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February, 1878.
} (From the Canadian Naturalist, Vol. VIll. No. y.)

TRAVELLING NO. -^S

ON THE

SURFACE GEOLOGY OF THE PACIFIC SLOPE.

By Geor3k M. Dawson, D.S., Assoc. R. S. M., V. G. S.

When on my way to resume my geological duties in British
Columbia, in May last, I availed myself of the opportunity to
obtain a passing glimpse of Northern California, Oregon, and
Washington Territory ; leaving the Central Pacific Railway, for
thtit purpose, at Roseville Junction, near Sacramento, and travel-
ling northward, by train and stage coach, to the extremity of
Puget Sound, whence a steamer runs to Victoria, Vancouver
Island. The region was a very interesting one to me, constitu-
tin"' the southern extension of that which I have been enoaged
in studying in British Columbia, and characterized in the main
by the same great physical features. It is proposed now to give
the sub^^tance of a few notes taken by the way, on the superficial
deposits and general aspect of the country, connecting these with
facts already observed in British Columbia, some of which are
published in the reports of the Geological Survey, but treated of
at greater length in a memoir read before the Geological Society
of London, in June last. Dr. A. S. Packard, Jr., of the United
States Entomological Commission, passed through the saw ^

region, in August last, and has published some notes on the sur- V
face geology in the American Natxir<dlst for November, under
the title of " Glacial 31arks on the Pacific and Atlantic Coasts
Compared," To this article I shall again refer.

In descending the western slope of the Sierra Nevada, hard
clays, packed with boulders and stones, are seen in some cuttings
near Blue Canon Station (elevation, 4,(j93 feet) and at other
places, probably ns far down as Dutch Flat Station (3,305 feet).
These are doubtlepn old Uioraincs, due to the former glaciers of
the Sierra, which, according to the American geologists who
have examined this range, were at one time very extensive.

Leaving the rollinu' foot-hills, the train tjlides out on the wide
and generally fertile Sacramento Plain, in the midst of which the
city of the same name is situated. Near the base of the foot-
hills, large areas are covered with the so-called ' Hog Wallows,"
about which some discussion lately occurred in Xatnrv, it being
suggested by some that they were ccuuected with ancient ice
action. Mr. Gabb '■•- is no doubt right, however, in attributing
them to the accumulation of drifting sand and soil around clumps
of vegetation, whicli in some cases may have afterwards perished
from climatic or other causes, leaving only these peculiar hillocks
to mark their former positions. The banking up of sand and
soil about patches of cactus and siige i;-; seen freijuently in the
dry plains cast of the Eocky jMountains, as well as in Nevada,
to which Mr. Gabb refers.

Leaving the main line of railway at a right angle at Koseville,
and turning northward, one continues to travel over the same
Vt^ide, flat, or gently undulating plain of Central California,
bounded to the right by the snowy peaks of the Sierra, to the
left by the more rounded summits of the Coast Range. Soon
after leaving Maryville — an important town — a rugged and pic-
turesque group of hills, called the Butte Mountains, appear on
the left, some miles distant. They owe their outline apparently
to prolonged atmospheric waste, and are singularly different from
the dome-like summits of a glaciated country. At Reading,
about 120 miles north of Roseville, the railway comes to an end,-
and for 275 miles, the stage coach must carry us through a
country remarkably broken and tumultuous. Crossing the Sacra-
mento by a good ferry, soon after leaving Reading, a broad,

• Nature^ Vol. XVI, p. 183.

broken flat or plateau, with a height, according to the barometer,
of 7G(I feet is reached. Through this little rocky hills project,
and its general elevation is probably nearly that of the body oi'
water which must formerly have filled the central " Gulf of Culi-
! fornia'" for a prolonged period. The road continues to follow
the Sacramento Valley in a general way for some distance, cross-
\. ing first a considerable tributary, and then re-crossing the main
stream. The upper part of the river is very tortuous, and flows
in a deep, steep-sided valley, up which, as the road gains a con-
siderable elevation, distant views of the snow-clad cone of Mount
Shasta are, from time to time, obtained.

