Canada is a federation composed of ten provinces and three territories. In turn, these may be grouped into regions: Western Canada, Central Canada, Atlantic Canada, and Northern Canada (the latter made up of the three territories Yukon, Northwest Territories, and Nunavut). Eastern Canada refers to Central Canada and Atlantic Canada together. Provinces have more autonomy than territories. The provinces are responsible for most of Canada's social programs (such as health care, education, and welfare) and together collect more revenue than the federal government, an almost unique structure among federations in the world. Using its spending powers, the federal government can initiate national policies in provincial areas, such as the Canada Health Act; the provinces can opt out of these, but rarely do so in practice. Equalization payments are made by the federal government to ensure that reasonably uniform standards of services and taxation are kept between the richer and poorer provinces. Canada occupies a major northern portion of North America, sharing land borders with the contiguous United States to the south and the U.S. state of Alaska to the northwest, stretching from the Atlantic Ocean in the east to the Pacific Ocean in the west; to the north lies the Arctic Ocean. By total area (including its waters), Canada is the second-largest country in the worldafter Russiaand the largest on the continent. By land area, Canada ranks fourth (land area is total area minus the area of lakes and rivers). Since 1925, Canada has claimed the portion of the Arctic between 60°W and 141°W longitude, but this claim is not universally recognized. The northernmost settlement in Canada (and in the world) is Canadian Forces Station Alert on the northern tip of Ellesmere Islandlatitude 82.5°N817 kilometres (450 nautical miles, 508 miles) from the North Pole.Much of the Canadian Arctic is covered by ice and permafrost. Canada also has the longest coastline in the world: 202,080 kilometres (125,570 mi). The population density, 3.3 inhabitants per square kilometre (8.5/sq mi), is among the lowest in the world. The most densely populated part of the country is the Quebec City Windsor Corridor, (situated in Southern Quebec and Southern Ontario) along the Great Lakes and the Saint Lawrence River in the southeast. The Horseshoe Falls in Niagara Falls, Ontario is one of the world's most voluminous waterfalls. It is renowned for both its beauty and as a valuable source of hydroelectric power. Canada has an extensive coastline on its north, east, and west, and since the last glacial period it has consisted of eight distinct forest regions, including extensive boreal forest on the Canadian Shield. The vastness and variety of Canada's geography, ecology, vegetation and landforms have given rise to a wide variety of climates throughout the country.Because of its vast size, Canada has more lakes than any other country, containing much of the world's fresh water. There are also fresh-water glaciers in the Canadian Rockies and the Coast Mountains.
Average winter and summer high temperatures across Canada vary according to the location. Winters can be harsh in many regions of the country, particularly in the interior and Prairie provinces, which experience a continental climate, where daily average temperatures are near −15 °C (5 °F) but can drop below −40 °C (−40.0 °F) with severe wind chills. In noncoastal regions, snow can cover the ground almost six months of the year (more in the north). Coastal British Columbia enjoys a temperate climate, with a mild and rainy winter. On the east and west coasts, average high temperatures are generally in the low 20s °C (70s °F), while between the coasts, the average summer high temperature ranges from 25 to 30 °C (77 to 86 °F), with occasional extreme heat in some interior locations exceeding 40 °C (104 °F). Canada is also geologically active, having many earthquakes and potentially active volcanoes, notably Mount Meager, Mount Garibaldi, Mount Cayley, and the Mount Edziza volcanic complex. The volcanic eruption of Tseax Cone in 1775 caused a catastrophic disaster, killing 2,000 Nisga'a people and the destruction of their village in the Nass River valley of northern British Columbia; the eruption produced a 22.5-kilometre (14.0 mi) lava flow, and according to legend of the Nisga'a people, it blocked the flow of the Nass River.