NATURAL MOUNDS 



MARIUS R. CAMPBELL! 



Recently the subject of natural mounds has attracted unusual 

 attention, and a number of persons have described their occurrence 

 and attempted an explanation of their origin. 



What are here designated as natural mounds are low, broad 

 mounds, varying from lo to 140 feet in diameter, and from, a few 

 inches to 5 or 6 feet in height. They are wonderfully symmetrical, 



Fig. I. — Group of natural mounds on old sea terrace back of San Diego, Cal. 



both in plan and in elevation, and generally they closely approach 

 a circle in outhne, but in places they are slightly elliptical, and where 

 such is the case the major axes of all mounds in the vicinity have 

 a common direction. 



Figure i is reproduced from a photograph of a group of slightly 

 elliptical mounds occurring on the old sea terrace back of San Diego, 

 Cal., at an altitude of about 380 feet. Frequently the mounds are 

 closely bunched, as shown in the figure, but they occur also singly 

 and in small groups. 



According to the descriptions of various writers, the composition 

 of the mounds vary considerably, probably being affected by the 



I Published by permission of the Director of the U. S. Geological Survey. 



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