Page:Africa by Élisée Reclus, Volume 3.djvu/41

 CLIMATE OF THE AZORES. 25

western group, least in extent, population and historical importance, comprises only the two remote islets of Flores and Corvo, which are alone disposed in the direction from north to south, all the others forming volcanic chains running north-west and south-east. A comprehensive study of the whole archipelago shows that it constitutes three such parallel chains equidistant from each other, the first formed by Graciosa, Terceira, and San-Miguel, the second, or central, by Corvo, San- Jorge, and the Formigas, the third, or southernmost, by Flores, Fayal, Pico, and Santa-Maria. The regular parallelism is perhaps to be attributed to successive eruptions occurring on fractures or crevasses in submerged ridges aligned in the direction from north-west to south-east.

The lavas of the Azores are much more recent than those of Madeira and the Canaries, none appearing to be older than the Miocene period, that is, the epoch whence date the limestone formations of Santa-Maria. At present the volcanic activity, if not extinct, is at least very quiescent at the two extremities, that is, on the one hand in Santa-Maria and the eastern part of San-Miguel, on the other in the Flores and Corvo group. But the fires still rage under the central islands, especially under the volcano of Pico, and still more fiercely in the western part of San-Miguel. Here have occurred all the most terrible catastrophes, eruptions, and earthquakes during the four centuries that constitute the historic period of the Azores.

Indications of upheaval are visible in Terceira, where the beach, although composed entirely of volcanic rocks, is, at certain points, strewn with boulders of crystalline and sedimentary origin, such as granites, quartz, schists, sandstones, and limestones. These foreign fragments have evidently been deposited on the strand, but are now scattered to a distance of over half a mile inland in sufficient abundance to be used by the peasantry, with detached blocks of lava, in the con- struction of their enclosures. On Santa-Maria are also found some fragments of gneiss, the origin of which it is difficult to determine. The great depth of the surrounding waters excludes the idea that they might have been torn from some surviving reefs of the submerged Atlantis. Nor are these blocks rounded like the shingle long exposed to the action of the waves, but have for the most part pre- served the sharp outlines and freshness of their breakage. Hartung supposes that they may have been brought during the glacial period from America, where, under the same latitude, the glaciers deposited their moraines, while detached boulders were carried with the drift ice to the Azores.

Climate.

All these islands enjoy an equable and healthy climate, which would seem almost perfect but for the violence of the Atlantic gales. IN'otwithstanding the sudden shifting of the winds, the changes of temperature are very slight, the seasons following each other without any marked transitions. Autumn especially delights the visitor, although the leafy groves lack those varied tints which at that period are characteristic of the European, and still more of the North