Geochronology works out when things happened in Earth's history — volcanic eruptions, the rise of mountains, the formation of mineral deposits, changes in the landscape. Those dates underpin geologic mapping and inform decisions on hazard mitigation, natural resource management and resilient infrastructure.
The USGS Geochron database makes more than 300,000 published, public age measurements from more than 40,000 geologic samples available to anyone. Built with state geological surveys and geoscientists around the world, it is the most comprehensive collection of geochronological data for the United States.
Why it pays
- No duplicate work: open access to dates for more than 40,000 samples saves costly repeat measurements and speeds research in federal agencies, state surveys, universities and industry.
- Critical minerals: it supports efforts to secure domestic supplies of minerals essential for energy technology, national defense and advanced manufacturing, reducing dependence on foreign sources.
- Hazards: more accurate, timely risk evaluations help protect lives and infrastructure.
- More from public money: removing barriers to essential geologic data multiplies the return on public investment in earth science.
How geologists date rocks
Some rock-forming minerals contain small amounts of radioactive isotopes that slowly change from one form, the parent isotope, into another, the daughter isotope, at a steady, known rate — a natural clock.
- While a rock is hot, daughter isotopes can escape from the mineral and are lost.
- The clock starts when the rock cools below a critical temperature — for example, when erupted lava cools — and its minerals begin to seal the daughter isotopes in.
- Measuring the isotopes in a rock today shows how long ago that happened. Different isotopes reveal different processes and systems.
Radioactive decay as an hourglass: (A) in an open system, daughter isotopes escape and cannot measure time; (B) once the system closes, they accumulate, starting the clock geochronologists read. Graphic: U.S. Geological Survey.
What the dates are used for
| Use | How ages help |
|---|---|
| Mineral and energy resources | the timing of petroleum systems and mineral deposits points to exploration targets and helps assess supplies of critical minerals |
| Natural hazards | dating past eruptions, landslides and earthquakes improves estimates of the chances and consequences of future ones |
| Geologic mapping | accurate maps for land-use planning, infrastructure and resource management depend on knowing when rocks and features formed |
| Earth history | precise ages trace the evolution of life, rebuild ancient plate movements and test explanations for events such as mass extinctions |
How dating methods apply across tectonic settings, and where mineral resources, energy resources and natural hazards occur. Methods shown: argon-argon, luminescence (OSL), rhenium-osmium, uranium-lead and uranium-series disequilibrium. Graphic: U.S. Geological Survey.
Using the database
- Interactive map explorer: browse and filter samples by location, age and method.
- Complete dataset: download everything, with metadata and a data dictionary.
- GIS services: connect directly through web-hosted feature services.
Contributing data
The project accepts published geochronology and thermochronology data from government agencies, universities and industry. Each sample needs an identifier, age, location and citation. Templates and a user guide are at doi.org/10.5066/P14SSWBH; the project team reviews submissions and adds them to the database regularly.
Sources
Based on "USGS Geochron Database," U.S. Geological Survey Fact Sheet 2026–3016, U.S. Geological Survey; a work of the United States government in the public domain. Its two graphics are reproduced from the fact sheet; its screenshot of the map explorer is not.
Licence: CC0 1.0 (public domain) · Adapted from pubs.usgs.gov
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