licaving the Sacramento where it turns westward, we climb,
by a small lateral valley, to the summit of a plateau^ with an
elevation of about li.oOO feet, and at Strawberry Valley find our-
selves apparently close to the base of Shasta. A little further on
volcanic rocks arc seen near the road, piled together in a way
suggesting the action of a glacier. Dr. Packard, who stayed
here to accomplish the ascent of the mountain, describes three
small glaciers v.hieh still remam near its summit, the upper four
thousand feet of which is covered with snow. These glaciers are
still engagea u piling up moraines, and have left others evi-
dencing their former extension. This mountain, at one time,
must have been an important centre of local glaciation, though
the phenomena of its vicinity are apparently quite distinct from
those of the almost universally glaciated north.

Shasta reaches an elevation, according to Prof. Whitney, of
4,442 feet, and, in its grand isolation, and the remarkable sym-
metry of its conical form, is very impressive.

Leaving Shasta, the road gradually descends into the broad
valley of a tributary of the Klamath River, and passing through
a wide gap in a range of hills, Yreka — once an important centre
of alluvial gold mining — is reached. About fourteen miles from
[\^ Yreka, a flat resembling a terrace was observed skirting one of
the hills, with an estimated elevation of 250 feet above the flat-
bottomed valley, or about 2,775 feet above the sea.

Beyond Yreka the Klamath River is crossed, and on the line
between California and Oregon the Siskiyou Range is slowly
ascended, the summit on the road b^mg, by my aneroid, 4,500
feet in height, and the actual descent from this place to the
.stage stable on its western base being nearly 3,000 feet.

After passing Jacksonville, situated on a branch of the Rogue

River, in a small, but fertile aid beautiful valley, the main
stream of the Rogue River is crossed by a good bridge. Between
this river and the South Umpqua, is a rugged and irregular coun-
try, in which steep-sided hills are huddled together, but in which
also several narrow but fertile valleys are concealed. Tuo Tlmp-
(|U!i once rcnchcd, is followed to Rosebuvg, whence a railway
stretches to Portland, near the junction of the Columbia and
Willamette rivers.

From the Sacramento River to this point all the streams crossed
flow westward to the coast, transverse to the proposed Oregon
and California Railway, the completion of which will be a very
diflScult matter. So far no traces of general glaciation, or de-
posits likp the northern drift, have been encountered. The hills
appear to have been subjected to prolonged sub-aerial weathering,
the rocks, when bared on their slopes, being generally soft and
decomposed at the surface. The soil covers the hills almost
uniformly from base to summit, except where the slopes are
remarkably steep ; and is probably in most instances a product
of waste of rock nearly in place. The bottoms of the valleys,
though occasionally flat, and suggesting the existence of former
lakes, or tliat the sea may at one time have flowed into them,
are gcnerelly characterized by broad coalescing fan-shaped deltas
of the lateral streams. The summits and higher slopes of the
hills are generally stony and gravelly, while the valleys have a
clayey or loamy soil, which graduates into the former irregularly
on the slopes. There is a remarkable absence of any well-marked
terraces or benches ; though, besides those already mentioned, •;
probable terrace was observed about thirteen miles above Rose-
burg, on the Umpqua, with an estimated elevation of 5 tO feet
above the sea. The general impression conveyed by the country
is, however, that there are no true terraces, which may arise
from the fact that the region has never been flooded, or if fl-^oded,
that sufl&cient available material (detritus) for the formation of
distinct terraces has not been at hand, or, lastly, on the supposi-
tion that the process of obliteration seen actively in progress in
the somewhat similarly circumstanced dry southern interior of
British Columbia, has here been so long continued as to remove
almost entirely tlie old water marks. The hills are everywhere
seamed with gullies which form the terminations of small valleys,
all of which are connected, uniting as they descend toward the
main stream. The almost complete absence of lakes or ponds, or

even hollows holding swamps, is very remarkable, and contrasts
strongly with the innumerable lake-basins of British Columbia.*
The water indeed seems never to rest from its sources in the
mountains till it reaches the sea. This is either due to the pro
longed action of the streams themselves in completely filling
rock-basins, if such there have been, and removing all other im-
pediments to their flow, or is the result of the original absence of
those great masses of material accumulated during u stage of the
glacial epoch, which in the north (as I hope elsewhere to show)
have in many places been mainly concerned, at a later period,
in forming lakes by the blocking of old valleys with detritus.
The local colouring of the soil, in its close resemblance to that of
the decomposed parts of the underlying rocks, indicating the
absence of foreign material, appears also to favour the latter
conclusion.

