nited States of America (often shortened to the United States, USA, U.S. or colloquially America) is a country of the western hemisphere, comprising fifty states and numerous territories. Forty-eight contiguous states lie in central North America between the Pacific and Atlantic Oceans, bound on land by Canada to the north and Mexico to the south; Alaska is in the northwest of the continent with Canada to its east, and Hawaii is in the mid-Pacific. The United States is a federal constitutional republic; Washington, its capital, is coextensive with the District of Columbia (D.C.), the federal capital district.

Grand Canyon National Park

Carved out by the Colorado river, the Grand Canyon (nearly 1,500 m deep) is the most spectacular gorge in the world. Located in the state of Arizona, it cuts across the Grand Canyon National Park. Its horizontal strata retrace the geological history of the past 2 billion years. There are also prehistoric traces of human adaptation to a particularly harsh environment.

Ilulissat Icefjord

Located on the west coast of Greenland, 250-km north of the Arctic Circle, Greenlandâ^Ts Ilulissat Icefjord (40,240-ha) is the sea mouth of Sermeq Kujalleq, one of the few glaciers through which the Greenland ice cap reaches the sea. Sermeq Kujalleq is one of the fastest (19-m per day) and most active glaciers in the world. Its annual calving of over 35 cubic kilometres of ice, i.e. 10% of the production of all Greenland calf ice and more than any other glacier outside Antarctica. Studied for over 250 years, it has helped develop our understanding of climate change and icecap glaciology. The combination of a huge ice-sheet and the dramatic sounds of a fast-moving glacial ice-stream calving into a fjord covered by icebergs makes for a dramatic and awe-inspiring natural phenomenon.

Cocos Island National Park

Cocos Island National Park, located 550 km off the Pacific coast of Costa Rica, is the only island in the tropical eastern Pacific with a tropical rainforest. Its position as the first point of contact with the northern equatorial counter-current, and the myriad interactions between the island and the surrounding marine ecosystem, make the area an ideal laboratory for the study of biological processes. The underwater world of the national park has become famous due to the attraction it holds for divers, who rate it as one of the best places in the world to view large pelagic species such as sharks, rays, tuna and dolphins.

Canadian Rocky Mountain Parks

The contiguous national parks of Banff, Jasper, Kootenay and Yoho, as well as the Mount Robson, Mount Assiniboine and Hamber provincial parks, studded with mountain peaks, glaciers, lakes, waterfalls, canyons and limestone caves, form a striking mountain landscape. The Burgess Shale fossil site, well known for its fossil remains of soft-bodied marine animals, is also found there.