 In the months after the eruption, the crater floor of St. Helens remained hot and unstable, with five minor volcanic eruptions, and lava dome construction between May and October 1980. After the eruptions ceased in the winter of 1980, the crater floor cooled down enough for snow and ice accumulation. Beginning with snowfall in the winter of 1980-1981, the glacier began to grow very rapidly in the shadow of the crater. The glacier thickened at a rate of as high as 50 ft (15 m) per year and advanced northward as much as 135 ft (41 m) a year. This glacier growth was discovered by scientists working in the crater about seven to nine years later. However, the existence of the glacier was not publicized until 1999. By 2004, Crater Glacier covered about 0.36 square mile (0.93 km2), about 20 % of the glacier area in the pre-1980 glaciers, and there was a western and eastern lobe flowing around the 1980s dome. Due to the gas emissions on the crater floor, there were glacier caves (ice caves) in the once smooth glacial ice, and several of them had been explored by the late 1990s.
