volcanoes Volcanoes are cracks in the earth's crust that spray materials in liquid, solid and gas A GENERIC VOLCANO IS FORMED BY : a basin or MAGMA CHAMBER, ie the underground tank in which is present the magma that feeds the volcano. a fire or volcanic conduit( VENT) main transit point of magma from the magma chamber to the surface. a summit CRATER, where flows the main line. one or more secondary ducts( CONE), which, flowing from the flanks of the volcano or from the same base, give life to secondary cones and craters. of the side slits, cracks on the longitudinal side of the volcano, caused by the pressure of the magma. They allow the escape of lava form of eruption fissure. V OLCANOES ERUPTION V OLCANOES ERUPT LAVA IN VARIOUS WAYS ACCORDING TO THE TYPE OF MAGMA FROM WHICH IT ORIGINATES. I F THE LAVA IS VISCOUS ( SILICA - RICH LAVA ) ERUPTION IS VIOLENT AND OCCURS AS A COLOSSAL EXPLOSION : THE SO - CALLED VOLCANIC BOMBS ( PYROCLASTIC ROCKS ). Volcanoes erupVtion Aa and pahoehoe are terms referring respectively to clinkery, rough-textured, higher-velocity flows, and less viscous, smooth-textured, lower-velocity flows. More silica-rich magmas produce block-lava flows, whose surfaces consist of dense solidified blocks, and obsidian flows, which contain large masses of glassy, crystal-poor rocks. We have active volcanoes (under solfataric, permanent or moderate eruption) dormant volcanoes and extinct volcanoes. Those definitions mean different things to different people and to different volcanoes. One of the simpler ways to answer is that an active volcano is one that has erupted since the last ice age (i.e., in the past 10,000 years. A dormant volcano would then be one that hasnt erupted in the past 10,000 years, but which is expected to erupt again.active volcanodormant An extinct volcano would be one that nobody expects to ever erupt again.extinct Virginias dormant vulcanoes Extinct volcano in Haway What is the largest active volcano? The largest volcano that still has a regular activity is the MAUNA Loa in Hawaii. Cone has a length of 120 km and a diameter of 103, and its crater is 10 km wide, the volcano is 4186 m high. Which country has the most volcanoes? L 'INDONESIA (about 200), it is located in the "Ring of Fire", an area of great volcanic activity around the Pacific. When was the largest volcanic eruption? In 1883 the island of Krakatoa, between Java and Sumatra, in Indonesia, exploded, it is estimated that this eruption has developed a power equal to 26 hydrogen bombs What caused the damage Krakatoa? The explosion of KRAKATOA caused the death of more than 36,000 people, many of them were drowned by the tidal wave, high around 50 m, created by the eruption and fell on nearby islands. Stromboli The few active volcanoes costantly in Europe In mediterranean sea, near Sicily. Secondary volcanism( vulcani spenti)represents a series of phenomena which are the secondary manifestation of the activity of a volcano or when the volcano is declared off, but the residual magma continues to interact with the ground, these phenomena are the geysers and hot springs, fumaroles, the mofete, the geysers, the sulphurous, sauces. Underwater volcanoes A third type of volcanic submarine volcanoes are in the form of simple cracks in the oceanic crust from which magma and gases escaping. Geyser in Andernach, Germany Calderas ("supervolcanoes") Although not recognized as true volcanoes, deserves a separate discussion on the case of 7-8 large calderas identified on the Earth's surface. These structures are characterized by not having a volcano rather than a depression of volcanic origin (called caldera), which covers a vast area, more than km. CALDERAS A CCORDING OF THE I NTERNATIONAL A SSOCIATION OF V OLCANOLOGY, ACTIVE V OLCANOES ARE 1500 ON EARTH ( 90% UNDERWATER ) LOCATED IN AREAS THAT CORRESPOND TO AREAS OF HIGH SEISMICITY. T HESE