Gertrude is another small island just offshore of McNeil, this one on the north side at the mouth of Still Harbor. It's off limits to folks like us to protect the seals that haul out on the beaches - particularly at the south end. The east side is very sheltered, with salicornia growing on the beach and a low bank overhung with trees. The west side is a bit more exposed and there is more evidence of erosion.
The funky little spit at the south end appears to be a low terrace -- the flat surface is well above normal backshore elevations and consists of a low erosional scarp. Another geologic question goes unanswered!