What is radiogenic heat in Earth's crust?

Radiogenic heat is the thermal energy produced inside Earth through the radioactive decay of unstable isotopes found within the mantle and crust. Alongside primordial heat, it constitutes the primary source of Earth's internal heat budget, driving geological processes like plate tectonics and volcanism. Major heat-producing nuclides responsible for this energy include potassium-40, uranium-238, uranium-235, and thorium-232.

What we know

• Radiogenic heat produced by the radioactive decay of isotopes in the mantle and crust accounts for roughly half of Earth's estimated 47 terawatts of internal heat flow. [2]
• The major heat-producing nuclides responsible for generating Earth's radioactive heat are potassium-40, uranium-238, uranium-235, and thorium-232. [5]
• Because short-lived radioactive nuclides were more abundant in the past, Earth's radiogenic heat production was roughly twice as high three billion years ago. [5]
• Radiogenic heat originates from the interior and works in combination with primordial heat, whereas solar radiation dominates Earth's surface energy budget. [2, 5]

Where to go next

• what caused itWhere does Earth's primordial heat come from?
• what followedHow does mantle convection shape tectonic plates?
• how it workedHow do scientists use radioactive isotopes for dating rocks?
• a case in pointWhat is the Mohorovičić discontinuity?
• whenHow much higher was Earth's heat production billions of years ago?
• an unexpected connectionHow does ancient radioactive decay explain rocks that can no longer form?Higher rates of radiogenic heat production billions of years ago drove massive mantle temperatures that allowed the formation of unique igneous rocks like komatiites, which no longer form today.

Sources

• [1]Earth's internal heat budget (Wikidata Q17009773) · CC0 1.0
• [2]Earth's internal heat budget · CC BY-SA 4.0
• [3]Radiogenic nuclide · CC BY-SA 4.0
• [4]Earth's crust · CC BY-SA 4.0
• [5]Geothermal gradient · CC BY-SA 4.0