Page:Washington, A Guide to the Evergreen State.djvu/44

 average 61° F. with a daily average maximum of 74°. Yearly snowfall varies widely, averaging less than 13 inches at Seattle, while Snoqualmie Pass has had 400.

Puget Sound area crop seasons average 207 days, diminishing to 185 in the valleys south. First frosts usually occur in November, and the last frosts in March. Wind velocities vary from a yearly average of greater than 12 miles on the coast, with occasional seasonal bursts of hurricane intensity, to 6 miles per hour in the interior.

Washington is a region where nature, on the whole, has been kind, barring it from catastrophic earthquakes, cyclones, drouths, and extensive floods, and endowing it with a climate assumed by scientists to be highly favorable for physical and mental exertion.

When western Washington experienced the most severe earthquake in its recent history in November 1939, the relevance of geologic history to present-day life was made dramatically clear. During the period of gigantic mountain building millions of years ago, the ancient peak Mount Si was covered by the Cascades, but never has there been real conformity between the hard primeval rock and the younger volcanic formation. The younger rock slips from time to time, as some earth movement takes place, and the resultant tremendous jar is felt through- out the region. (This explanation may be superseded by another differing in detail, but the general theory is substantially correct, according to authorities.)

In the Proterozoic era, the earliest of the four geologic divisions of time, long before the Cascades had risen, an embayment of the primeval sea covered most of the Pacific Northwest region. The Blue Mountains, in the extreme southeastern corner of the present State, have been described by some geologists as a rocky promontory extending into this arm of the sea. Some 300 or more miles to the west of the old coastline, south from what is now Washington, lay an island, or islands, the existence of which has led to the erroneous belief that another continent lay to the west of this one in prehistoric ages.

After hundreds of millions of years, with alternating periods of submersion and dry land, the region was invaded by the sea from the north, in the Paleozoic era. The depositing of silt from adjacent land areas and other natural processes resulted in the filling up of the original embayment to a maximum depth of 30,000 feet. Present deposits of quartz, slate, marble, and schist represent these ancient ones, but greatly