66 Adventures in Scenery 



and sediments from land somewhere were being carried in by 

 streams and deposited, followed by periods of elevation when 

 these sediments became dry land and were in turn subject to 

 erosion, represent a long series of chapters of geologic history. 

 "Unconformity" means that what had been land was again 

 below sea level, and sediments were again deposited on the 

 eroded surface. How long the period of erosion it may be im- 

 possible to tell, but the sediments deposited on the uneven sur- 

 face do not "conform" to the eroded rocks. Thus there is an 

 "unconformity" in the series of rocks as they are observed in 

 after ages. The unconformity represents a lost interval, as no 

 record was preserved in the rocks of what happened on the sub- 

 merged land surface while it was being eroded. Periods of 

 elevation were so long that thousands of feet of sediments were 

 removed by erosion, and beds thousands of feet in thickness were 

 laid down. Can the mind conceive of such periods of time? 

 Only by comparison. Seven sedimentary formations, and five 

 unconformities, and in the Santa Cruz region 14 formations 

 and nine disturbances, have been recognized where changes of 

 land and sea were so great that unconformities or breaks in the 

 sedimentary record occurred. 



Early History of the Coast Ranges 



These great and profound events in the region of the Coast 

 Ranges occurred after middle geologic time, that is, they are 

 post- Jurassic events. (See Geological Table, Fig. 17.) The 

 long periods of the Palaeozoic era preceded. Before Palaeozoic 

 was the immensely long primeval era, the Archaean. It has been 

 estimated by competent geologists that the time preceding 

 Cambrian (the earliest period of the Palaeozoic, and the oldest 

 in which a definite fossil fauna has been found) was longer than 

 all geologic time since. We may therefore accept with some 

 assurance the conclusion that time in geology is long! 



The earliest geologic event of which there is any clear record 

 in the region of the Coast Ranges of California is the invasion 



