is the grand canyon the largest canyon in the us
Grand Canyon The Grand Canyon is a river valley in the Colorado Plateau that exposes uplifted Proterozoic and Paleozoic strata, and is also one of the six distinct physiographic sections of the Colorado Plateau province. It is not the deepest canyon in the world (Kali Gandaki Gorge in Nepal is much deeper). However, the Grand Canyon is known for its visually overwhelming size and its intricate and colorful landscape. Geologically, it is significant because of the thick sequence of ancient rocks that are well preserved and exposed in the walls of the canyon. These rock layers record much of the early geologic history of the North American continent.
Niagara Falls, Ontario The city is built along the Niagara Falls waterfalls and the Niagara Gorge on the Niagara River, which flows from Lake Erie to Lake Ontario.
Dust Bowl This catastrophe intensified the economic impact of the Great Depression in the region.
Grand Canyon Nearly two billion years of Earth's geological history have been exposed as the Colorado River and its tributaries cut their channels through layer after layer of rock while the Colorado Plateau was uplifted.[4] While some aspects about the history of incision of the canyon are debated by geologists,[5] several recent studies support the hypothesis that the Colorado River established its course through the area about 5 to 6 million years ago.[1][6][7] Since that time, the Colorado River has driven the down-cutting of the tributaries and retreat of the cliffs, simultaneously deepening and widening the canyon.
Grand Canyon The Grand Canyon is part of the Colorado River basin which has developed over the past 70 million years,[12] in part based on apatite (U-Th)/He thermochronometry showing that Grand Canyon reached a depth near to the modern depth by 20 Ma.[13] A recent study examining caves near Grand Canyon places their origins beginning about 17 million years ago. Previous estimates had placed the age of the canyon at 5â€“6 million years.[14] The study, which was published in the journal Science in 2008, used uranium-lead dating to analyze calcite deposits found on the walls of nine caves throughout the canyon.[15] There is a substantial amount of controversy because this research suggests such a substantial departure from prior widely supported scientific consensus.[16] In December 2012, a study published in the journal Science claimed new tests had suggested the Grand Canyon could be as old as 70 million years.[17] However, this study has been criticized by those who support the "young canyon" age of around six million years as "[an] attempt to push the interpretation of their new data to their limits without consideration of the whole range of other geologic data sets."[14]
Great Plains The region is known for supporting extensive cattle ranching and dry farming.