The Island of St. Michael (Azores) from the Journal of the Royal Geographical Society, Volume 15, 1845 to accompany "A Description of the Island of St. Michael (Azores). By Mr. Consul Carew Hunt. [Today the Portuguese equivalent is used: São Miguel] _______ THE J O U R N A L ROYAL GEOGRAPHICAL SOCIETY L O N D O N. VOLUME THE FIFTEENTH 1845. LONDON JOHN MURRAY, ALBEMARLE STREET. MDCCCXLV _______ 268 VI Description of the Island of St. Michael (Azores) By Mr. Consul Carl Hunt
1. This island, as delineated in the accompanying map, lies between the 25th and 26th meridians of W. Iong., a little S. of the 38th parallel of N. lat., describing a curved figure of pretty regular breadth as a whole, and occupying an area of 224 square miles. The chief town, Ponta Delgada, is at the W. side of a
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There is considerable variety in the aspect as the island is passed from E. to W. The E. end rises from a bluff sea-cliff of between l200 and 1400 feet elevation to a lofty inland peak, from which a central range, varying in helght between 2000 and 2500 feet, runs to the westward, terrminating in the Serra da Agoa de Pao, 3060 ahove the sea. The sea-coast gradually declines in approaching the last point, where it is not more than 100 feet high. The point next seen is lower, and its outline, as presented by the summits of numerous volcanic monticules of about l300 feet elevation, united in a central rridge more undulating; the western extremity being marked by the conspicuous Serra Gorda, 1574 feet above the sea
In the higher parts the surface is generally covered with an undergrowth of heaths, cedar, laurel, laurestinus, and other ever green shrubs, which give the mountains an exceedingly rich and wooded appearance, notwithstanding the inroads of cultlvation and the more destructive demand for fuel. Like all volcanic countries,the face of the island is uneven and irregular, being deeplv excavated by numerous ravines, and roughened by streams of semi-vitrified and scoriaceous lava that resist all atmospheric influences and repel vegetation. Heavy rains falling on the mountains afford a constant supply of water to 4 lakes at the bottom of extinct craters or subsidences, and a number of minor reservoirs, and through them to small streams rapidly running down on all sides into the sea.
The geological formation of St. Michael is volcanic, on a base in some parts of a whitish grey trachyte, in others basalt. The beds of lava lying between this and the surface are neither numerous nor thick, the height of the island being chiefly due to the accumulation of tufaceous and other softer depositions. Of the 7 or 8 successive beds, only parts of the uppermost have been formed since the discovery of the island, the others being of an unknown antiquity. Local historians have not been wanting, even in the earliest times, to record the various phenomena affecting the
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________ 270 ________geo]ogical character of the island, which may be given in the following chronological order:
A.D. 1445. It is stated that when the island was first discovered, it rose at the E. and W. ends into peaks of equal altitude; but the discoverers then leaving it and returning in the next year, were witnesses to a volcanic eruption that enveloped the W. end, when the peak had lost one-third of its height, presenting a broken line of truncation instead of its former cone. The scene of this change is the so-oalled valley of the Sette Cidades, a plain occupied partly by two lakes, partly by small hills, of pumlce and scoriae, 884 feet above the level of the sea, and surrounded by a ridge with peaks of between 1880 and 2810 feet elevation. The division marked A in the map was covered by this eruption and its showers of dust and stones.
A.D 1522. In the month of October of this year, the town of Villa Franca on the S. coast was destroyed by the fall of two considerable hills from their foundations, during the prevalence of an earthquake.
A.D. 1538. At the latter end of thls year a large islet, three miles in diameter, was thrown up in the sea N.W. of Mosteyros; but, being formed of loose matter, it soon disappeared, nor can any trace of it now be discovered. The ejection of islets of this kind has been a common event in the Azores, and many formed of firmer materials still exist to show their usual shape and character. Among them are, an island off Villa Franca, part of one joined to the land and forming a small bluff point at Rosto de Caen, a point N. of Mostyeros, and the moros or bluffs of Capellas and Ribeira Grande.
A.D. 1563. Between the 25th of June and the 7th of July a number of successive streams of lava issued from the sides of Monte Volcam, now known us the Serra da Agoa de Pao; and, on the latter date, the peak of the mounta{n sank, as that of th W. end is said to have done in 1445, and left in its place a deep valley nearly two miles long and one broad, now chiefly occupied by a lake whose surface is 1634 feet above the sea. The lavas of this eruption cover the western points of the mountains, extend to to the N.W. as far as Rabo de Peixe (where a solitary and prominent bluff marks their meeting with the sea), and on the north to Ribeira Grande. The flrst appearance of the Furnas hot-springs has been attributed to this convuls;on; but no account exists as to those of the Caldeiras, at the northern foot of the mountain.
