In some respects the terrible outbreak of Skaptar Jokul has been several times exceeded. While almost alone in the immense quantity of lava thrown out, we have seen that great streams of lava are not accompanied by the most violent explosions. In the number of lives destroyed, Skaptar has also been exceeded; but if Iceland had been as densely populated as Ireland, which it equals in area, the convulsion might have destroyed half a million or more.
One of the best examples of the force of steam on a smaller scale is seen in the eruptions of volcanoes, is to be found in the geysers of Iceland. These lie in a strip of ground one hundred yards wide and about a quarter of a mile in length. The ground is dotted with numerous dark apertures and conical mounds, from which clouds of steam ascend continually. Of these the Little Geyser is no longer active, being merely a pool of still, hot water. The Great Geyser is periodically active, and the Strokr, or Churn, may be excited at any time by throwing a quantity of earth into it. As a matter of course, these boiling springs never do any damage, the quantity of water thrown out being of no consequence. The water holds in solution a vast quantity of silicious matter, which is deposited around the mouth of the geyser, forming sometimes a saucer-shaped basin, sometimes a nippleshaped mound. From the rate at which the deposits are made, it is estimated that the Great Geyser is about ten hundred and sixty years old.
One of the most tremendous outbursts of which we have any authentic account occurred in the island of Sumbawa. It is one of the Molucca islands; and the mountain from which the outbreak occurred is called Tomboro.
GEYSER.
“This eruption commenced on the 5th of April, 1815, but was most terrific on the 11th and 12th of that month; nor did it cease entirely until some time in the following July. The explosion so much resembled the firing of heavy cannon at a distance that the people of many vessels at sea supposed there was a great naval engagement within hearing, but could not imagine what nations were engaged.
“The commanders of some ships, and several English forts, gave orders to prepare for battle, though they were several hundred miles distant from the mountain. At Sumatra these tremendous explosions were distinctly heard, though not nearer than nine hundred and seventy miles from Tomboro. They were also heard at Ternate, in the opposite direction from Sumatra, at the distance of seven hundred and twenty miles from the mountain.