Composition of the lava of Mount Vesuvius

Composition of Somma lavas of the volcano - Vesuvius, over time, gradually changed. Volcano grand - Somma erupted trachyte with a lot of sanidine (sanidine-mineral from the group of feldspars) of Vesuvius since 1979, in contrast, poured out lava, rich in leucite (mineral from the group of potassium Field pshatov). The reason for this change Rittman sees that the magma chamber, who had an eruption, captures all the more and more "lateral rock", which started the formation of new minerals. Unexpectedly, also managed to establish precisely because of this new formation of minerals that the magma chamber is only 4 -5 miles below the earth's surface, therefore, within the Earth's crust, moreover, in the surface zone of Mesozoic limestone and dolomite deposits. In addition, the slow transformation of the lava during the past 12 thousand years occurred, and small individual changes its composition, if the intervals between eruptions were calculated for centuries (as, for example, before the eruptions in 1979 and 1631 gg.). In such cases, the magma chamber by a kind of "sorting" heavy minerals go down (gravitational differentiation), and if then begins an explosive eruption, the lava comes from the depths of different composition (for example, in 1979: first light and then dark pumice ). Similarly, changes and composition of the magma of the volcano Hekla, Iceland. "We have already mentioned about the large eruption of December 16, 1631, during which Naples has been bombarded with the 30 - centimeter layer of ash, 7 lava flows have flooded the streets of Boskotrekase, Torre - Annutsiato, Torre - del - Greco, Puglia n rubber. 4 thousand people were killed. Since that time, the activity of Vesuvius has acquired a certain rhythm. Periods of eruptions alternating with periods of rest] during which the volcanic forces resembled only the emissions of hot steam (fumaroles) ... Length eruption periods ranged from six months to a few tens of years, and periods of rest, from 2 -4 and 7 years (if not consider the current, much more long pause, lasting from 1944 r. Most of the eruptions began not very rapidly, in the depths of the crater, gradually crater completely filled with lava, and lava-platform with volcanic cone (BRC) at the center, rose a little higher, and finally, under the influence of ever-increasing workload is the collapse of the crater, lava poured out and committed violent, explosive eruption of the material. This is often a grand final phase and ends during the eruption; The result is a deep crater. Examples of these final phases can serve as the eruption of 1906 and 1944. In 1906, lava flows reached the city Boskotrekase, April 8 ash emissions had been destroyed in the Church of St. Giuseppe thawed, resulting in 105 people have died and, finally, a volcano during incessant electrical discharges began throwing huge clouds of steam. As of the huge steam boiler, from the crater during 18 hours with a deafening hiss (Perry likened it to a roar of Niagara Falls!) hit a pair of straight column height 13 km and an estimated amount of steam in line about 1 km 3 of water! Impressions of the last, tumultuous eruption in March 1944, retreated into the background before the war events, the Americans have already come to Naples. The lava flow destroyed the then town of San - Sebastiano.