walk continues until the drifting particle grazes a cell already colonised. Interiors fill slowly; the exposed growing edge catches wanderers first, so the crust reaches outward in fingers.
And it stays
On contact it fixes — permanently, part of the crust, a new edge for the next wanderer to find. Sulphur marks the fresh growth; the body behind it settles to sage as it ages.
03 — The slow clock
Decades, compressed to a minute.
0yr
Simulated age of boulder GR‑14, inferred from crust diameter. It advances as the aggregation fills — quickly at first, then geologically.
Colonists fixed
0
Crust coverage
0.0%
Growth rate
0.0 particles/s
No timelapse. The aggregation above is computed on this page — a random walk that only fixes where it touches. Reload and it grows a different crust; the rule is fixed, the outcome never is.
04 — Field notes
The survey book, unabridged.
1994‑03‑02
First flagged GR‑14 above the Serpentine cascade. A single crust, 31 mm across, sulphur margin still bright. Estimated seed date: 1917.
2009‑11‑18
Re‑measured. 37 mm — six millimetres in fifteen years, exactly on the granite curve. The boulder keeps better time than the tide gauge downstream.
2021‑06‑07
Two crusts have met and fused along a quartz vein. Where they touched, growth stopped dead: no edge left to wander to. A crust needs an outside to keep spreading.
2026‑07‑09
Re‑seeded the simulation from this survey. The rule that draws the page is the rule on the rock. Slower, out there, by a factor of about four million.
05 — Commission
Put a slow system to work.
USNEA models colonisation, spread and settling for anyone who needs to see a process that outlasts a meeting — deep-time exhibits, land-restoration forecasts, instruments that turn growth into a reading. We work from Perth, in granite, at the pace of the thing itself.
USNEA Field Studio · Lichenometry & slow systems · Darlington, Western Australia · Est. by patience