10 most difficult ge­og­ra­phy of North America riddles

White Sands, having 442 total square kilometers of dune fields, is the world's largest surface deposit of gypsum. Unlike other desert sands, it is cool to the touch, due to the high rate of evaporation of surface moisture and the fact that the sands reflect, rather than absorb, the sun's rays.

Yukon, having 1,979 mil (3,185 km), is just 223 miles shorter than Mississippi. Despite its length, there are only four vehicles-carrying bridges across the river.

In a three year journey between 1903 and 1906, Amundsen explored the passage with a crew of no more than six, in the converted 47-ton herring boat Gjøa. Spending winters with ship trapped in ice, he learned from the local Netsilik people about Arctic survival skills that would later prove useful. For example, he learned to use sled dogs and to wear animal skins in lieu of heavy, woolen parkas. Amundsen later led the expeditions to discover the South Pole (1911) and the North Pole (1926).

The gradient between The Great Lakes is generally very shallow. However, the descent between Erie and Ontario is greater than between any of the others, and includes the spectacular Niagara Falls, 51m high.

Rio Grande is the fourth or fifth longest river system in North America, but it flows through arid and desert regions. The average discharge is just 82 m³/s (St Lawrence: 10100, Yukon: 6200, Colorado: 1200). It is also very variable, occasionally rising to over 10000 m³/s or dropping to 1 m³/s. During portions of 2001 and 2002 the mouth of the Rio Grande was blocked by a sandbar.

Vancouver is one of Canada's warmest cities. The city has a moderate oceanic climate. On average, there are only eleven days of snowfall per year.

According to the 2000 census, 281,069 U.S. citizens self-identify as Cherokee. These numbers are closely followed by Navajo (269,202). Other tribal groups are considerably smaller, only Sioux (108,272) and Chippewa (105,907) exceed 100,000.

Malibu is a 21-mile beach community in Los Angeles County, California. The city name is derived from "humaliwo", meaning "the surf sounds loudly" in the language of the Chumash, Native American tribe.

Kīlauea is one of the most active volcanoes on the planet and an invaluable resource for volcanologists who are able to study it up close due to its exclusively non-violent effusive activity. Kīlauea lacks a distinct peak and lies close to Mauna Loa.

The 4 most populous states are California (38M), Texas (26M), New York (19M) and Florida (19M).