Natural wonders of the world

Aurora

Auroras, also known as northern and southern (polar) lights or aurorae (singular: aurora), are natural light displays in the sky, particularly in the polar regions, and usually observed at night. They typically occur in the ionosphere. They are also referred to as polar auroras. This is a misnomer however, because they are commonly visible between 65 to 72 degrees north and south latitudes, which place them a ring just within the Arctic and Antarctic circles. Aurorae do occur deeper inside the polar regions, but these are infrequent and often invisible to the naked eye.

 

The Grand Canyon
The Grand Canyon is a massive rift 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 far deeper), nor the widest (Capertee Valley  in Australia is about 0.6 mi/1 km wider and longer than Grand Canyon); 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 beautifully preserved and exposed in the walls of the canyon. These rock layers record much of the early geologic history of the North American continent.The Colorado River basin (of which the Grand Canyon is a part) has developed in the past 40 million years.
Grand Canyon National Park is one of the world’s premier natural attractions, attracting about five million visitors per year. Overall, 83% were from the United States: California (12.2%), Arizona (8.9%), Texas (4.8%), Florida (3.4%) and New York (3.2%) represented the top domestic visitors. Seventeen percent of visitors were from outside the United States; the most prominently represented nations were the United Kingdom (3.8%), Canada (3.5%), Japan (2.1%), Germany (1.9%) and The Netherlands (1.2%).
Aside from casual sightseeing from the South Rim (averaging 7,000 feet [2,100 m] above sea level), rafting, hiking, running and helicopter tours[36] are especially popular. In October 2010 the North Rim is the host to an ultramarathon. The Grand Canyon Ultra Marathon  is a 78-mile (126 km) race over 24 hours. The floor of the valley is accessible by foot, muleback, or by boat or raft from upriver. Hiking down to the river and back up to the rim in one day is discouraged by park officials because of the distance, steep and rocky trails, change in elevation, and danger of heat exhaustion  from the much higher temperatures at the bottom. Rescues are required annually of unsuccessful rim-to-river-to-rim travelers. Nevertheless, hundreds of fit and experienced hikers complete the trip every year.