532 HISTORY OF PASADENA. 



1 89 1, he contributed to the Atlayitic Monthly an able article on " Prehistoric 

 Man on the Pacific Coast ; ' ' and from this I quote the following pertinent 

 passages : 



"The changes which have taken place since man became an inhabitant 

 upon the Pacific coast appear enormous" and "are referred for their origin 

 to the climatic conditions accompanying the great ice age of North America. ' ' 

 * * "The ice age was one of great precipitation all over North America, 

 in which the rainfall and snowfall were far larger than at the present time, 

 and in which evaporation was far less than now." 



"At last there came upon the inhabitants of that region, both man and 

 beast, the added disturbances of the vast volcanic eruptions which have 

 covered so much of the surface with indestructible basalt ; though we are 

 not compelled to suppose in California any great direct destruction of plants 

 and animals by these volcanic outbursts. The extinction of species was due 

 rather to the general disturbances of the conditions of life brought about by 

 this new element in the problem. ^ * There can be no question that 

 these enormous eruptions of basalt are correlated with the equally surprising 

 facts connected with the glacial period, and, as we have seen, these two 

 periods were doubtless closely contemporaneous in California." 



"The region from the Rocky Mountains to the Pacific coast belongs to 

 the later geological eras, and has been subject to comparatively later eleva- 

 tion. The Rocky and Sierra Nevada mountains doubtless mark lines of 

 present weakness in the earth's crust. It is by elevations along such lines 

 of weakness that the gradually contracting sphere of the earth gets relief. 

 Now, during the glacial period an area in North America of about 4,000,000 

 square miles, extending northward from a line connecting New York and 

 St. Louis, was covered with ice to an average depth of probably three-quar- 

 ters of a mile, making, we may suppose, 3,000,000 cubic miles of ice. This 

 ice represents the excess of the snowfall above the melting power of the 

 sun over that region, and it was all first lifted up in vapor from the ocean. 

 To produce a glacial mass of such dimensions, water enough was taken from 

 the ocean to lower its level, the world over, one hundred feet. Thus we 

 have the ocean beds relieved from an enormous amount of pressure, and the 

 same amount concentrated upon the northern and central portions of the 

 continent. Thus we have a cause which w^ould, by its local pressure alone, 

 lay open immense fissures along the lines of weakness west of the Rocky 

 Mountains, and force out of them the liquid streams of lava which have 

 produced such significant changes upon the Pacific coa.st. ' ' 



It was in connection with the great climatic disturbances above described 

 by Prof. Wright that the sub-glacial floods poured down from Millard 

 canyon, and the upper Arroyo Seco, and the La Canyada valley, bursting 

 over or through the barrier ledges and previous deposits which held in 

 place the four terrace lakes before mentioned, within Pasadenaland. Of 

 course this did not all occurr at once, but the process went on both regularly 

 and spasmodically for centuries, before the Arroyo Seco was cut down to its 

 present condition, after some earthquake tremor had started a seam through 

 the foothills where the lower Arroyo now takes its course. This Arroyo 

 gorge from La Canyada down is in a geological sense comparatively recent, 

 and was probably not formed at all until long after our ancient townsite 



