Yellowstone National Park T o look at Yellowstone National Park today with its mature forests and imposing mountain ranges it’s hard to imagine the region ever being new But until 2 1 million years ago the entire area was beneath an expansive shallow sea Then the first of three major volcanic events took place Hundreds of cubic miles of ash and volcanic rock erupted from the seabed raising the land above the sea About one million years later lesser but still immensely powerful eruptions further altered the landscape The last major volcanic explosion occurred at Yellowstone about 640,000 years ago Scientists believe it was an enormous blast up to 100 times more powerful than the eruption that blew the top off Washington’s Mount St Helens in 1980 The eruption cracked the earth’s crust and vast amounts of ash and rock once again poured out giving shape to the landforms visible in Yellowstone today Yellowstone’s volcanic past is still evident Within the current Sitting atop a volcano Yellowstone is a land of steam with water heated underground creating various forms of hot springs
Preserving America park boundaries lies the Yellowstone Caldera The caldera which was created by the last major eruption covers more than 1,000 square miles 2,590 sq km and in fact sits upon an older larger caldera from a previous eruption Volcanic rock is visible throughout the region perhaps no more obviously than in Yellowstone’s Obsidian Cliff This wall of dark stone is composed of vertical columns that rise steeply from the prairie and tower over nearby pine forests Obsidian when cleaned and polished is shiny black and has the texture of glass The most obvious reminder of the region’s volcanic history is the hydrothermal activity that continues today The park contains about 10,000 hydrothermal features which is half of the total on Earth These features take several different forms but all share the basic ingredients of heat and groundwater Molten rock is only a few miles below the Yellowstone Caldera compared with the average distance of about 30 Grand Prismatic Spring is one of the most striking features in all of Yellowstone as this hot spring showcases a dazzling array of colors
