Ground Truth · live core sample · every layer cited
The Ground Beneath You
Name any place on Earth and drill a core straight down through it. Each
layer is a real rock unit recorded beneath that point — its age, its stone, and the fossils
found near it — pulled live from open geological databases. Then trace where that exact ground
sat : a deep-time journey across the latitudes, reconstructed from the plate-tectonic record.
The deep column runs richest across North America; elsewhere you'll strike the surface rock and its age.
Nothing here is generated, and where the ground isn't mapped, it says so.
Name a place, or use a starting point below.
the ground remembers · the collective map
Anyone who drills a core here can leave a mark — a wordless,
nameless record that someone drilled here . This map is every mark ever left, on this
page and on the sibling sky page , drawn live from
the shared archive. A mark stores a 0.1° cell, a kind, and a count — nothing else, and
nothing about you.
reading the archive…
✛ Leave a mark — someone drilled here
stores the 0.1° cell (~11 km), the kind, a count — no name, no exact point, no trace of you
The one rule: it can never lie about anything real.
Where your query goes. The place name you type, and the point you drill, are sent to this site and nowhere else. Our own worker asks the databases above on the page's behalf, so they receive the request from us and never from you: not your address, not your browser, not this page as a referrer. The worker keeps the answer in a cache and stores nothing about what was asked, and the only thing it counts is a per-day total against a salted hash of your address, which is the same thing the rest of this site already does and knows nothing about your query. This is a real improvement and not a disappearance: you are trusting us instead of trusting four strangers, and the check for it is research/atlas-proxy/verify-atlas-proxy.mjs , which fails if any part of a query ever reaches storage or if a page ever addresses an outside host directly. Before 2026-08-09 these lookups went straight from your browser to the databases.
Rock column from Macrostrat ,
a community geological database. Fossils from the
Paleobiology Database .
Place lookup via OpenStreetMap / Nominatim .
The deep-time journey — where the ground sat as each layer formed — is reconstructed live by the
GPlates Web Service (EarthByte),
driven by the MERDITH2021
billion-year full-plate model (Merdith et al. 2021, Earth-Science Reviews 214, 103477) and
cross-checked against the MATTHEWS2016 and PALEOMAP models. Paleolatitude is anchored
by the remanent magnetism frozen into old rock and agrees closely across models; paleolongitude
is poorly constrained and differs between them, so the journey reports latitude and the latitudinal zone, not an
east–west position. The point is carried back on its present tectonic plate — meaningful for old continental
crust, not for ground younger than the age shown — and this is a position, not a climate.
Geologic period names are mapped from each unit's numeric age (ICS time scale); ages, rock
types, formation names, and fossils are reported exactly as the databases return them.
Macrostrat's deep stratigraphic columns are densest across North America; for other
places the page shows the near-surface units from regional and global geologic maps ,
which is why some cores run deep and others stop near the top. The column is the published
stratigraphy for an area — read it as the ground's order and age, not a promise that one
borehole here would strike every layer. Unconformities — long gaps where rock was never laid
down, or was eroded away — are shown as gaps, because that missing time is genuinely there.
The marks. The map above is this page's collective layer: anyone who
drills can leave a wordless mark, and the map is every mark ever left — here and on
the sibling sky page , which shares the same archive.
One mark's entire record is a 0.1° cell (~11 km), a kind (drilled / looked up), and a
count; the exact point is quantized away before storage, and no name, address, or
fingerprint of any sort is kept, so a mark cannot be traced to anyone. There is deliberately
no text field — a map with no words can't lie in words, and needs no moderator. The archive is
public: /api/marks returns every cell, and the machinery — validation,
quantization, rate limits, the storage shape — is locked in
research/the-marks/verify.mjs (43 offline checks against the same code that
serves this page). Land outline from
Natural Earth
(public domain), regenerable by research/the-marks/build-world-outline.mjs.