The Madison Boulder is one of the largest known glacial erratics in North America and among the largest in the world; it is preserved in the 17-acre (6.9 ha) Madison Boulder Natural Area in Madison, New Hampshire. The boulder is a huge granite rock measuring 83 feet (25 m) in length, 23 feet (7.0 m) in height above the ground, and 37 feet (11 m) in width. It weighs upwards of 5,000 tons. A part of the block is buried, probably to a depth of ten to twelve feet. It was acquired by the state from the Kennett family In 1946. In 1970, Madison Boulder was designated as a National Natural Landmark by the National Park Service.
|Madison Boulder Natural Area|
|Location||Madison, New Hampshire, United States|
|Area||17 acres (6.9 ha)|
|Elevation||512 feet (156 m)|
|Administered by||New Hampshire Division of Parks and Recreation|
|Designation||National Natural Landmark|
|Website||Madison Boulder Natural Area|
- "Madison Boulder State Geologic Site". Geographic Names Information System. United States Geological Survey.
- "State Lands" (PDF). New Hampshire Department of Resources and Economic Development. July 2007. Retrieved September 19, 2020.
- Lisa Mausolf, Preservation Consultant (March 2019). "New Hampshire State Parks: Mid-Century Modern (1945-1975): Historic Context Study" (PDF). New Hampshire Division of Parks and Recreation. p. 24. Retrieved September 19, 2020.
- "Madison Boulder Natural Area". New Hampshire Division of Parks and Recreation. Retrieved September 19, 2020.
- "Madison Boulder". National Natural Landmarks. National Park Service. Retrieved September 19, 2020.
It illustrates the power of an ice sheet to move large blocks of fractured bedrock over substantial distances.
- Madison Boulder Natural Area New Hampshire Department of Natural and Cultural Resources