484- SMITH. 



THE SULU ARCHIPELAGO. 



The Sulu Archipelago is practically unkno\vii from a geologic and 

 physiographic point of view, so that the information gained in this expedi- 

 tion, although meager, is at least new. 



Dr. Becker refers in four lines of liis report to rocks on Marongas Island just 

 across from the town of Jolo. Other than this there are no geological notes. 

 Some eruptions of the year 1614 are described by the resident Jesuits but only in 

 a crude way. It has been known for a long time from the reports of ship captains 

 and travelers that the archipelago is largely volcanic. 



This great group of islands extends for 335 kilometers southwest of Zamboanga. 

 It is about 120 kilometers wide and contains hundreds of islands and rocky shoals. 

 The most considerable of the islands are Basilan, Sulu, Siasi, and Tawi-Tawi and 

 although Basilan is the largest, Sulu is of far greater commercial and historic 

 interest. 



The water is nowhere of great depth within the confines of this ar- 

 chipelago, but it is separated both from Borneo and Mindanao by deep 

 straits. To reconstruct a large island out of this swarm of small ones 

 which may or may not have formed a continuous bridge from Borneo 

 to Zamboanga, and which would since have been disrupted and partly sub- 

 merged, is not a great tax upon the imagination. The evidence we 

 have points in this direction. 



The Sulu group, like so many other oceanic islands, is either of vol- 

 canic or coral formation. I saw very little sedimentary material on 

 any of the islands and where any such was exposed, it was usually at a 

 point where erosion had removed the lava capping. I do not know of 

 any marked volcanic activity in the Sulu Archipelago at the present time, 

 although hot sj)rings in old craters are reported on Cagayan Sulu. 

 I have also been informed that there are hot springs and solfataras at 

 Si'it Lake on Sulu. This lake occupies an old crater. I have visited 

 neither of these places. 



An eruption at a point near Jolo, not named, is reported to have 

 occurred on January 4, 164-1.^^ As there is some confusion of names 

 in this report I do not attach much importance to the account. As 

 far as I can learn, no accurate scientific notes were taken at the time. 



The only remaining reference I find regarding the geography or 

 geology of the Sulu Archipelago is a note by Becker :^" 



"In the Jolo Archipelago, the charts indicate several well-developed atolls, 

 such as Simonul Island (latitude 4° 52', longitude 119° 50'), as well as several in 

 the Tapul group (latitude 5° 30'). The charts of this region also show innumer- 

 able coral reefs, which are bare at low tide and must therefore have been uplifted." 



" Baranera, Francisco X. : Compendio de geograffa de las Islas Filipinas, 

 jMarianas, Jolo y Carolinas. 3r ed. Manila, 1892. 

 " Geology of the Philippine Islands, 562. 