North of Koseburg the railway passes for some distance, with
heavy grades and sjiarp curves, through a generally hilly country,
crossing several branches of the Umpcjua, and then reaching
the upper part of the great and fertile Willamette Valley, which
runs northward to the Columbia, between the Cascade Mountains
with their flanking hills, and the lower ranges of the coast.

Prof. Thomas Condon, of the University of Oregon, has pub-
lished some account of the state of this country in the later geo-
logical times. This I regret not to have had the advantage of
reading ; but, as the paper is entitled " The Willamette Sound,"
it would seem to imply his belief in the former submergence of
this region. Prof. Le Conte indeed states thu.: Prof. Condon
has traced an old sea-margin from the coast up the Columbia
River to and beyond the Cascade Range. This he compares
with the sheet of nearly land-locked water which must have cov-
ered Central California at the same period, f

About two miles south of Creswell station, I noticed what
appeared from a distance to be a series of pretty distinct ter-
races, on a hill-side, at an estimated elevation of from 100 to

* This of couisi' applies to tlic region tiaversed, west of the Cascade
Moimtains, East of that range tlie Klaniatli antl otlier extensive
lakes appear on tlie map. These differ singularly in their form from
the long river-like lakes of British Columbia, and may possibly be
due to mountain elevation taking place more rapidly than the drain,
ing streams are able to lower their channels.

t Elements of Geology, 1878, p. 530.

200 r*ect above the road, which is here about 650 feet above the
sea. The valley is wide and ilat-bottonicd, gradually sloping
downward to the north, and (|uite different from any met with
on the line of route since leaving the plain " central California.
The soil is usually pale-coloured and often clayey, and north of
Engine, is seen in several places in cuttings to be underlain by
beds with large and small rounded stones. Beyond Albany, the
country is for some distance more undulating, and in many places
more or less perfectly bedded deposits of gravel and sand, with
occasional small boulders, occur. These much I'csemble some
varieties of modified drift, and are probably due neither to local
glaciers nor to the present or former streams, but to the transport
of material by ice during a general submergence. It is here that
we first meet with distinct traces of that invasion of the land
by the sea during a period of cold, which has been universal fur-
ther to the north.

The Willamette and Columbia Rivers, immediately be^ow
Portland, flow through a flat country, its general aspect, with
that of the rivers themselves and the vegetation of their banks,
being much like that of the Eraser below New Westminster. The
tide affects the Willamette up to Portland. Seven miles below
this place, on the left bank, very distinct terraces occur, with
elevations estimated by the eye as 100, 180, and 300 feet above
the river, the highest being about the general level of the surface
of the country here. In several other places more or less perfect
terraces appear, at various elevations, less than about 300 feet.

Leaving the banks of the Columbia at Kalama, our route con-
tinues northward between the two ranges before referred to.
The only portion of the Northern Pacific Railway yet built on
the West Coast, connects this place with Tacoma, 105 miles
distant and near the extremity of Puget Sound, which with a
ramifying form occupies the northern part of the same great
valley. The valley of the Cowlitz river is at first followed up
for some distance, several small streams which afterwards unite
and flow west through the Coast Range are then crossed, and in
a short distance water flowing northward to Puget Sound is
reached ; no strongly- marked watershed being observed. At
Olequa Station, twenty-eight miles from the Columbia, is a well
marked terrace or beach with an elevation of about 100 feet,*

* The elevation of places on this part of the route, though taken
by barometer, were checked at the sea level at both ends, and are
correct within a very few feet.

