The Rocks of the John Day Valley [pp. 393-398]

THE
OVERLAND MONTHLY
DEVOTED TO
THE DEVELOPMfENT OF THE COUNTRY.
VOL. 6.-MAY, I87i.-No. 5.
THE ROCKS OF THE JOHN DAY VALLEY.
N the controversies of the day on
the Origin of Species, any record
of the past as authoritative as that of a
good geological field, covering an extensive range, and filled with minute details of events, can hardly fail to be instructive. The basin of the Columbia
River with its tributaries offers such a
history to the world, at once continuous
and authoritative, reaching, in its field
of operations, from the Rocky Mountains to the Pacific Ocean; and, in the
time it covers, from the Cretaceous period to the Recent. It covers even the
laying of the foundations of the country,
and defines the narrow strips of land
that first emerged from the ocean to become the frame-work of the great mountain-chains. As the elevation and extent
of the land increased, the ocean water
that first occupied the depressions between was displaced, and fresh water
took its place, brought there by the now
greatly increased flow from the land.
Henceforth history written by the ocean
ceased; history written by lakes and
rivers commenced, in the storing away
of specimens of tree, and beast, and
bird, and their effectual preservation as
material facts in an unerring record.
The sea, thus excluded, never returned
to the region east of the Cascade Mountains. A vast lake-system took its place,
and began at once to make, as well as to
write, its own history.
There are many residents of the Pacific Slope who will remember having
journeyed from The Dalles, on the Columbia River, to Cafion City, among the
Blue Mountains. For sixty miles or
more the road passes over volcanic materials, which have drifted there from
the Cascade Range. Twenty miles farther, and this outflow thins out into a
mere capping of basalt on the hill-tops.
The hills themselves, and the foundations on which they stand, are here found
to be sedimentary rock, wonderfully filled with the abundant records of former
animal and vegetable life. Oldest of all
in sight is the old ocean-bed of the Cretaceous period, with its teeming thousands of marine shells, as perfect to-day
in their rocky bed as those of our recent
Entered according to Act of Congress, in the year x870, by JOHN H. CARMANY, in the Office of the
Vr.. VT'- _.{6. Librarian of Congress, at Washington.