of the steam beneath the surface exceeds the pressure exerted by the weight of the overlying ground. This results in an explosion. A mixture of hot water, steam, hot mud and pumice is ejected into the air. Material may be blown up to 100 m, leaving behind holes or craters as deep as 20 m. Hydrothermal eruptions occur about once a year. Fumaroles The openings in the earth surface, where geothermal steam and gases are emitted, are called fumaroles. These vary in size from one centimetre to half a meter in diameter. The most powerful fumarole observed at Craters of the Moon occurred December 1967. It had a heat output of 116 MW. Mudpool Currently, only one of the craters has a mudpool. Here the gases (mainly H2S) react with water to form sulphuric acid. This reacts with the rocks, turning it to clay. When there is water present, this forms the grey coloured mudpools “that bubble and burp as steam and gas escape through them”. Vegetation Much of the ground at Craters of the Moon is warm or hot. This of course affects the vegetation. Only few species can survive. One is the prostrate kanuka, a variety of kanuka (Kunzea ericoides var. microflora). Other species include ferns and mosses that usually grow only in the tropics or warmer frost-free climates. Visitor access to Craters of the Moon Craters of the Moon is open to visitors all year round. The area is easily reached by car from Taupo, being on the end of Karapiti Road, that branches off State Highway 1/5, 4 km north of Taupo. There is a carpark, and an information kiosk at the entrance. An entrance fee applies. Visitors can walk a main track circuit, suited for people of all ages and fitness levels, which is also wheelchair accessible. This loop takes 45 minutes to walk. A steeper loop, taking an additional 20 minutes, climbs to a viewing point. Due to the somewhat poisonous fumes and the fact that ground temperatures around steam vents can reach dangerous levels, the paths and board walkways that allow access to the field are relaid at irregular intervals to bypass them. Craters of the Moon Trust In 1991 the constant break-ins in cars at the rather isolated car park caused local solicitor Jeremy Nash to seek volunteers to maintain passive security. In that same year a first kiosk was built near