A.D. 1591. Several severe shocks of earthqake ooourred beween the 26th of July and the l3th of August, when Villa Franca, after having been rebult to the westward of its former site, was again destroyed, and the sea broke high over the valley
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of Povosçao on the S.E. coast, and washed away a great part of the village
A.D. 1630. On the 2nd of September an explosion took place near the lake of the Furnas, unaccompanied by lava, when the neighbouring mountains were thlckly covered with pumice and and the lighter particles carried to Terceira, a distance of 90 miles. A circular hill of regular figure was formed on aspot in the centre of a plain surrounded by a low ridge, to which the name of "Lagoa Secca" has been given.
A.D. 1652. On the 10th of' October an eruption of lava broke out from the sides of the quiescent Pico do Fogo, on the N,E. of Rosto de Cao, forming the rocky slope over the sea-coast and some narrow tracts towards the N. shore. This was followed on the 19th by an eruption from a neighbouring hill, which took the same courses,
A.D. 1707. A torrent, attributed to the breaking of a water spout suddenly flowed through Ponta Delgada in the month of November, and caused great damage.
A.D. 1720. A succession of violent shocks of earthquakes in the towns and villages, and shook down large portions of rock from the shores and inland precipices; where indeed there numerous traces of catastrophes of this nature. A torrent ran down the sides of the Sette Cicades mountams and cut out a deep ravine near Mosteyros in its passage ta the sea.
A.D. 1744. On thc 5th of October a similar fall of water took place at the E. end, washing down the valleys of Povoaçao and Fayal da Leira and carrying away great parts of the two villages. The cause of such floods, even now not unknown in the Azores, has not been explained, nor has any record been left of the duration of the torrents and attendant circumstances, or the probable quantity of water discharged. With respect to Povoaçao it may be remarked thatthe peculiar shape of the valley, wide above and contracting with steep sides to a narrow outlet below, snd its proximity to the highest mountains, expose it to heavy falls of rain and a great accumulation of water in that lower part where the village is built; and if to this be added the fact that an inch of rain frequently falls within an hour at the level of the sea, it will appear that the destruction of the village may not have beencaused by any very extraordinary meteorological phenomena.
A.D. 1755. The earthquake that destroyed Lisbon was sensibly felt at St. Michael's, where the sea rose hlgh above its usual level and broke over the land, washing down the houses built on the lower parts af the coast.
A.D. 1806. A mass of rock, resting on argillaceous earth, slipped from its place in the precipitous sides of the valley of the Furnas leaving a chasm of more than 100 yards in diameter.
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A.D. 1811. During the summer a similar fall took place, so close to the last-named locality that the two existing chasms are only separated by a narrow ridge about l00 feet high. On the 13th of June an island was thrown up in the sea near Ginites, to which the name of the British man-of-war Sabrina was given by her commander, who witnessed the explosion. It was soon worn away by the sea, and is now only to be traced in a submarine cone 15 fathoms under the surface.
A.D. 1838. A land-slip occurred in the summer near the Furnas, opening a cavity more than 400 yards broad and 100 feet deep, in the thick deposit of pumice of those parts.
A.D. 1839. On the 5th of December a rise of the sea, like that of 1755, washed down several houses and parts of the cliffs on the S. coast, subsiding with the fall of the tide. It occurred at the time of spring tides, after a gale of wind from the N.W., which had veered to S.E. without moderating, the barometer standing at 28.82 inches. The change of wind acting in opposition to an acceleration of the great Atlantic current (whose course here is from the N.W.) at the time of full moon and under a di mi nution of atmospheric pressure, would probably produce an unusual tide; bnt it is remarkable that it was not observed at St. Mary's, nor did it extend to the westerly islands. At Ponta Delgada the rise was 101/2 feet above the high water mark of spring tides, whose ordinary rise is about 6 feet.
The geology of St. Michael's will be more easily illustrated by dividing the surface into 5 districts, each of which has its distinctive charactristics, although contiguous parts pass so confusedly into each other, that, strictly speaking, there is no line of demarcation between them. The first district, marked A in the map, is that of the Sette Cidades mountains; the second, B, that of the Serra Gorda and its succeeding line of peaks; the third, C, of the Serra da Agoa de Pao; the fourth, D, of the Furnas; and the fifth, E, of the Pico da Vara.
In the order of formation the last is probably the oldest;. in the fourth there has been no eruption of lava since the discovery of the island, although the surface must have been totally changed by the pumice of 1630; the present covering of a great part of the third has been formed since the middle of the sixteenth century; none of the older lavas appear in the second; while the oldest rocks are found in the first.
End of excerpt
The remaining, approximately 30 pages, have little revelence to active volcanism. The subject matter includes discussion of the geology of the older rocks, botany, weather, agriculture and the people of the island
