EXTINCT VOLCANOES. 51 



give a milky appearance to the sea for some distance around. A 

 number of the masonry houses of Agana were destroyed, and those 

 left standing- were so badly injured as to be unfit for habitation. The 

 old bell tower of masonry near the church, built in 1669, was seamed 

 with large cracks. In the other towns of the island nearly all masonry 

 houses, churches, and rectories were ruined. The collier Justin was 

 sent the day after the disaster with an officer to the German island of 

 Saipan, 120 miles to the northward, to ascertain the damage done and 

 offer aid. They found no casualties, though the earthquake Had also 

 violently shaken the island. Fortunately the disaster occurred in the 

 daytime, as did the hurricane of 1890, and the casualties included but 

 one child killed and a few of the townspeople of Agana hurt. The 

 total cost of repairs to government buildings was estimated at $22,100 

 gold. 



A summary of the earthquake phenomena of 1902 is included in 

 Doctor Abbe's report, published in Terrestrial Magnetism and Atmos- 

 pheric Electricity, 1901, page 81. 



Extinct volcanoes. — All of the mountain peaks of Guam are 

 undoubtedly of volcanic origin. In some of them the outlines of the 

 craters may still be traced and the lava presents the same appearance 

 as in recent volcanoes.* Surrounding the bases of the mountains are 

 ancient coral reefs, the margins of which, in contact with the volcanic 

 products, have in many places been converted into crystalline lime- 

 stone, showing evidence of volcanic activity after the whole island 

 had been raised from the sea. The heights of the principal mountains 

 are approximately as follows: Santa Rosa 265 meters, Tiyan (Barri- 

 gada) 205 meters, Makahnag 215 meters, Chachao 320 meters, Tengho 

 310 meters, Ilicho (Humuyong-manglo) 390 meters, Sasalaguan (Hell 

 mountain), at the southern end of the island, 310 meters. 



Ancient coral reefs. — The entire northern portion of the island is 

 a raised coral platform penetrated in several places by the low volcanic 

 peaks already referred to. On the west side of the island between the 

 mesa and the sea several distinct flat terraces occur, showing succes- 

 sive upheavals. During the recent earthquakes the general level of 

 the whole island was raised. It would require only a very slight ele-' 

 vation to convert into dry land the very extensive reef flats along the 

 west coast which are covered at high tide by only a few feet of water. 

 The bottom between the shore and the barrier reef is perfectly level 

 and covered with very fine sand resembling flour in consistency. 



Minerals. — With the exception of thin layers of iron-ore, no metal- 

 yielding deposits occur on the island. An inferior lignite is found in 

 one or two places. There is also a volcanic rock called homon, which 

 is used for fire places, and a soft pale-green mineral called lauka which 



a This is especially true of Santa Rosa, in the northern part of the island. 



