Complex sentence: Deposited more than 14,000 years ago by the Vashon Glacier, it was a landmark for Native Americans in what was once a dense forest; later it became a destination for picnickers, university students, climbers, and hippies.
Split into simpler sentences: Deposited more than 14,000 years ago by the Vashon Glacier, it was a landmark for Native Americans in what was once a dense forest. Later it became a destination for picnickers, university students, climbers, and hippies.