When the ice that covered this land slowly melted, it dropped in its tracks great accumulations of gravel and rocks. Boulders transported and deposited by glaciers are called "erratics." Erratics are rounded and noticeably different in composition from local bedrock.
Glaciers carry huge loads of rock. The rocks come to rest where the melting ice crops them. The large boulder perched above on the South Bubble is a striking example.
20,000 years ago
Before the ice sheet came, the rugged Acadian highland was a granite ridge running east-west.
17,000 years ago
Huge tongues of ice invaded the valleys on the north slopes, cut through the passes, and engulfed the mountains on their way to the sea.
15,000 years ago
At its maximum the ice covered Acadia with a sheet over 8,000 feet (2400m) thick! The sheet extended about 200 miles (320km) seaward to the edge of the continental shelf.
13,500 years ago
Climatic warming caused the ice to melt back to the north. Ocean waters rose, flooding the foothills of the mountains.
10,000 years ago to present
The ice changed the shape of Acadia. It cut deep U-shaped valleys running north-south, and rounded and polished the mountaintops.