Open Questions: Deep Structure of the Earth

What heats the earth's core?: Brief discussion of the four sources of heat inside the Earth. Most of it is the result of radioactive decay.
Earth's Mantle: A ScienceWeek "symposium" consisting of excerpts and summaries of articles from various sources.
The Inside Story: September 1996 Scientific American In Depth article, subtitled "Detailed computer simulations help scientists delve into the Earth's interior."
Earth's Interior: Nice, very well-illustrated overview of the interior structure of the Earth, by the Nevada Seismological Laboratory.
Theorists tackle the Earth's core: October 1999 news article from Physics Web. "Geophysicists need to know the temperature at which iron melts at very high pressures in order to understand the structure of the Earth. Both the solid inner core and the molten outer core, which extend to 55% of the Earth's radius, consist mainly of iron. A group of theoretical physicists from the UK has now calculated the melting curve of iron from first principles."

Many questions of geophysics, such as the nature of convection cyles in the mantle, are difficult because of their relative inaccessibility to observation. A number of these questions are tied to the nature of the core-mantle boundary 3000 km. below the surface of the Earth.
The Mid-Cretaceous Superplume Episode
Roger L. Larson
Scientific American, February 1995, pp. 82-86: Superplumes are enormous upwellings of hot magma beginning at the base of the Earth's mantle and rising to the bottom of the lithosphere. The mid-Cretaceous event of 120 million years ago resulted in intense volcanic activity in the western Pacific seafloor.
Studies of the Earth's Deep Interior: Goals and Trends
Thorne Lay; Thomas J. Ahrens; Peter Olson; Joseph Smyth; David Looper
Physics Today, October 1990, pp. 44-52: Two convective engines are at work in the Earth's interior, driven by thermal and chemical processes. The engines are coupled to each other at the core-mantle boundary, 2900 km below the surface of the Earth.