This terminal moraine/end moraine was formed about 12000 years ago at the end of the Last Icetime. The strait between the peninsula and the nearest shore is very shallow, only a few meters deep.
Nice shot. I love glacial features. They are like ancient Roman ruins, partially obscured by vegetation. My home is 1/4 mile south of the Itasca moraine in Northern Minnesota, which rises about 180 feet above the lake elevation. Totally covered with red and white pines, the moraine from below is an east-west ridge that continues for many tens of miles to the eastern edge of the Wadena Outwash Plain left from the flood of a glacial lake when an ice plug broke free 12,000 years ago on Lake Agassiz. The Itasca Moraine from the ground is not dramatic as your beautiful scene.