REPORT OF THE GEOLOGY OF THE PHILIPPINE ISLANDS  (Google eBook)

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Page 81 - Mindanao were represented by groups of islets. Observations appear to suggest that the Agno beds represent the basal conglomerate formed at this subsidence. A slow rise began again during the later Miocene, and may have continued to the present day without inversion, yet the actual distribution of living forms is such as to give some grounds for believing that, at some intermediate period, the islands were a little higher than they now are, but sank again only to rise afresh. The diorites and associated...
Page 82 - Cebu are all Miocene, the earlier andesitic rocks, at least, date back nearly to the great upheaval. Among these rocks, also, there is sometimes a tendency for the basalts to follow the andesites, but the one dacite found at Corregidor is later than the andesites of that island. The relation of the trachytes to the andesites is not certain, but the sanidine rock is probably the earlier.
Page 45 - Mayón, or the volcano of Albay, is, next to Taal, the most famous Philippine volcano. It is possibly the most symmetrically beautiful volcanic cone in the world, and at times its crater is almost infinitesimal, so that the meridional curve of the cone is continuous almost to the axis. The height has been variously determined, and appears to change with each eruption. Since the crater always remains small, the height should tend to increase, but the determinations are probably not sharp enough to...
Page 81 - Summarizing the foregoing facts and inferences, it would seem that the geological history of the Philippines is something as follows: From early Paleozoic times onward an archipelago has usually marked the position of these islands. Prior to the Eocene nothing definite is known of them, but further investigation will very likely disclose Paleozoic and Mesozoic strata there, as in the Sunda and the Banda islands. During the Eocene it is probable that the lignitic series of...
Page 82 - Among these rocks also there is sometimes a tendency for the basalts to follow the andesites, but the one dacite found at Corregidor is later than the andesites of that island. The relation of the trachytes to the andesites is not certain, but the sanidine rock is probably the earlier. A very large part of the neovolcanic ejeeta has fallen into water and been rearranged as tuffaceous plains.
Page 72 - Eocene, which consist of unfossiliferous strata underlying Stage a; but the absence in the region of Benguet of the Cebuan lignitic series and the character of the organic remains appear to indicate that this portion of Luzon was above water during Eocene time/' It may be possible that the tentative suggestion of this correlation may be later worked out, as it has happened that lately a small seam of lignite has been discovered on the Benguet road in this region. As it was not seen, its relations...
Page 81 - Eocene movement which so profoundly modified Asia and Europe. It must have brought about temporary continuity of land area between Borneo and Luzon. Somewhere about the middle of the Miocene the country sank to a low level. Many of the present islands must then have been far below water, while Luzon and Mindanao were represented by groups of islets. Observations appear to suggest that the Agno beds represent the basal conglomerate formed at this subsidence. A slow rise began again during the later...
Page 91 - Gold is found in moderate quantities nearly all over the Island of Luzon, but more particularly and under conditions favorable for exploitation in the following townships and districts, proceeding from north to south: 1. Abra Province. 2. Village named Fidelisan, Bontoc Province. 3. Village named Suyuc, Lepanto Province.
Page 48 - ... 1,900 meters (6,233 feet) and the east-west diameter 2,300 meters (7,546 feet). The edge of this crater is somewhat irregular, but is nowhere broken through, its highest point standing at only 320 meters (1,050 feet) above sea level and its lowest at 130 meters (426 feet). It is said that Coshima, in Japan, is the only other volcano of similarly low altitude. Within the rim are two hot pools, known, respectively, as the yellow and the green lake, and a little active cone about 50 feet in height,...
Page 43 - Passage, Canlaon is a very impressive spectacle, for, in addition to the picturesque form of the cone, steam is always pouring out from at least two vents at the summit. No violent eruptions are remembered, but ash has been ejected from time to time. The last considerable ash fall occurred, as I was informed at San Carlos, in July, 1893. There was also an eruption in 1866.* Andesite is the prevailing rock of this region, as shown by the stream pebbles, and I suppose Canlaon andesitic.

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