7. Geophysical Deductions from Observations of Heat Flow

  1. William H. K. Lee
  1. Gordon J. F. Macdonald

Published Online: 18 MAR 2013

DOI: 10.1029/GM008p0191

Terrestrial Heat Flow

Terrestrial Heat Flow

How to Cite

Macdonald, G. J. F. (1965) Geophysical Deductions from Observations of Heat Flow, in Terrestrial Heat Flow (ed W. H. K. Lee), American Geophysical Union, Washington, D.C.. doi: 10.1029/GM008p0191

Author Information

  1. Institute of Geophysics and Planetary Physics, University Of California, Los Angeles

Publication History

  1. Published Online: 18 MAR 2013
  2. Published Print: 1 JAN 1965

ISBN Information

Print ISBN: 9780875900087

Online ISBN: 9781118668825

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Keywords:

  • Chondritic Earth model;
  • Geophysical deductions;
  • Radioactive isotopes;
  • Surface heat flows;
  • Thermal conduction;
  • Thermal inertia of the Earth

Summary

It is well known that the Earth's surface heat flow is in approximate balance with the heat production in an Earth of chondritic composition. The ratio of K/U in crustal rocks, peridotite, dunite, and eclogite is about 1×104, in contrast to the ratio in chondrites of about 7.5×104. Numerical calculations demonstrate that Earth models which have uranium concentration 3 to 4 times that observed in meteorites and with K/U = 104 yield the observed heat flow. The computations clearly show that the present heat flow implies melting at depth unless either the thermal conductivity increases substantially with depth or radioactivity is concentrated at depths less than 300 to 400 km.

The general features of temperature-depth curves are similar for many models in which the energy is transmitted by radiation as well as by ordinary lattice conduction. The gradient of temperature is high near the surface but decreases within the Earth as the effective conductivity increases with increasing temperature. The temperature distribution depends sensitively on the parameters chosen. The computations do not attempt to account for the initial temperature gradient, nor are nonradioactive heat sources included.