Bonners Ferry herald. [volume] (Bonners Ferry, Idaho) 1904-current, 1922-07-13
INTERESTING GEOLOGICAL FACTS
PERTAINING TO NORTHERN IDAHO
And BOUNDARY COUNTY
GEOLOGICAL SURVEY OF BOUNDARY COUNTY REVEALS HAPPENINGS
OF MANY CENTURIES AGO, RESULTING IN FORMATION OF
MOUNTAINS, VALLEYS, LAKES, DEPOSITS OF
VARIOUS FORMS OF MINERALS

tain living glaciers at heights OF
\ 5000 feet This range contains only
two relatively small areas of granite
Purcell Range
That part of this range which lies
in Idaho is defined by the flow of the
kootenai river. All the mountains Ia
the east and northeast of Bonners
Ferry belong to this photographic
province. This range in turn is
divided by the Moyie and Yaak rivers
flowing into the Kootenai valley
Like the Cabinet Range this area was
originally high plateau, and now
rugged and irregular due to the same
irresistible erosion agencies. The
peaks are of nearly the same height
and none are conspicuous. The rocks
are all of the Belt Series and their
resistance has permitted heights OF
1900 feet to be maintained ON this
lofty dissected plateau.
The Purcell Trench
This great depression extending for
hundreds of miles in north and
south direction serves to cut the great
Rocky Mountain system in twain and
its origin lies in some gigantic break
in this part of the earth's crust. soon
after the deposition of the vast Belt
sediments. 1t extends from Canada
south to Bonners Ferry and to lake
Occur d'Alene by way of lake Pend
dOreille and Spokane river. 1t is
occupied by the Kootenai river north
OF Bonners Ferry and averages nearly
miles in width being bordered by a
mountain wall on either side AT
places south of the town it reaches a
width of miles. Most of it is covered
by gravels brought from the noun
tains which guard it by age old rivers
and more recent glaciers and ice
sheets. Many of the tributary CANYONS
cut deep into the enfiladind ranges
and contain scenic lakes.
kOOtenai Valley
kootenai valley although formed bv
a great fault in the manner of Purcell
Trench differs in most other aspects.
In the Idaho region it boasts
narrow valley bordered by precipi-
tous cliffs and lofty peaks, through
which the turbulent waters of the
kootenai tumble swiftly toward Bon
ers Ferry, and Purcell Trench
Several hundred feet above the river
lies broad terrace noticeable on
either side of the stream. This marks
the bed of the imposing glacier that
once dominated this drainage line
This terrace is fairly uniform. since
where there were eminences the pom
derously moving glacier sheared them
away, and with the same material
supplemented by its ever present load
nlled in equally large depressions.
Consequently this terrace is made nm
of rock shelves secured smooth. ac-
cumulations of gravels, and variouslv
sized rock fragments.
The industrious river with it's
plentifully supplied tools of water
ana abrasive sediments has almost
equalled the glaciers excavation by
trenching the rivers canyon to its
present level. Valleys developed by
tributaries to the glaciers, have as
consequence been left high on the
canyon side little below the terrace
level These are known as Hanging
valleys"
The Hope and Lenia Faults are two
great dislocations of the region that
plainly show their effect on the
country The latter fault extends
from~the Idaho line along the course
OF the Kootenai river to the mouth
OF the Moyie river and was the de-
Gliding factor that influenced the great
glacier to choose that course of its
path. The great valley of the glacier
in turn offered a ready made course
for the Kootenai river of our own day
At Lenia which is on the fault
line, the rocks on the two sides of the
river dip in opposite directions. The
Deds In the river bottom to the west
OF the fault are the same as the ones
on the mountain tops to the east. The
displacement of this great break was
at least three vertical miles, and at |
one time an escarpment of great
height must have existed on the west
side. Millions of years of exnosure
70 the incessant cutting power of
water and ice have carved it down to
its present appearance.
The Hope Fault forming the north
ern boundary of lake Pend d'Orielle
from Standpoint to near Clark Fork
presents a great escarpment which
has been maintained by the aid of the
glacier that helped scour out the lake
basin of that body of water. The
original displacement here was prob
ably in excess of 10000 vertical feet
Lakes
All the lakes of the region owe their
existence to some direct influence of
the glaciers which have been de-
scribed previously as coming down
from the north during the invasions
of the great ice sheets.
The two larger lakes of north Idaho,
Occur dAlene and Pend dgOrielle, |
were originally river valleys follow
ing the riffs developed by the gigantic
faults. The invading glaciers. choos-
ing the lines of least resistance where
possible, secured out these depressions
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