Iceland lies astride the Mid-Atlantic Ridge with a belt of geologically active fissures and volcanoes running through the island. The centre of this belt corresponds to the meeting point of the American and European tectonic plates which move apart at an average rate of 10 cm a year. As a result of these features areas of geothermal heat abound in Iceland. There are two types of these areas: low-temperature and high-termperature. Around 250 low-temperature geothermal areas can be found outside of the active fissue zone. The temperature in these areas is generally below 150 C at a depth of 1000 metres. High-temperature geothermal areas are found only at active volcanic belts where the temperature of the water is not less than 200 C at a depth of 1000 metres. Geothermal energy is exploited in numerous ways. Today, more than 85% of Iceland's inhabitants enjoy domestic heating derived from geothermal energy. Horticultural greenhouses utilize this energy and in some areas electricity is produced by small geothermal power stations.