PHYSICAL GEOGRAPHY 223 



Large areas of Iceland are, moreover, covered with volcanic 

 ashes, slags and bombs ejected by volcanoes. During the eruptions, 

 the fine ashes are often spread out over a large part of the country 

 and are sometimes carried by the wind across the Atlantic Ocean. 

 During the Katla eruption in 1625, the ashes were carried to Bergen 

 in Norway, and in 1845, ashes from Hekla were carried as far as 

 to Germany, and during the Askja eruption in 1875 the volcanic 

 dust was carried to the west coast of Norway in eleven hours forty 



/ V 



minutes, and in another ten hours they travelled as far as Stock- 

 holm. Ashes and slag are thrown up into the air to a great height; 

 on April 21, 1766, the ash-column of Hekla had a height of 5000 

 metres above the summit of the mountain, and it has often been 

 higher still. Lava fragments and bombs are shot into the air to a 

 great height and often fall at a distance from the place of eruption; 

 during the Hekla eruption in 1510, a man was killed by a volcanic 

 bomb at Skalholt, 45 km. from the volcano; during the eruption 

 of the same mountain in April 5, 1766, a volcanic slag, as big as 

 a man's fist, was hurled to Vidivellir in Skagafjor5ur, 165 km. from 

 the mountain. The fine dust which fills the air during great erup- 

 tions, causes peculiar refraction-effects in the air; thus, during the 

 Laki eruption of 1783, dust-clouds and unusually brilliant sunsets 

 were common over the whole of Europe, North Africa and a part 

 of western Asia. The ashes fell in such quantities in Caithness in 

 Scotland as to destroy the crops; that year is still spoken of by 

 the inhabitants as "the year of the ashie." The shower of ashes, 

 together with the red-hot scoriae ejected in an eruption, often causes 

 considerable damage to the inhabited land. Pastures are buried 

 beneath them or are scorched, and the coppice-woods often suffer 

 severely. Whether the damage done by the ashes to pastures is 

 permanent or not greatly depends upon their nature; the heavy 

 basaltic ashes are especially injurious, as they can only with diffi- 

 culty be carried away by the rain or by irrigation. When, however, 

 the layer of ashes is thin it gradually is absorbed into the soil, by 

 the grass growing up above it. In the neighbourhood of larger 

 volcanoes, several layers of ashes, one above the other, are found 

 in the soil. The light, liparitic pumice-ash, which is rarer, is less 

 injurious, as it is quickly carried away by water. Sometimes the 

 ashes discharged by a volcano contain a great quantity of acids; 

 during the Laki eruption of 1783, the ashes were so acid that they 

 burnt holes in the burdock leaves, and left black patches on the 



