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All About Volcanoes All about volcanoes ADITI10 Jakarta: Indonesia's Mount Merapi, one of the world's most active volcanoes, erupted twice on Sunday, sending clouds of grey ash 6,000 metres into the sky, the country's geological agency said. Indonesia has more than 17,000 islands and islets -- and nearly 130 active volcanoes. The Southeast Asian archipelago nation sits on the Pacific "Ring of Fire", a vast zone of geological instability where the collision of tectonic plates causes frequent quakes and major volcanic activity. Countries at highest risk of being struck by an earthquake in the Ring of Fire are in the US west coast, Chile, Japan and Pacific islands like the Solomon Islands. Other countries along the fault line include Mexico, Antarctica, Russia, Papa New Guinea, Indonesia, Canada, Peru, Taiwan, Philippines, and Guatemala India's only active volcanoes is located in Barren island of Andaman, which is also the only confirmed active volcano in South Asia. A volcano on Earth is a vent or fissure in the planet's crust through which lava, ash, rock and gases erupt. A volcano is also a mountain formed by the accumulation of these eruptive products. A volcano is an opening in the earth’s crust through which gases, molten rocks materials (lava), ash, steam etc. are emitted outward in the course of an eruption. Such vents or openings occur in those parts of the earth’s crust where the rock strata are relatively weak. Volcanic activity is an example of endogenic process. Depending upon the explosive nature of the volcano, different land forms can be formed such as a plateau (if the volcano is not explosive) or a mountain (if the volcano is explosive in nature). Magma vs Lava: The difference Magma is the term used to denote the molten rocks and related materials seen inside earth. A weaker zone of the mantle called asthenosphere, usually is the source of magma. •Once this magma came out to the earth surface through the vent of a volcano, it is called as the Lava. Therefore, Lava is nothing but the magma on earth surface. •The process by which solid, liquid and gaseous material escape from the earth’s interior to the surface of the earth is called as Volcanism. Volcanoes have existed for a long time on Earth, likely causing disasters such as the Permian mass extinction about 250 million years ago, the greatest mass extinction in Earth's history, according to a 2015 paper. Catastrophic volcanic eruptions that spewed enough lava to cover Australia led to the die-off at the end of the Permian era, the researchers found. That die-off occurred about 250 million years ago and was the greatest mass extinction in Earth's history; 90 percent of marine species and 75 percent of land dwellers were wiped off the face of the planet over the course of about 60,000 years. Ancient volcanic rocks now provide the best evidence yet that catastrophic volcanic activity triggered the extinction, researchers say. Volcanoes can and have existed on other worlds as well: although volcanoes on the moon and Mars have long been dormant, volcanoes are still very active on Jupiter's moon Io. Researchers are currently striving to find ways to predict when volcanic eruptions might happen on Earth by analyzing clues such as crystals and gases linked with volcanoes. How are they formed?? Earth's crust is 3 to 37 miles (5 to 60 kilometers) thick, according to the U.S. Geological Survey. It is broken up into seven major and 152 smaller pieces called tectonic plates, according to a 2016 paper by Christopher Harrison at the University of Miami. These plates float on a layer of magma — semi-liquid rock and dissolved gases. At the boundaries of these plates — where they move past, are pushed under, or move away from each other — magma, which is lighter than the surrounding solid rock, is often able to force its way up through cracks and fissures. Magma can explode from the vent, or it can flow out of the volcano like an overflowing cup. Magma that has erupted is called lava. Types Of Volcanoes According to shapes Shield Volcanoes They are not very steep but are far and wider. They extend to great height as well as distance. They are the largest of all volcanoes in the world as the lava flows to a far distance. The Hawaiian volcanoes are the most famous examples. Cinder Cone Volcanoes •Cinders are extrusive igneous rocks. A more modern name for cinder is Scoria. •Small volcanoes. •These volcanoes consist almost entirely of loose, grainy cinders and almost no lava. •They have very steep sides and usually have a small crater on top. Composite Volcanoes: •Shape: Cone shaped with moderately steep sides and sometimes have small craters in their summits. •Volcanologists call these “strato-” or composite volcanoes because they consist of layers of solid lava flows mixed with layers of sand- or gravel- like volcanic rock called cinders or volcanic ash. •These volcanoes often result in explosive eruptions. •Along with lava, large quantities of pyroclastic materials and ashes find their way to the ground. A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers of hardened lava, tephra, pumice and ash. Nevado Ojos del Salado is an active stratovolcano in the Andes on the Argentina–Chile border and the highest active volcano in the world at 6,893 m Caldera •These are the most explosive of the earth’s volcanoes. •They are usually so explosive that when they erupt they tend to collapse on themselves rather than building any tall structure. The collapsed depressions are called calderas. •Their explosiveness indicates that its magma chamber is large and in close vicinity. •A caldera differs from a crater in such a way that a caldera is a huge depression caused by a collapse after a large-scale eruption, whereas a crater is a small, steep side, volcanic depression bored out by an eruptive plume. Mauna Loa The largest volcano on earth is Mauna Loa on Hawai'i Big Island. It is a massive shieldvolcano constructed by countless lava flows. When measured from the base to the top, the pile of lavas measures more than 17,000 m (56,000 ft) Kilauea volcano on Hawaii is the world's most active volcano, followed by Etna in Italy and Piton de la Fournaise on La Réunion island. After that, it is difficult to decide the exact order on the list, but the following are very close: Stromboli, Merapi, Erta Ale, Ol Doinyo Lengai, Unzen, Yasur, Ambrym, Arenal, Pacaya, Klyuchevsky, Sheveluch, and Erebus. Nevado Ojos del Salado is an active stratovolcano in the Andes on the Argentina–Chile border and the highest active volcano in the world at 6,893 m (22,615 ft). This map shows the locations of the world's largest volcanoes. Tamu Massif on the Shatsky Rise in the northwest Pacific Ocean has the greatest mass and the largest footprint. Mauna Kea on the island of Hawaii has the greatest height from base to summit. Ojos del Salado in the Andes mountain range on the border between Argentina and Chile has the highest summit elevation. Step 4 Step 3 Step 3 16900 Step 5 StepStep 5 5 Step 4 Step 4 15210.
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