THE MAEIANAS. 



275 



Fig. 



121. — Mariana Archipelago. 

 Scale 1 : 8,000.000. 



of whose cones rise many hundred feet above the sea, while others, failing to reach 



the surface serve as a foundation for a cro^vn of coralline limestones rising above 



the surrounding waters. The chain stretches north and south a total distance of 



about 600 miles, and the seventeen islands with their islets and reefs have a 



collective area, estimated by Agius at 



little more than 400, and by Behm and 



Wagner at scarcely 560 square miles. 



Guam, or Guahan, the largest island, 



comprising nearly half the extent of the 



Avhole group, is continued southwards 



by the Rosa Bank, which lies on the 



northern edge of the deepest cavity in 



this part of the Pacific (2,475 fathoms). 



North-east of this abyss the soundings 



of the Challenger show everywhere depths 



—A /a /774? ^61 /7 



u^usr 



^n6L éa^^ a n- 



of over 1,500 fathoms. 



Considered as a range of half- sub- 

 merged mountains the Marianas begin 

 with a few basalt and tufa crests, which 

 in Guam attain a height of from 1,300 to 

 1,600 feet, dominating the grassy or 

 wooded plateaux, the sandy or argillaceous 

 plains, and steep coastline of this pictur- 

 esque island. Northwards the chain, 

 interrupted at first by a channel thirty 

 miles wide, reappears in Mount Tempin- 

 gan and the rock-bound island of Rota or 

 Sarpan. Then follow Aguijan ; the charm- 

 ing Tinian with its gently undulating 

 hills ; Saypan with two extinct volcanoes 

 at its northern extremity ; Alamagan, 

 whose smoking crater is probably the 

 culminating point of- the archipelago 

 (2,320 feet) ; Pagan, composed of two 

 mountainous islands united at the base, 

 bearing two active and one quiescent vol- 

 cano ; Agrigan with an extinct cone ; and 

 Assumption (2,100 feet), whose fissured 

 flanks still emit vapours. The Uraccas, 

 or Mangas, near the northern extremity 



of the chain, seem, like the Dedica islets off the north coast of Luzon, to be the 

 remains of a circuit of marine craters, while Farallon dos Parajos, terminating the 

 whole system, is a still active volcano 1,300 feet high. Altogether the chain 

 appears to contain six not yet extinct cones. 



Depths. 



P 



Oto 



1,000 



Fathoms. 



1,000 to 

 2,000 

 Fathoms. 



2,000 to 



3,000 

 Fathoms. 



3.000 

 Fathoms 

 and upwards. 



120 Miles. 



