Modern Lake Arthur is a smaller, man-made re-creation of glacial Lake Watts. Its normal water level is only 1,190 ft, and it is about six miles shorter than the old glacial lake. However, the new dam is near where the ice dam blocked Muddy Creek.
Near the middle of glacial Lake Watts, and miles from the gravel released from the glacier dam by melting, only silts and clays settled to the lake bottom. At the PA Route 528 bridge , ninety feet of water saturated, soft silt and clay (J) were not able to support the bridge, and it had to be redesigned. Although Lake Watts stood 70 ft higher than modern Lake Arthur, no high-level wave cut notches or beaches are visible, suggesting that Lake Watts was short-lived and had only small wave action.
As the glacier approached the western end of Lake Watts, coarser gravel (K) was deposited on top of the silts and clays that had been deposited.
When Moraine State Park was developed, the old, depleted oil and gas wells were plugged, strip mines backfilled, and deep mines sealed. However, a few traces of the drilling and mining can still be seen.
Along the Pleasant Valley Day-Use Area road, past the swimming beach (at the site marker), a strip mine highwall shows the sandstones and shales of the Kittanning Formation. This is the same unit that forms the Cleland Rock overlook (Site 6).
Kittanning coals were also strip and deep mined on the north shore of Lake Arthur. Evidence of this mining can be seen along the bike trail between mile 7 and the trail end (M). Look for sandstone blocks, rusty seeps from pits and small waste piles on the north side of the trail.