BASIN ASKYA

Unfortunately, this inaccessible region still poorly understood. Huge tufa shaft Aski, covering an area about 55 km, flanked on the outer and inner sides of numerous craters. In the south-east corner is a lake, surrounded by strong fumaroles and several craters that are 2 and 3 January 1875 threw basalt and tuff rocks. March 29 there was a terrible eruption of pumice: ash flew to Stockholm. Bottom of the crater is now turned into a green-blue, constantly boiling and bubbling glinopodob-ing mass. With the noise and roar erupt from the crater of the huge pillars of steam and a lot of small steam jets, which are dispersed in the form of rays. Aski activity represents a contrast to the activity of volcanoes, located on the cracks, it is - the only volcano, Iceland, thrown into the historical times this white pumice. Movement of the earth's crust in the north-easterly direction, typical for southern Odada-Rauna. also observed at the foot of the glacier Wathne. They have a decisive influence on the location of volcanoes throughout the South and West Iceland, Reykjavik, nesa Peninsula and the region's famous Gackle. The latter is tuff tree, reaching 20 km in length and accompanied by numerous craters. In addition to volcanic fissures, and relatively less common volcanic tuff, in Iceland there is another great type of burning mountains: it - flat shield-shaped volcano with a huge crater, which resembles its shape pit mine and throws out lava. Such volcanoes reach a huge development on the island of Hawaii, and therefore a detailed description of them, we repent to another location. Whether this similarity and on the activities of the Icelandic volcanoes, we can not solve, since they are already faded. By Toroddsenu greatest volcanoes of this type are Trella-Ding-Ding and Kollota in Odada-Rauna and Stirtur in Central Iceland, between Hofs-iokulom and Long iokulom. Keylhak refers here yet volcano Skyalbreyd (large shield), located north of Lake Tingvalla. Trella Ding reaches the height of 1491 meters above sea level, and in diameter up to 15 km. Kollota Ding somewhat lower. Slopes of these extremely flat volcanic domes-tilted slightly - from F to 10th. They are formed exclusively by numerous lava cover with a small cinder cones on the outer surface and inside the cavities. At the top is a huge round or elliptical crater with an extremely steep walls. Toroddsen believes that within the crater as well as in the Hawaiian volcanoes, lava lakes are located. In the south-western Iceland, in the dissemination of basalts, there are many small volcanoes on the shores of the Gulf Faksaford. Their arrangement appears to be very interesting: as shown Toroddsen, they form a semicircle on the shore of the bay, and lie on the cracks, of which hit the warm carbonated keys. Thus, Fax bay is like the rest extinct basin. With regard to the chemical composition of lavas of Iceland, they have in most cases, the main character. However, there are also acidic lava - liparites, pumice, and in recent times, and obsidian flows. An example of the latter may serve Itrafutinu-Raun in Gackle, and some streams have Krafly, the Turf-iokula and especially in Iokulbarmura inside the island. With regard to external properties of lava flows, in Iceland, as in any other volcanic area, one can distinguish two major forms: the so-called "Hell Rauna" and "apal-Rauna": the first corresponds to the wavy lava "pahoehoe", the second - blocky "aa" Hawaiian volcanoes. Blocky lava surface is reminiscent of the troubled sea, is in Iceland on a smaller area, the predominant here wavy lava has a very pronounced plitnyakovym structure. The mass of lava thrown out by Icelandic volcanoes, unusually enormous, estimated Toroddsena, one just north-east of the island, between Iokulso and Skalfandaflyut it reaches 216 cubic meters. km. Suggest that since the settlement of the island in the IX century eruptions occurred twenty volcanoes, most of them are accounted for by Gackle (21) and Cuttle (12). Continuation of the volcanic chain, obliquely penetrates Iceland can be regarded as the island of Jan Mayen, situated further north. The highest pinnacle of his, Berry Mountain, covered with glaciers and reaches 2,545 m. This is an extinct volcano. Lower Mountains Jan Mayen, as well as the mountain is located nearby Egg Island detected volcanic activity in recent years. Fig. 184 depicts a mountain berry, with its numerous parasitic craters, and Fig. 185 submitted Bird Mountain, the ruined crater that burst into the sea. By Berry Mount adjoins long and narrow spit, which is directed toward the southwest. It is covered with numerous small craters that erupted basaltic lava. Outside Iceland, the Atlantic Ocean at a great distance, and do not represent the traces of volcanic activity. On the whole east coast of America from the Arctic Circle to Tierra del Fuego and on the west coast of Europe and Africa to the north of the equator, we find not a single volcano. Only in the middle of the Gulf of Guinea is located some but not acting, but well-preserved volcanoes: among them are Mount Cameroon, which reaches 4000 m in height, the island of Fernando Po, Principe, St. Thomas and Annobom. Ancient Volcano, located near Lake Chad, is probably the north-east spur of this kind. To the southwest extension of the line of Cameroon is an island of St. Helena, with its extinct crater. Here a number of volcanoes, it seems, gives a new spur, towards the north-west and going through the Ascension Island to the island of St.. Paul. If so, the island of St.. Helena should be considered as a place of intersection of the two volcanic lines. Perhaps, and Tristan da Cunha, an island located farther to the south, is in connection with a crack that runs well on the island of St.. Helena; how this is true, yet can not be solved.