# A rock in the creek turned out to be a mastodon molar

> A geologist doing routine field surveys in San Mateo County picked up what looked like a weird rock. It was an Ice Age tooth.
- Title: A rock in the creek turned out to be a mastodon molar
- Summary: A geologist doing routine field surveys in San Mateo County picked up what looked like a weird rock. It was an Ice Age tooth. Field surveys for an ordinary…
- Keywords: fossils, paleontology, bay area, ice age, mastodon, news, local, rock, creek, turned, molar, ABC7 New York
- Source: ABC7 New York — https://abc7ny.com/story/10000-year-old-fossilized-mastodon-tooth-found-san-mateo-county-california-creek/19820069
- Published: 2026-09-11T17:06:50+00:00
- Read time: 1 min
- Topics: fossils, paleontology, bay area, ice age, mastodon, news, local
## An Ice Age tooth in a creek
A fossilized Pacific mastodon tooth, at least 10,000 years old, turned up in a creek bed in a Midpeninsula Regional Open Space District preserve in San Mateo County.
## Found during routine survey work
Nobody was hunting fossils. The tooth surfaced during field surveys for a habitat enhancement project, and geologist Brigid Lynch was the one who spotted it.

> As a geologist, I've gone out and seen stuff in the field, but definitely nothing as exciting as this
## Mistaken for an odd rock
It was written off as a strangely shaped rock until paleontologists confirmed it was an intact molar from an adult Pacific mastodon.
## The best one anyone has seen
The molar measures about 8.5 inches long, 7 inches deep and 3 inches wide, and arrived in what officials called immaculate condition.

> It's the most complete mastodon molar from our area, and the most spectacular mastodon molar that I've ever seen
## Not a mammoth, not quite
Pacific mastodons roamed California, Oregon, the northern Rockies and parts of Mexico until 11,700 years ago. Narrower teeth, thicker leg bones, different tusks, and molars built to crush twigs.
## Next stop, Stanford
Researchers at the Doerr School of Sustainability will carbon date the tooth and make a 3D scan, adding to work showing mastodons migrated long distances as the climate shifted.

> We can study fossils to better understand Earth's past, past wildlife and the ecosystem they were a part of
## Key takeaway

Field surveys for an ordinary habitat project turned up the most complete Pacific mastodon molar ever found in the Bay Area, and Stanford will now date and scan it.