Thomas Jaggar, American volcanologist (died 1953)

Thomas Augustus Jaggar Jr. was an American volcanologist. He founded the Hawaiian Volcano Observatory and directed it from 1912 to 1940. The son of Thomas Augustus Jaggar, Jaggar Jr. graduated with a PhD in geology from Harvard University in 1897. In 1902, he was one of the scientists that the United States sent to investigate the volcanic disasters at La Soufrière volcano, St Vincent, and Mont Pelée, Martinique, which he credited with inspiring him to make a life's work out of geology. He became head of the department of geology at Massachusetts Institute of Technology in 1906.