Map of ancient Lake Agassiz (1896)

This map was published by Warren Upham in 1896, in monograph number 25 of the United States Geological Survey, devoted entirely to Lake Agassiz.

Upham's map is the first representation of the vast expanse of this ancient periglacial lake. Upham devoted several years of his life to conducting the first comprehensive study of all the geological formations linked to Lake Agassiz, which was published in 1890 in Canada and six years later in the monograph of the United States Geological Survey.

Lake Agassiz was formed when the Laurentian ice sheet, which covered much of North America during the Ice Age, receded. Between 12,000 BC and 8,000 BC, this lake covered an area of more than 440,000 km², larger than the current area of the Caspian Sea.

Currently, it is believed that Upham's map underestimates the actual size that Lake Agassiz reached.

Sources

• The glacial lake Agassiz
• Map showing the areas of Lake Agassiz and the Upper Laurentian Lakes (1895)