Many of the corpses were decayed beyond identification. Lignite begins as an accumulation of partially decayed plant material, or peat. Following its destruction, the temple gradually decayed and collapsed. Without active care, many bridges have decayed or grown wild, becoming unusable. Flags that have decayed or faded should not be displayed. Due to the altitude, atmospheric drag decayed the orbit of most debris within a decade. Once overland, the cyclone rapidly decayed as convection dissipated. Some of the film stock had decayed badly. Much of the radioactivity had decayed by 1980. After his demise, Sri Lanka gradually decayed in power. With such short lifetimes, these soon decayed away to negligible amounts. One half of the site was decayed limestone while the other half was soft rock. This isotope has long decayed and is thus referred to as "extinct". By January 2014, 24% of the known debris had actually decayed. By the 1920s, many of the housing areas of Wycombe had decayed into slums.