with a second about 80 feet higher. In following the Cowlitz,
banks in cuttings sometimes 50 feet in height, show tine, yellow-
ish horizontally-bedded sands. These are pretty hard, and arc
interbedded in places with thin and thick layers of gravel, com-
posed of water-rolled stones, some as large as the two fists. The
sandy drift exactly resembles that seen in low banks near the
water level on the Willamette and Columbia, but as we go north-
ward, and ascend, the gravelly layers continue to increase in im-
portance. Forty miles from the Columbia the railway passes
over a distinct and wide bench with an elevation of r];>7 feet, the
general level of the country — which is here nearly flat — being
about ;>80 feet. Gravel beds are abundant at Centreville (54 m.)
with u general elevation of about IGO feet. Here the rolled
gravel of the subsoil contains some small boulders up to ten
inches in diameter. At 05 miles from our initial point, eleva-
tion 230 feet, boulders two teet in diameter are first seen, and
a few miles further northward gravelly banks are found, of
rudely mingled coarse materials, including boulders up to three
and four feet in diameter, with overlying or interstratified layers
of fine yellowish sand. The country here becomes undulating,
with many low ridges and hillocks, and hegins to show small
ponds and swamps. A few miles south of Yelm Prairie (74 m.,
elevation 2!>5 feot), some ridges, in their composition resemble
the closely-packed gravel and boulder deposits of Spring Ridge
and B«!acon Hill near Victoria. From this point to Tacoma,
the county is generally flat or geutly undulating, and declines
gradually toward the head of the Sound, the superficial deposits
being in general not so coarse as those just described.

At Tacoma, the banks along the shore show a great thickness
of firm finely-bedded sandy and clayey deposits, which form the
substratum of the plateau above, but which I had not time to
examine. At Seattle — the centre of the coal mining industry —
about 30 miles northward on the east shore of the Sound, the
drift consists of sands, gravels and clays, without any apparent
regular sequence, but with occasional large and many small
boulders scattered through them. The sands are frequently
current-bedded, and in one place curiously contorted layers of
fine, hard, clayey sand, alternated with others nearly horizontal,
as though floating ice had from time to time disturbed the regu-
larity of the deposit. Some beds resemble in all respects true
boulder-clays, being thickly packed with large and small stones.

which lie ia all positious. These beds, however, seem to form it
part of the general series, and do not appertain specially to any
particular horizon. No clearly glaciated stones wore seen, though
from tl" chape uud appearance of many, it is probable that a
careful searca would bring such to light, as at Victoria. Fine
exposures of drift also occur at Port Townseud near the entrance
to the Sound, and elsewhere along its banks.

The drift deposits of Puget Sound, as a whole, very much
resemble those of the soutiiern part of Vancouver Island and
shores of the Strait of (jroorgia further north, which are described
in the paper above referred to. There is good evidence to show
that at one time a great glacier-sheet, fed botii from the main-
land and mountains of Vancouver Island, filled the whole Strait
of Georgia, and passing southward, overlapped the low south-
eastern corner, at least, of Vancouver Island. It would also
appear that when this glacier began to retreat, the sea was at a
level considerably higher than at present, and that as soon as the
heavily-glaciated rocks of the lowlands were uncovered, the drift
deposits — boulder clays, gravels and sands — were laid down on
them. These are found in some places near Victoria to include
marine shells. From a careful examination of the south-eastern
corner of Vancouver Island, my impression is that its gUiciation
though heavy, was not long continued, and it is probable tha*
in this case the front of the glacier did not at any time reach
far southward into the low co* ntry of the Sound, or westward
along the Strait of Fuca. Be this as it may, however^ it is
pretty evident that during the submergence above referred to,
the great valley, including the Sound, and country to the south,
of which the drift deposits have just been described, was a wide
strait ; along the margins of which local glaciers may have dis-
charged in some places, and in which sea currents, aided by
debris-bearing icebergs and coast-ice piled up the deposits now
found. It is probable that the same sheet of water passed yet
furt'ier southward, forming the Willamette Sound, of Condon, with
a wide opening to the open ocean by the valley of the Columbia
River. If the Strait of Fuca was not at this time encumbered
by glacier ice, the high Olympic mountains of the north-western
corner of Washington Territory must have formed a snowy sea-
washed island.

