Chat Moss is a lowland raised bog. In areas where drainage is poor, water-logging can slow down plant decomposition, producing peat, which over the years can raise the level of the bog above that of the surrounding land. The moss occupies an area of about , and is about long, about across at its widest point, lying above sea level. Chat Moss lies mainly in Salford, but extends into Wigan. By the 1990s, an estimated 72 per cent of the bog had been reclaimed, most of it for agriculture. About of degraded bog remain, with of undamaged peat deposits in four former peat extraction sites. The peat varies in depth between and .