Mansel Island, 112 km long by 48 km wide, is the smallest of 3 islands lying across the entrance to HUDSON BAY. Its topography features a gently undulating limestone lowland with elevations not exceeding 100 m. The entire island was submerged under higher sea levels at the end of the last glaciation. A legacy of this marine transgression is the particularly striking relic beach deposits and elevated former shoreline features. The island itself is an outcrop of ancient resistant marine sediments and is part of an elongated escarpment extending 725 km along the north and east margin of Hudson Bay.