He is perhaps best known for his work on the staff of Stephen Long's expedition to the Great Lakes in 1823, an account of which he published in 1824.[4] In the account he first hypothesized the existence of what is now known as Lake Agassiz. Formed at the end of the last ice age during the retreat of the great North American glaciers Lake Agassiz was, at its peak, much larger than any currently existing lake. The tremendous significance of the discovery has come to be appreciated in recent decades because the draining of Lake Agassiz into the North Atlantic Ocean is now generally thought to have been responsible for sudden periods of cooling of Northern Hemisphere climate at the end of the Pleistocene. The most dramatic of these periods of cooling is known as the Younger Dryas.
^John Keating and his forbears (1918) Author: Keating, John Percy, 1855-1920. Reprinted from the Records of the American Catholic Historical Society Vol. XXIX No. 4 December 1918. Identifier-ark: ark:/13960/t6f19440p https://archive.org/details/johnkeatinghisfo00keat The author was a great-grandson of John. Accessed 14 July 2011
