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The Life of the Peninsula: A Migrating Peninsula |
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Presque Isle is a recurving sand spit. Geologists believe it formed more than 11,000 years ago. Over time the coastline "floated" as the forces of wind and water carried sand from the neck of the peninsula eastward, depositing it at Gull Point and causing the Gull Point area to grow. This growth and migration of the peninsula occurred rapidly, at least in geologic time. Scientists believe that the peninsula has moved eastward one-half mile per century, although they see smaller changes every year. These changes created an extremely diverse and fragile environment. Because of its diversity, Presque Isle is a natural laboratory for viewing the geologic past and watching geologic forces in motion.
Presque Isle's location relates to a ridge of sediment called a moraine that crosses Lake Erie. Huge slowly moving glaciers carry moraines, consisting of clay, sand and gravel. The glacier that formed the moraine across Lake Erie was a late, minor advance of the last major ice sheet that covered much of northern Pennsylvania. About 13,000 to 14,000 years ago, the small glacier moved southward into the valley now occupied by Lake Erie. The moraine marks the location where the glacier stopped, and was left behind as the ice melted away.
Although the French name Presque Isle means "almost an island", the area has actually been a real island several times. Storm waves have broken through the neck to isolate the main section of the spit at least four times since 1819. One gap remained open for 32 years.
As westerly waves wash upon the beaches in a diagonal direction, sand and pebbles carried with them are left on the shore as the waves recede. Upon each wave's rush, they are deposited a little farther east, adding to Presque Isle's eastward growth. Gull Point has been growing for most of the 1900s and continues to do so today.
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PI Newsflash
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