Properties of lava

Much more properties and composition of the lavas vary with certain regularity, first released a lava, then another. Usually preceded by basaltic trahitovye products. An example is Vesuvius: Somme is composed of rocks rich in silicic acid, on the contrary, during the latest eruption ejected poor silicic acid leucite lava. In some cases, after a period of basaltic volcanoes emit a short time trahitovye lava. In Hungary and in western North America Rihtofen a complicated sequence of different lavas. In these countries, products of ancient eruptions have strong basic character and are composed of propylene and andesite, then the acidity increases, trahirovye ejected lava and strongly acidic rhyolites, and finally again the basalts. This remarkable sequence, named after its discoverer scientist, observed in Japan, the Aeolian Islands and in other areas. Thus, in most cases the products emitted by volcanoes, are subject to known shifts. What is the reason for this phenomenon? Apparently, in the depths from which erupt lava, there are two dissimilar materials, occupying different regions: the same volcano lava gets from different areas. In most cases you can assume the existence of two regions: one delivers the lava rich in silica, the other - her poor, lava, occupying an intermediate position in its composition, are due to mixing. This idea is supported by research over the Bunsen lavas of Iceland: it showed that on this island are extremely representatives of both kinds. Some he calls normal trahitovymi rocks, while others - the normal pyroxene rocks (it would be better to call them basalt). The chemical composition of the following: Normal. Normally. trachytes basalts silica ...... 76.67 48.47 Alumina and oxide of iron. . 14.23 30.16 calcium oxide ...... 1.44 11.87 MgO ...... 0.28 6.89 potassium oxide ...... 3.20 0.65 Okii sodium ....... 4.18 1.96 Total .... 100,00 100,00 remaining rocks, the quantity of silica contained in them, occupy an intermediate position, they are considered as a mixture of normal trahitovyh and basaltic lavas. The percentage composition of these rocks are fully confirms this assumption. If, for example. In a rock found 53.08 per cent silica, it allows us to consider it as a mixture of 1 part trahitovoy weight and 5.117 pieces of basalt. You can calculate how much of alumina and iron oxide, lime, magnesia, etc., must contain rock and verify calculations of the direct analysis. The results of these comparisons are shown in the following table: Components of the breed I II III Found Calculated Found Calculated Found Calculated silica ...... 51.75 51.75 53.08 53.08 73.37 73.37 Alumina g of iron oxide. . 28.31 28.39 27.57 28.70 16.09 17.25 Lime ........ 10.65 10.49 10.16 9.92 2.66 2.49 MgO ..... 6.13 5.90 5.81 5.32 1.05 1.52 potassium oxide ....... 0.96 1.01 1.06 0.61 2.90 3.01 sodium oxide ...... 2.20 2.46 2.32 2.37 3.93 2.35 Sum 100.00 100,00 100,00 100,00 100,00 99,99 I. Breed of Reygadalr Foss at Gvammra (1 part trachyte, 7.597 pieces of basalt). - II. Rocks from Kalmanstungi (1 part trachyte. 5.117 pieces of basalt). - III. Foyolit from the mountains in Kalmanstungi Klett (1 part trachyte, 0.1325 parts of the basalt). This is a striking coincidence of the calculated and directly found by the composition seen in all Icelandic massive rocks. The same law are subject to many of the volcanic rocks of other localities, such as, for example., Rock Armenia Abikh investigated. However, there is not enough and these igneous rocks, which can not be regarded as a mixture of basalt trahitovoy masses: they contain, for example., A 76.87 per cent silica. It follows that to reduce all the massive rocks of the earth to two types of Bunsen's impossible, but as far as Iceland, the existence of two different masses, which feed its volcanoes, almost proved very likely that all rocks of any given area can be reduced to two main types, whose composition may be uneven or different, depending on the terrain.