Yellowstone National Park

Sierra Nevada

Death Valley

Mt. Whitney

The center of the park is a caldera formed by a massive volcanic eruption.

Mesa Verde

Cherokee

Hummock or pocosin.

True

Desert

Behind the American portion of the Niagra falls

Walter Scott

worlds tallest trees

Normal volcanic activity. A lot of calderas worldwide, such as Yellowstone, California's Long Valley (site of the Mammoth Lakes ski area) and Italy's Campi Flegrei (near Naples) huff upward and puff downward repeatedly for decades to tens of thousands of years without catastrophic eruptions.
But nobody has any idea how long this process goes on before there either is an eruption or the inflow of molten rock stops and the caldera deflates again.

False

Fiji counts as a state can does not make up the four corners region

America must be more responsible in the use of pesticides that harm the environment.