VOLCANIC CRATERS IN THE SOUTHWEST 723 



the explosive action of local vulcanism. If they were located anywhere but 

 in an arid region, they would always be filled with water. Now they are 

 either dry or are salt lakes in the last stage of desiccation. 



Crater salt-lake lies between 200 and 300 feet below the rim. It is excavated 

 from sandstones of Cretaceous age, while Coon butte crater is hollowed out of 

 Carboniferous limestones. Crater salt-lake is bordered all around by a broad 

 zone of unconsolidated pyroclastic material. From one side also extends a 

 narrow basalt flow. 



In the region are other stages of volcano building. There are low volcanic 

 cones in which the amount of fine dry material blown out has nearly covered 

 up all evidences of disturbances in the indurated strata beneath. Some craters 

 of similar cones have also lava flows miles in length. The single basaltic 

 stream from Maxwell cone, north of Las Vegas, extends a distance of 30 

 miles. From a small crater in the bolson plain lying between the Jicarilla 

 and Oscura mountains, in central New Mexico, a lava stream 2 to 4 miles 

 wide follows the central depression of the plain a distance of over 50 miles. 



The most majestic of these dry eruptions is mount Capulin, in northeastern 

 New Mexico (see plate 81). This is a lofty cinder cone 2,500 feet high, with a 

 crater half a mile across and 500 feet deep. Plate 82 is a view taken from one 

 side of the rim, and plate 83 a near view of the central plug of lava at the 

 bottom of the crater. A view of other cones in the vicinity as seen from the 

 top of the mountain and of the lava fields is shown in plate 84. 



Mount Capulin is far more imposing than Vesuvius. In the fine, light, 

 scoriaceous material of which it is mainly composed one sinks knee-deep in 

 climbing its steep sides. On the southwest side the crater wall is breached 

 and the heavy lava flow extends for many miles around. In the bottom of 

 the crater the old plug of solid lava is well displayed. 



Mount Capulin is as fresh in appearance today as is Vesuvius. There is a 

 local tradition that the mountain was in action as late as 1812. If this is so, 

 it is the latest volcanic eruption in the United States. The twin-cratered 

 Sierra Grande, 15 miles to the east of mount Capulin and rising much higher 

 (11,000 feet above tide), is reported to still show signs of dying activity, and 

 the heat in the craters is sufficient to melt the falling snow. 



From Coon butte, through Crater salt-lake and a host of nameless craters, 

 to mount Capulin are represented all the stages of dry explosive action of 

 volcanic forces. Coon butte stands at one extreme, mount Capulin at the other. 

 In Coon butte we find the first stage of volcano construction — a stage rarely 

 met with. Crater salt-lake represents a more advanced stage and is equally 

 unique. 



The two following papers, which were presented under the title 

 Hawaiian Notes, are printed as pages 469-496 of this volume. 



GEOLOGY OF DIAMOND HEAD, OAHU 

 BY C. H. HITCHCOCK 

 MO HOKE A C. 1 L DE R, I 

 BY C. H. HITCHCOCK 



