If anyone wants to understand the immense firepower lurking under the surface of the Earth, they need only look at the spectacular explosions taking place all over the planet. National Geographic calls volcanoes “essentially vents on the Earth's surface where molten rock, debris and gases from the planet's interior are emitted.” And when this molten rock and gas builds up under the surface, the explosive emission is the stuff of legends. We still speak of the lost city of Pompeii, buried beneath a layer of ash from an erupting Mount Vesuvius in AD 79. The 1883 eruption of Krakatua in Indonesia is likewise universally known.
When a volcano becomes active, we are alternatively terrified and thrilled by its mysterious beauty. Check out these outstanding images of volcanic activity on Earth.
C.Heliker courtesy of USGS
Experts believe the Earth is covered in several shifting plates that rub against each other a few inches every year. This is called the plate-tectonics theory, which was developed in the 1960s. Below the plates exists the Earth’s mantle. The mantle is mostly solid with some hot pockets of liquid rock called lava. At times, this liquid rock rises to the surface amid cracks and fissures, and once it rises to this level, lava is called magma. When magma is less thick, it flows, and when it's thicker, it plugs up the surface, forming the familiar cone shape of volcanoes. When the magma becomes too thick to move, pressure builds … and awesome explosions are born.
Among the Earth’s most prolific hot spots are the Hawaiian Islands. Pictured above is lava spattering from the west vent in the West Gap Pit of Pu'u 'O'o on Oct. 3, 2003. Pu'u 'O'o is part of the Kilauea volcano of the Hawaiian Islands. Click here to view a webcam of this volcano, in addition to many U.S. volcanoes.
McGimsey and Game, courtesy of the Alaska Volcano Observatory/USGS
View east of Mount Redoubt
This photo, taken on March 31, 2009, shows the view east of Redoubt volcano with recent eruption deposits on the upper west-southwest flanks. Mount Redoubt is located in the Aleutian mountain range in what is known as the Ring of Fire, an area responsible for much of the Earth’s volcanic activity and earthquakes. In fact, more than half of the world's active, above-sea-level volcanoes encircle the Pacific Ocean to form the Pacific ring, according to the USGS. The Ring of Fire starts around New Zealand, runs up through Indonesia and Japan, arches over toward the Aleutian trench of Alaska, down through the North American West Coast and into the Peru-Chile Trench of South America. For an excellent visual of the Ring of Fire, look here.
M. Poland courtesy of USGS
Halema`uma`u plume with the moon
Pictured here is the Halema'uma'u crater located on the volcano of Kilauea in Hawaii. Hawaii exists outside the Ring of Fire in what is known as the Hawaiian Hot Spot. In 1963, Canadian geophysicist J. Tuzo Wilson provided an explanation for the existence of prolific volcanic activity in Hawaii. The USGS writes “According to Wilson, the distinctive linear shape of the Hawaiian-Emperor Chain reflects the progressive movement of the Pacific Plate over a deep immobile hot spot. This hot spot partly melts the region just below the overriding Pacific Plate, producing small, isolated blobs of magma. Less dense than the surrounding solid rock, the magma rises buoyantly through structurally weak zones and ultimately erupts as lava onto the ocean floor to form volcanoes.”
C.Dan Miller courtesy of USGS
Eruption of Mount St. Helens as seen from the south
On May 18, 1980, Mount St. Helens in Washington state erupted and scorched 230 square miles of forest. This photo, taken on Aug. 7, 1980, shows the ongoing eruption of Mount St. Helens. The volcano, which continued to erupt until 1986, began as an earthquake measuring 5.1 on the Richter scale. The forest service arm of the USDA described the event this way: “the north face of this tall symmetrical mountain collapsed in a massive rock debris avalanche. In a few moments, this slab of rock and ice slammed into Spirit Lake, crossed a ridge 1,300 feet high, and roared 14 miles down the Toutle River.” As many as 57 people died in the 1980 eruption. Some were as far as 13 miles away from the blast.
Courtesy of USGS
Photographer meets flow
There are about 1,900 active volcanoes on Earth and any one could explode at any time, says National Geographic. Still more volcanoes exist in a dormant state, which means they could become active again. Others are determined to be extinct. This is certainly not true of the Kilauea Volcano in Hawaii. The USGS writes of this photo: “Rather wide breakout coming from inflating tumulus (right) and moving slowly toward photographer. Note deep, widely spaced corrugations and wrinkles in crust on decelerating flow.” This photo was taken in April 2003.
In the last 300 years alone, around 260,000 people have died from volcanic eruptions. Nonetheless, scientists and adventurers continue to venture near them.
Eruption of the Rabaul caldera in Papua New Guinea
Papua New Guinea experiences prolific volcanic activity, largely due to an oceanic trench that lies south of the area. The USGS describes the trench this way: “Nearing the Solomons, the trench swings southeasterly, then down along the Vanuatu chain before turning east and ending below Hunter Island …. Tectonic complications in the form of two short oceanic spreading centers affect nearby volcanoes.” The Rabaul caldera volcano takes its name from the nearby town of Rabual. A caldera is a kind of depression that happens at the foot of a volcano when magma is withdrawn or erupts from a shallow magma reservoir.
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