Thermochronology

Thermochronology reconstructs rocks’ temperature histories from minerals whose isotopic systems respond predictably to heating and cooling. It constrains when rocks cooled through particular temperature ranges, rather than directly dating their formation.

Closure temperature: The approximate temperature below which a mineral’s isotopic system retains daughter products faster than they diffuse away. It links a measured thermochronologic age to the temperature a rock crossed during cooling.
Fission-track dating: A dating method that counts radiation-damage tracks in minerals, whose abundance changes through annealing. Track annealing makes its ages sensitive to temperature as well as elapsed time.
Exhumation: The process by which rocks move toward Earth’s surface as overlying material is removed or the crust deforms. Cooling ages commonly constrain when rocks were brought upward and exposed by erosion or tectonics.
Geochronology: The science of determining the ages and timing of geological materials and events. Thermochronology is a specialized branch that interprets ages through thermal behavior.
Inverse problem: A problem in which causes or model parameters are inferred from observed effects, often with multiple possible solutions. Different temperature paths can produce similar thermochronologic ages and track-length patterns.
Diffusion: The net movement of particles caused by random motion, often driven by concentration or chemical-potential gradients. Isotopic resetting depends on how quickly daughter products diffuse through minerals as temperature changes.
Uranium–thorium–helium dating: A dating method that measures helium produced by uranium and thorium decay and retained in minerals. Helium diffusion gives this system a strong response to low-temperature cooling.
Low-temperature thermochronology: Thermochronologic methods that track rocks’ passage through relatively cool conditions near Earth’s surface. It is used to reconstruct shallow burial, uplift, erosion, and landscape evolution.
Thermobarometry: The estimation of a rock’s formation or metamorphic pressure and temperature from mineral compositions. It estimates conditions recorded by mineral equilibria, unlike thermochronology’s reconstruction through time.
Thermal diffusivity: A material property describing how quickly temperature disturbances spread through a substance. Uncertain heat transport affects modeled rock temperatures and the histories inferred from them.

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