Robert P. Sharp (1911-2004) originated the Geology Underfoot series. In 1993 he took on Allen, 43 years his junior, to cowrite the first book in the series, Geology Underfoot in Southern California. Bob taught generations of geology students at the California Institute of Technology (Caltech), leading them on field trips across the West and Hawaii even into his 90s. A true polymath who could explain complex concepts to anyone, his specialty fields included sand dune physics, glaciology, and planetary sciences. He was among the first to interpret dune processes in orbital imagery from Mars and received the Penrose Medal from the Geological Society of America, its highest honor, in 1977. In further recognition of his contributions to diverse fields, a mountain and a glacier in Antartica, a Mars-crossing asteroid, and a mountain on Mars have been named in his honor.
