|Abstract from DBPedia||
Permafrost is ground that continuously remains frozen for two or more years, located on land or under the ocean. Permafrost does not have to be the first layer that is on the ground. It can be an inch to over miles deep into the Earth's surface. Some of the most common permafrost locations are located in the Northern Hemisphere. Almost a quarter of the Northern Hemisphere is underlain by permafrost, including 85% of Alaska, Greenland, Canada and Siberia. It can also be located in the Southern Hemisphere, just on mountain tops. Permafrost frequently occurs in ground ice, but it also can be presented in non-porous bedrock. Permafrost is formed from ice holding all different sorts of soil, sand, and rock combination together.
永久凍土（えいきゅうとうど、英語: permafrost）とは、2年間以上にわたり継続して温度0℃以下をとる地盤のことである。この用語の定義の上では、氷の存在ではなく温度条件で考える。 英語では、永久凍土のことを permafrost と表記するが、permanently frozen ground（永久に凍った土壌）の省略語で1945年に S. W. MULLERによって使われた。