Heat Flow and Earth's Interior
Heat escaping from the Earth's interior powers convection, the geodynamo, and plate tectonics, and measuring this heat flow together with seismic and mineral-physics data reveals the composition, structure, and evolution of the deep planet.
Definition
Heat flow and Earth's interior is the study of the planet's internal thermal state and energy budget, integrating measured surface heat flow, seismic structure, and high-pressure mineral physics to determine the composition, temperature, and evolution of the crust, mantle, and core.
Scope
This area covers the Earth's thermal state and the constitution of its interior: terrestrial heat flow and its sources in radioactivity and primordial and core heat, the layered composition and structure of the crust, mantle, and core, and the mineral physics that connects laboratory measurements at high pressure and temperature to the deep Earth. It treats the geotherm, modes of heat transport, and the long-term thermal evolution of the planet. The emphasis is on the energy budget and physical state of the interior.
Sub-topics
Core questions
- How much heat flows out of the Earth, and where does it come from?
- What are the composition and physical structure of the crust, mantle, and core?
- How do high-pressure mineral experiments constrain the deep interior?
- How has the Earth's thermal state evolved over geological time?
Key concepts
- Terrestrial heat flow and the geotherm
- Radiogenic, primordial, and core heat sources
- Layered structure: crust, mantle, and core
- Mineral physics at high pressure and temperature
- Thermal evolution and cooling of the Earth
Key theories
- Earth's heat budget
- The global surface heat flow is supplied by radioactive decay of long-lived isotopes together with the slow release of primordial and core heat, and this budget sets the energy available to drive mantle convection, plate tectonics, and the geodynamo.
- Layered structure of the interior
- Seismology, gravity, and mineral physics together establish that the Earth is differentiated into a thin crust, a silicate mantle with phase-transition layering, and a metallic core with a liquid outer and solid inner part.
Clinical relevance
The Earth's internal heat drives the convection responsible for plate tectonics, volcanism, and the magnetic field, supports geothermal energy resources, and underpins models of how the planet and others have evolved and remained habitable.
History
Kelvin's nineteenth-century cooling estimate of the Earth's age, later overturned by the discovery of radioactivity, opened the study of terrestrial heat; twentieth-century seismology delineated the interior layers, Birch related seismic velocity to composition, and modern heat-flow compilations and mineral physics quantified the planet's energy budget.
Key figures
- William Thomson (Lord Kelvin)
- Inge Lehmann
- Francis Birch
- Edward Bullard
Related topics
Seminal works
- fowler2005
- turcotte2014
- stacey2008
Frequently asked questions
- Where does the Earth's internal heat come from?
- Most of it comes from the radioactive decay of long-lived isotopes such as uranium, thorium, and potassium, with a significant remainder being primordial heat left from the planet's formation and heat released as the core slowly cools and the inner core freezes.
- How do we know what the deep Earth is made of if we cannot sample it?
- Scientists combine seismic measurements of how waves travel through the interior with laboratory experiments that recreate the immense pressures and temperatures at depth, matching the observed properties to candidate minerals and metals to infer the interior's composition.