which was brought about by the earlier price surge. During this period, the industry in the U.S. was characterized by a move towards low-sulfur coal.<ref>"Coal Mining Industry Report" IBISWorld, 2009</ref> In 1987 Wyoming became the largest coal producing state. It uses strip mining exclusively. Wyoming's coal reserves total about , or 14.2% of the U.S. coal reserve. In 2008, competition was intense in the US coal mining industry with some U.S. mines approaching the end of their useful life (mine closure). Other coal-producing countries also stepped up production to win a share of traditional US export markets. Coal is used primarily to generate electricity, but the rapid drop in natural gas prices after 2008 created severe competition. Other countries In the 21st century, Indonesia has expanded its coal mining and by 2011 ranked #5 globally in production. By 2011 Kazakhstan ranks in the top ten in terms of coal production and reserves. Lignite ("brown coal") remains important with Germany, China and Russia the largest producers. Disasters Mining has always been especially dangerous, because of explosions, roof cave-ins, and the difficulty of underground rescue. The worst single disaster in British coal mining history was at Senghenydd in the South Wales coalfield. On the morning of 14 October 1913 an explosion and subsequent fire killed 436 men and boys. Only 72 bodies were recovered. It followed a series of many extensive Mining accidents in the late 19th century, such as The Oaks explosion of 1866 and the Hartley Colliery Disaster of 1862. Most of the explosions were caused by firedamp ignitions followed by coal dust explosions. At Hartley there was no explosion, but the miners entombed when the single shaft was blocked by a broken cast iron beam from the haulage engine. Deaths were mainly caused by carbon monoxide poisoning, known as afterdamp. Mitsubishi Hojyo coal mine disaster, occurred on 15 December 1914 at the Mitsubishi Hojyo coal mine located in the Kyushu Island of Japan. The disaster directly led to the deaths of 687, representing the worst mining incident in Japanese history. The Courrières mine disaster, Europe's worst mining accident, caused the death of 1,099 miners in Northern France on 10 March 1906. The Benxihu Colliery accident in China on April 26, 1942, killed 1,549 miners. As well as disasters directly affecting mines, there have been disasters attributable to the impact of mining on the surrounding landscapes and communities. The Aberfan