Birch, Francis

Birch, (Albert) Francis (1903–  ) geophysicist; born in Washington, D.C. His studies of elasticity of rocks and minerals at high pressures and temperatures contributed extensively to knowledge of the composition of the earth. His proposal (1940) that the earth's innermost core is not liquid, but consists mainly of solid crystalline iron, was confirmed in 1971. Birch became emeritus professor of geology at Harvard University (1974).