No great mass of glacier ice can have excavated the present
channels and water-ways of Puget Sound, as a glance at their

. .aii fe'i . 'Wi t crt t s i n TCa fa frtaB wpa wjtw i g^y /i'***'*

com plica tod form on any ijjoorl nup will s^how ; nor do the circuiu-
lotanccs allow them to bo accounted (or by the oxcivating action
of systeniM of local glaciers. Tf, however, the Strait of Gcor;^'ia
ice-sheet ever traversed the low eon now occupied by the

Sound, it may have planed ;ind levc ' to some extent.

Mr. George Gibbs has (h'scribed the passages and inlets of
Puget Sound as excavated in many places in drift deposits,
whicli appear not only to form their present banks, but to under-
lie their beds. (Jiuidod by the general form of the inlets, and
this descrijttioi). I ventured in a note on some of the more recent
changes in level of the coast of British (Columbia and adjacent
regions, printed in the i^iaixUnti Xnhfnr'ist for 1S77, to suggest
that they were cut out by rivers during a post-glacial elevation of
the land, and afterwards filled up by sea-water on its depres-
sion to the present level.

Though aware of the danger of generalising hastily lor a re-
s;ion which has not been thoroughly examined, I now venture to
again advance tliis idea with somewhat greater confidence. In
their outline on the map, these inlets resemble the fjords with
which the whole coast north of the forty ninth parallel is dissected,
but the latter penetrate into the heart of a rugged and moun-
tainous country, and though they may have been cleared of drift
material during a post-glacial elevation, have probably been ex-
cavated in the hard rock;? of the Coast Range of British Columbia
during a prolonged period in the later Tertiary, when the land
was at a high level. The canals of the Sound are excavated in a
low drift-encumbered country, based on soft Tertiary rocks, which,
owing to the thickness of later deposits are seldom. seen. The
average heigh of the surrounding drift-plateau is from 180 to
200 feet. The channels are deep — often over 100 fathoms — but
not uniformly so, is shallower bars cross them in many places
which would give rise to a series of great lakes if reelevation
should now occur. Here bars, like those so often found near
the e" "'ance of the fjords lo the north, are generally in observable
connection with their cause, in the opposition of tidal currents,
the shu ivcning of these currents as they enter wider channels,
or other circumstances bringing about the deposition of sus-
pended sediment. They are probably due to the most modern
period. In the wide flats surrounding the mouths of streams
and rivers, near the present water level, we have evidence of the
comparative permanence of the present relations of sea and land.

To recapitulate, a wido hollow deeply scored by rivers, probably
extended from the south of Vancouver Island to the Columbia,
in later Tertiary times. 'The northern part of this, now occupied
by Puget Sound, may or may not have been planed down by an
ice-shoet, but was deeply filled and levelled up with drift during
the glacial submergence and retreat of the great glaciers. Being
afterwards elevated to a height possibly 600 feet or more greater
than the present, streams again began to excavate their channels,
iruided no doubt in the first instance by such ill-defined longim-
diual hollows as the sea-currents, flowing north and south, had
before formed. This action continued long enough for the pro-
duction of deep and wide river valleys in the drift deposits, and
in some cases in the more prominent parts of the underlying
Tertiary rocks. Lastly, a resubsidence to the present stage hav-
ing occurred, the sea water filled the river valleys, of which the
gently-sloping sides soon became eroded at the water-line into
sea-cliffs, and tide flats were formed at the mouths of the streams
and wherever ditritus was abundant along the shores.

Diagrams illnHlrntinii stagca in the production ot thp In/rts <//?'/ P'tssagea

of I'll gel Sound.

No. I. Eroded (perhaps glaeier-planed) surface of the Tertiary rocks
(/') covered uniformly with drift material (<i) at tiie close
of the glacial epoch.

No. 2. Wide and deep valleys cut into the drift deposit: by streams.
Land standing at a greater elevation tlian at present.

No. 3. Valleys tilled by the sea owing to subsidence. Shore cliffs
and recent submarine deposits in course of formation.