local stone and earth to enclose the structure. In North America, almost every native American group used earth sheltered structures to some extent. These structures have been called 'earth lodges' (see also: Barabara). When Europeans colonized North America, sod houses ("soddies") were common on the Great Plains. In China, man-made cave dwellings have been used as a shelter since 2,000 BC. In certain areas of northern China, like the provinces of Shaanxi and Shanxi, since the loess earth is structurally uniform and compacted, providing easy access to good quality building material with stable structure, earth-sheltered homes have been in use for centuries. 1970s–1980s Heyday The 1973 Oil Crisis saw the price of oil dramatically increase, which influenced vast social, economic and political changes worldwide. Combined with growing interest in alternative lifestyles and the back-to-the-land movement, the public of the US and elsewhere were becoming more interested in saving energy and protecting the environment. As early as the 1960s in the US, some innovators were designing contemporary earth shelters. After the oil crisis and until the early 1980s there was a new resurgence in interest earth shelter/underground home construction, which has been termed the first wave of earth covered dwellings. Architect Arthur Quarmby finished an earth sheltered building in Holme, England in 1975. Named "Underhill," It is recorded in the Guinness World Records as the "first underground house" in the UK. The majority of publications about earth sheltering date to this period, with dozens of books dedicated to the topic being published in the years leading up to 1983. The first International Conference on Earth-Sheltered Buildings was hosted in Sydney, Australia in 1983. A second conference was planned for 1986 in Minneapolis, USA. Other notable proponents of earth sheltering active in this era include Mike Oehler, Rob Roy, John Hait, Malcolm Wells, Peter Vetsch, Ken Kern and others. Modern times In the last 30 years earth sheltered homes have become increasingly popular. The technique is more common in Russia, China and Japan. It is possible that Northern China has more earth shelters than any other region. It is estimated that approximately 10 million people live in underground homes in the region. Some claim that thousands of people live underground in Europe and America. Notable European examples are the "Earth Houses" of Swiss architect Peter Vetsch. There are about 50 such earth shelters in Switzerland, including a residential estate of nine earth