The extraordinary number of craters, a few of which are reported still to be active, gives evidence that the archipelago is the result of volcanic action.
The number of main craters may be about twenty-five, but there are very many small eruptive cones on the flanks of the old volcanoes.
All the other lakes of Central Italy, which are scattered through the volcanic districts west of the Apennines, are of an entirely difierent formation, and occupy deep cup-shaped hollows, which have undoubtedly at one time formed the craters of extinct volcanoes.
There are raised coral beds high up the mountains, and lava occurs in a variety of forms, even in solid flows; but all active volcanic agency has so long ceased that the craters have.
Of its nearest neighbour, and therefore scarcely belongs geographically to the group, all the islands are considerably elevated, with several extinct or quiescent craters rising from 2000 ft.
A line of craters is seen to the south-west.
They are merely craters raised above the level of the surrounding country by the gradual accretion of the soft oily mud, which overflows at frequent intervals whenever a discharge of gas occurs.
On the summit of Ontake are eight large and several small craters, and there also may be seen displays of trance and divine possession, such as are described by Mr Percival Lowell in Occult Japan (1895).
At the summit are two deep craters, the southern of which emits steam.
Fergusson Island clearly shows remains of extinct craters, and possesses numerous hot springs, saline lakes and solfataras depositing sulphur and alum.
Besides a number of true volcanic craters (Lokobe, the highest point, is 1486 ft.
Poas (8895), the scene of a violent eruption in 1834, begins a fresh series of igneous peaks, some with flooded craters, some with a constant escape of smoke and vapour.
Cinder cones and tufa cones abound, but one of the most distinguishing features of the Hawaiian volcanoes is the great number of craters of the engulfment type, i.e.
Pit-craters which enlarge slowly by the breaking off and falling in of their walls, and discharge vast lava-flows with comparatively little violence.
That those to the westward have long been inactive is shown by the destruction of craters by denudation, by deep ravines, valleys and tall cliffs eroded on the mountain sides, especially on the windward side, by the depth of soil formed from the disintegrated rocks, and by the amount as well as variety of vegetable life.
Cinder cones are the predominant type of craters on both Mauna Kea and the Kohala Mountains, and they are also numerous on the upper slopes of Mauna Hualalai; but the more typically Hawaiian pit or engulfment craters also abound on Mauna Hualalai and Mokuaweoweo, crowning the summit of Mauna Loa, as well as Kilauea, to the S.E.
There are few craters on the loftier heights, but on the coasts there are several groups of small cones with craters, some of lava, others of tuf a.
The mountainous regions contain numerous lakes, many evidently occupying the craters of extinct volcanoes.
When, as sometimes happens, two or three of these craters have merged into one, the lake attains a great size.
In the third, after the Campagna, by a great general uplift, had become a land surface, volcanic energy found an outlet in comparatively few large craters, which emitted streams of hard lava as well as fragmentary materials, the latter forming sperone (lapis Gabinus) and peperino (lapis Albanus), while upon one of the former, which runs from the Alban Hills to within 2 m.
The two main areas near Rome are formed by the group of craters on the north (Bracciano, Bolsena, &c.) and the Alban Hills on the south, the latter consisting of one great crater with a base about 12 m.
Africa during the Cretaceous period (after the deposition of the Stormberg beds), and drilled these enormous craters through all the later formations.
There is now nothing to suggest twin deities; in ancient times there were probably two craters, whereas now there is only one.
These are of two classes - those of the bowl-like valleys and extinct craters of the mountainous region, Lakes.
Buch considered them to be representative of his "craters of elevation."
The remains of ancient craters can be distinguished, but their outlines have been greatly destroyed by denudation.
Lava covers most of the northern half of the range, and there are many craters and ash-cones, some recent and of perfect form.
In the Maribios district occur several volcanic lakelets, such as that of Masaya, besides numerous infernillos, low craters or peaks still emitting sulphurous vapour and smoke, and at night often lighting up the whole land with bluish flames.
Towards the south the country is very rugged and a series of extinct volcanic craters occur.
The tufa deposits which radiate from it extend as far as Rome; various small craters surround it, while the existence of warm springs in the district (especially those of Vicarello, probably the ancient Aquae Apollinares) may also be noted.
Beyond Posilipo is the small island of Nisida (Nesis); and at a short distance inland are the extinct craters of Solfatara and Astroni and the lake of Agnano.
Above its surface tower a great number of volcanoes and several craters, and its waters are alive with water-fowl, a multitude of ducks of various species breeding on its islands.
Altogether 107 volcanoes are known to exist in Iceland, with thousands of craters, great and small.
The largest volume of lava which has issued at one outflow within historic times is the stream which came from the craters of Laki at Skapta.
The Icelandic volcanoes may be divided into three classes: (I) cone-shaped, like Vesuvius, built up of alternate layers of ashes, scoriae and lava; (2) cupola-shaped, with an easy slope and a vast crater opening at the top - these shield-shaped cupolas are composed entirely of layers of lava, and their inclination is seldom steeper than 7°-8°; (3) chains of craters running close alongside a fissure in the ground.
For the most part the individual craters are low, generally not exceeding 300 to Soo ft.
There are often long intervals between the successive outbreaks, and many of the volcanoes (and this is especially true of the chains of craters) have only vented themselves in a solitary outburst.
The most remarkable 3 to M, about N N' feature of the surface comprises the craters, which are scattered everywhere, and generally surrounded by an approximately circular elevated ring.
W., through Nairai and Koro, to the Ringgold group in the N.E., have distinct craters, but their activity has long ceased.
In length and of varying width, and, reckoning in the adjacent island of Vivara, is made up of four extinct craters, parts of the margins of all of which have been destroyed by the sea.