Joseph BarrellBorn 15 Dec 1869; died 4 May 1919 at age 49. American geologist who extended ideas on sedimentary rocks made by marine sedimentation to modification by the action of rivers, winds, and ice. He proposed (1916) that the bright red colour of many Devonian rocks indicated an arid climate that baked them dry, like bricks. He suggested droughts caused lung-fish to evolve into air-breathing land vertebrates, including tetrapods. He applied the new science of radioactive dating in 1917 to recalculate Earth's age to a few billion years, at a time when many geologists still preferred an age of 100 million years. He also emphasized that geological processes vary in intensity in a cyclical rather than a uniform fashion, so current rates of geological change used in prior estimates were not reliable guides.« |
