ICELAND

In the late Miocene or early Pliocene epoch, this vast basalt cover, has a capacity of more than 3000 meters, broke up. Much of it completely submerged in the sea, and Iceland gained broadly its current form. Basalts occupy the outskirts of Iceland. As shown Keylhak, they are cut by basaltic veins and huge cracks and provide a lot of sites, prolapsed due to discharges (Grabensenkungen). In general, this area is not large volcanoes. On the contrary, they occur in huge numbers in the southern, middle and northwestern parts of the country. Landscape is dominated by palagonitovye and tahilitovye tuffs, breccias and passing in concluding in its mass basaltic bombs and lumps of slag. Breed those still in many ways is not enough investigated. Keylhak distinguishes between two kinds of palagonitovyh tuffs: those who stand in connection with the basalt, it is viewed as a product of the first phase of volcanic activity, while those that cut across a wide belt recent volcanic area, connects with the latest eruptions. Torodtssen finds the latter more later formation than the Miocene basalts, and relates them to the era when the Central Iceland, settled for dumping site, there is a strong volcanic ash lapillts and bombs. Whatever the case, we should note that these tuffs are cut long crack, which is concentrated around the latest volcanic activity. The direction of cracks corresponds to the arcuate shape descended site. In West and South Iceland crack go to the east-northeast, in the middle part, they are deflected to the northeast and even in the north-northeast, and finally, in the northern part they are directed from north to south. Since ancient times along these lines, the dominant earthquakes, subsidence of entire areas of the earth's crust, volcanic eruptions and hit the hot keys. Among the Icelandic volcanoes, there are not many who, like Vesuvius, are steep cones are composed of tuffs and lava sheets and long time employees of the centers of eruption. Torodtssen mentions only two volcanoes of this type Snefels-iokul and Eyyafyalla-iokul. In most cases, fluid lava follows directly from the cracks all through, it spreads in all directions in the form of cover, or flows into a stream. Over the cracks usually a number of cones, consisting of cinders and lava, and they are located near each other, like a rosary, and resemble large volcanic parasitic cones: at least, their activity is limited by the eruption, during which they formed. If the lava starts to flow from the neighboring cracks, it is completely burying them en masse. Sometimes lava follows quietly, not making these fleeting side of the cones, are sometimes formed on both sides of the crack long shafts of dross and lava. One of the largest eruptions of this kind occurred in 1783 south of the glacier Skaptar in South Iceland. Fissure, erupting lava was directed to the northeast and over 24 km took place in palagonito of new tuffs, which are as few and small hills were made of basalt cover. First, lava poured from the west, and then from the eastern part of the crack. On both sides of the latter was at least 34 large and 60 small cinder cones and craters, most of them were only a few meters in height, and the highest crater rising 150 meters above the neighborhood. Lava spread on both sides of the crack, then ran to the shore in the form of two streams, each of length 45 km, and covered the surface of about 900 square meters. km. Helland, to whom we owe the first accurate description of this wonderful and magnificent eruption, suggests that the average power flow reached 30 meters, and total ejected masses - 27 cu. km. Crack Skaptar poured the most powerful of all known lava flows. Phenomena that accompanied this eruption, Reiher (as Hellandu) describes as follows (we give a description of several condensed version): "June 1, 1783 in the coastal areas there was an earthquake, which with a few interruptions lasted a whole week. In the north, the sky darkened, and the village fell down huge masses of volcanic ash. In the following days, coastal residents that the eruption occurring somewhere far away, and threatens their livelihood. June 10 at the north appeared fiery pillars, and to the consternation of people river Skapta, achieved primarily in the summer of 150 m in width, dried up. It was clear that from somewhere in the mountains rushed into the valley of lava flow and turned the water into steam. If the eruption stops, the lava is moving through the valley reaches the sea.