AREAS CAN BE GROUPED INTO FOUR MAIN AREAS : 1. THE SO - CALLED "R ING OF F IRE " IN THE P ACIFIC, WHICH FOLLOWS THE EASTERN AND WESTERN MARGINS (A LEUTIANS, A LASKA, THE R OCKY M OUNTAINS AND THE C ASCADES CHAIN, C ENTRAL A MERICA WITH THE BRANCH OF THE A NTILLES AND G ALAPAGOS, A NDES, A NTARCTICA, N EW Z EALAND P ACIFIC I SLANDS W ESTERN E UROPE, J APAN, K AMCHATKA ) AND THE CENTER OF THE P ACIFIC (H AWAII ) 2. THE M EDITERRANEAN REGION AND C ENTRAL AND S OUTH A SIA, ALONG THE A LPINE -H IMALAYAN CHAIN RECENT (A TLAS, SOUTH - CENTRAL I TALY, G REECE, T URKEY, THE C AUCASUS, I RAN, T IBET, THE S UNDA I SLANDS ), TO WHICH YOU CAN CONNECT THE VOLCANOES FORMED IN THE RIGID AREAS OLDEST THE EDGE OF THE CHAINS (A UVERGNE, H ERCYNIAN MASSIFS OF G ERMANY, D ECCAN ) 3. LINES OF FRACTURES OF THE A TLANTIC (A RCTIC, I CELAND, THE A ZORES, THE C ANARY I SLANDS, DORSAL -A TLANTIC ) 4. THE GREAT RIFT VALLEYS OF E AST A FRICA WHICH ARE STILL IN A RABIA, THE M IDDLE E AST AND ON THE BOTTOM OF THE I NDIAN O CEAN. DIFFERENT TYPES OF VOLCANOES B ECAUSE OF THEIR SHAPE AND THE ACTIVITY THAT CHARACTERIZES THEM, THE VOLCANOES ARE DIVIDED INTO FOUR MAIN TYPES : THE SHIELD VOLCANOES, OR H AWAIIAN, GLISTRATOVULCANI, THE S TROMBOLIAN VOLCANOES AND VOLCANOES PELEANI. VOLCANOES A SHIELD They are also known as the Hawaiian Islands Hawaii are nothing more than a collection of volcanoes, which are characterized by the issue of very fluid lava, high temperature up to 1200 C. the gas out slowly from magma, without giving rise to outbursts, The sides of these volcanoes, which reach considerable heights, they are always sweet. The stratovolcanoes Alternating periods in which the activity is characterized by the issue of lava periods in which they are issued mainly ash, lapilli and volcanic bombs.Stratovolcanoes volcanoes are some of the most "famous" of the world: Vesuvius, the Fujiyama in Japan, Krakatoa in Indonesia and Popocatepetl in Mexico. The nature of their activity makes them particularly hazardous: the ash clouds and high temperature gas, which emit in their explosions, can rise up to 20 km in height and then precipitate covering the whole with layers of ash boiling even several meters thick. This is what happened in the explosion of Vesuvius that destroyed the cities of Pompeii and Herculaneum in 79 AD VOLCANOES S TROMBOLIAN THEIR MAGMAS ARE VISCOUS AND THIS CAUSES THE GAS TO BE FREED WITH VIOLENCE DRAGGING WITH IT A LARGE QUANTITY OF SCORIA. T HE LAVA FLOW A LITTLE FASTER AND SO THE VOLCANO HAS STEEP SIDES. VOLCANOES PELEANI They take their name from the Pele volcano, which is located in Martinique. Their magmas are so viscous lava, almost unable to flow and form domes or spiers around the crater. Gases of magma are released with great violence, carrying with it dust and slag forming huge clouds at very high temperatures and hot clouds, which collapse under their own weight and fall like an avalanche along the flanks of the volcano, destroying everything they encounter on their way Classification of IGNEOUS ROCKS Intrusive rocks extrusive rocks BASAL T granite syenite diorite gabbroporphyrytrachyte andesite basalt Ejecta: Bombs, Blocks, Cinders, Clinkers, Glass (obsidian), Pumice and Ash Obsidia n (black volcanic glass) and Pumice (only rock that floats on water) Can Volcanoes affect humankind in many ways? Generally volcanoes cause destruction and loss of human lives, but also bring benefits, because the volcanic soil is fertile and rich. The volcanic rocks are also an excellent material for road construction( BASALT). The enormous heat generated from volcanoes could then be exploited to obtain electricity or to supply the houses of hot water. Over geologic time, volcanoes recycle the Earths hydrosphere and atmosphere and explosive eruptions affect positively the climate. Tourism in sulfur Therme in Vulcano isle Sulfur mines in indonesia