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Millions of visitors flock to our nation's amazing national parks each year. More than just weekend getaways, these parks are home to mind boggling geologic formations that show the Earth's hard work through the ages.
From geysers to the Grand Canyon (pictured above), here are eight favorites. After touring them, go out and see them in person. All parks are open free of charge this week during National Parks Week.
Sandstone Arches - Arches National Park, UtahSlide 2 of 17
Sandstone Arches - Arches National Park, Utah
The forces of nature have acted in concert to create the landscape of Arches, which contains the greatest density of natural stone arches in the world.
Throughout the park, rock layers reveal millions of years of deposits, erosion and other geologic events. These layers continue to shape life in Arches today, as their erosion influences elemental features like soil chemistry and where water flows when it rains.
Arches National Park is located in a "high desert," with high elevations, very hot summers, cold winters and very little rainfall. Even on a daily basis, temperatures may fluctuate as much as 50 degrees Fahrenheit (28 degrees Celsius). The plants and animals in Arches have many adaptations that enable them to survive these conditions.Slide 3 of 17
Moonbow at Yosemite Falls - Yosemite National Park, CaliforniaSlide 4 of 17
Moonbow at Yosemite Falls - Yosemite National Park, California
Yosemite National Park, one of the first wilderness parks in the United States, is best known for its waterfalls. One waterfall stands out above the rest, not necessarily because of the waterfall itself, but due to a phenomenon called a moonbow.
A moonbow is basically a rainbow that appears as the moon sets, but it only happens a few times each year as light is reflected off the surface of the moon rather than from direct sunlight.
Lucky park goers can witness this dazzling color display at Yosemite Falls. To see a moonbow at Yosemite Falls you need clear skies, enough water in the falls to create sufficient mist, dark skies, and bright moonlight not blocked by the surrounding mountains.Slide 5 of 17
Old Faithful Geyser - Yellowstone National Park, WyomingSlide 6 of 17
Old Faithful Geyser - Yellowstone National Park, Wyoming
Yellowstone is America's and the world's first national park and home to wildlife such as grizzly bears, wolves, bison and elk. But the park's big draw is its famous collection of water-spewing geysers that make up nearly 60 percent of the world's geysers.
The famous Old Faithful is a cone geyser in Wyoming that can shoot up to 8,400 gallons (32,000 liters) of piping hot water up to 185 feet (56 meters) into the air. The waterworks can last up to 5 minutes long. Eruptions are currently about 90 minutes apart.
Geysers are temporary geological features, lasting only a few thousand years. Intense volcanic heat, underground water and natural geologic plumbing fractures, fissures and other open spaces in rock through which the heated water can escape are required to create a geyser. As the water boils underground, a column of water and steam is blasted out of the geyser's opening. [Infographic: The Geology of Yellowstone]
Yellowstone has more to offer than just geysers of course; the park covers more than 3,472 square miles (8,987 sq km) filled with lakes, canyons, rivers and mountain ranges.Slide 7 of 17
Grand Canyon - Grand Canyon National Park, ArizonaSlide 8 of 17