Francis Birch

Albert Francis Birch, known as Francis Birch, was an American geophysicist, born in 1903 in Washington, D.C., and died in 1992 in Cambridge, Massachusetts. He is considered one of the founders of solid Earth geophysics, and in 1952 he demonstrated that Earth's mantle is composed chiefly of silicate minerals surrounding an inner and outer core of molten iron. His 1961 papers established a linear relationship between compressional wave velocity and rock density that became known as Birch's law, and he also developed the Birch-Murnaghan equation of state describing how materials compress under pressure.