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In addition to those already referred to, a number of mysterious dark spots were discovered by Schmidt in the dusky region about midway between Copernicus and Gambart, which Klein describes as perforated like a sieve with minute craters. A short distance south-west of Copernicus stands a bright crater-cone surrounded by a grey nimbus, which may be classed with these objects.
This secondary crater-cone has been named Mount Shastina, and round its inner side the stream of glacier ice winds itself, sometimes surmounting the rim of the crater, and shooting down masses of ice into the great caldron. The length of this glacier is about three miles, and its breadth about 4000 feet.
The terraces observable within the craters in some instances have probably been left by subsequent eruptions which have not attained to the level of preceding ones; and where a central crater-cone is seen to rise within the caldron, we may suppose this to have been built up by a later series of eruptions of lava through the original pipe after the consolidation of the interior sea of lava.
Much more recent in appearance at least is the little isle of St. Eustatius, or at least the crater-cone, with its lip broken down at one spot, which makes up five-sixths of the island. St.
There are other forms of volcanic mountains, such as those built up of basaltic matter, of which I shall have to speak hereafter, but the two former varieties are the most prevalent; and we may now proceed to consider the conditions under which the crater-cone volcanoes have been formed. Crateriform Volcanic Cones.
Eustatius may have been in eruption, though there is no record of it, during historic times, and looks more unrepentant and capable of misbehaving itself again than does any other crater-cone in the Antilles; far more so than the Souffriere in St. Vincent which exploded in 1812. But these two are mere rocks. It is not till the traveller arrives at St.
But whilst rejecting the "elevatory theory," it is necessary to bear in mind that volcanic cones and dome-shaped elevations have been formed in several distinct ways, giving rise to varieties of structure essentially different. Two of the more general of these varieties of form, the crater-cone and the dome, are found in some districts, as in Auvergne, side by side.
This mountain, rising from the shore of the Bay of Baiæ, was suddenly formed in September 29th, 1538, and rises to a height of 440 feet above the sea-level. It is a crater-cone, and the depth of the crater has been determined by the Italian mineralogist Pini to be 421 English feet; its bottom is thus only 19 feet above the sea-level.
The summit of Mount Shasta is a nearly perfect cone, but from its north-west side there juts out a large crater-cone just below the snow-line, between which and the main mass of the mountain there exists a deep depression filled with glacier ice.
The first, Monte di Somma; the second, the cone of Vesuvius; and the third, the little crater-cone within the second. During this eruption, vast lava-sheets invaded the fields and vineyards on the flanks of the mountain. A vivid account of this eruption, as witnessed by Padre Torre, is given by Professor Phillips.
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