Cosmogenic nuclide

A nuclide produced when cosmic rays interact with atoms in the atmosphere or Earth’s surface. Cosmogenic nuclides can be radioactive or stable.

Cosmic-ray spallation: A nuclear reaction in which energetic particles fragment an atomic nucleus into lighter products. It produces many cosmogenic nuclides by breaking target nuclei in rocks and minerals.
Cosmogenic nuclide dating: A method for estimating how long a surface or material has been exposed to cosmic rays. Measured nuclide concentrations can reveal exposure durations and burial histories.
Nuclide: A species of atom defined by its numbers of protons and neutrons. Cosmogenic nuclides are distinguished by the nuclei formed in cosmic-ray reactions.
Carbon-14: A radioactive carbon isotope with a half-life of about 5,730 years, produced naturally by cosmic-ray interactions. Its atmospheric production supplies the isotope used in radiocarbon dating.
Cosmic-ray neutron: A neutron generated in a cascade of interactions initiated by cosmic rays. Neutrons drive important reactions that form cosmogenic nuclides near Earth’s surface.
Exposure dating: A dating method that estimates the time a surface has been exposed to a measurable process or environment. Cosmogenic nuclides provide a clock for when rocks became exposed at Earth’s surface.
Radioactive decay: The spontaneous transformation of an unstable atomic nucleus into another nucleus or particle configuration. Decay competes with production and sets the timescale of radioactive cosmogenic nuclides.
Beryllium-10: A radioactive beryllium isotope with a half-life of about 1.39 million years, produced by cosmic-ray interactions. It accumulates in quartz and supports exposure, erosion, and burial studies.
Muon: An elementary particle similar to an electron but much heavier, produced in cosmic-ray cascades. Muons penetrate farther into rock than most secondary cosmic-ray particles and produce nuclides at depth.
Erosion rate: The speed at which material is removed from a land surface over time. Nuclide concentrations in bedrock or sediment can quantify long-term erosion.

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