St. Charles City Republican intelligencer. [volume] (St. Charles City [Charles City], Iowa) 1857-1861, 1859-07-21
GEOLOGY OF IOWA.
EXTRACTS FROM HALLS GEOLOGICAL SURVEY

lhc bluffS form, next To the 'pralrieS,
the most marked popularity of the
surface throughout the Northwest.
Over a great portion of the region
south and west of the great lakes, the
rivers flow in valleys, which are some
times so narrow as to become almost
ravines, and which appear to have been
eroded by the action of water, their
depth and breadth increasing with the
magnitude of the stream and its dis
tance from its source. These valleys
do not connect with the uplands by
gentle rise, or sloping hillsides, but by
PERCEPTIONS, sharply defined and,
usually, rocky ascents or bluffs. These
are often perpendicular, or nearly so,
for a considerable portion of their
height, when the rock is exposed, as
is almost always the case if the val
ley has any considerable depth. More
usually, however, Il steep talus OF
rock and rocky fragments, thinly COW
cred with soil, is crowned on the sum
NIT with a crest of PERCEPTIONS rock,
worn in variety of fantastic forms,
and cut by the deep ravincs of the
streams coming in one side or the 9th
cr, giving origin to the peculiar and
picturesque scenery Of the northwest,
which is so we'll known to travellers
and tourists upon the Upper Missis-
sippi.
The height of the river bluffs is va
riable, depending, as before remarked,
partly Oh the size of the stream and
the distance from its source, and vary
ing, also, from other and more gene
raj causes, in various districts OF the
State. The streams usually take
their rise in small dcpressions of the
high prairics, hardly to be noticed as
being below the general level of the
region as their course continues, their
beds gradually sink, and soon become
bordered at points with steep banks
of detrtal material and then with ver-
tical walls of rock, which increases
in height, pretty regularly, to the en-
trance of the tributary into the main
valley. In the northeastern corner
of the State, however, the valleys are
deeper and more precipitous than in
any other portion of the State yet ex-
| amincd by us, and there is gradual
diminution in their depth towards the
south. Thus, on the Mississippi, III
the neighborhood of Prairie du Chen
the general level of the high prairie
is over 400 feet above the river, and
there is an almost vertical rise III the
bluffs of about 800 feet At Dubuque
the edge of the bluff, which ascends
steeply from the river, is from 200 t.
| 2l0 feet in elevation and there Is i
! farther immediate elevation of about
80 to 100 feet in addition, making the
whole height from $50 to 800 feet. AT
| Burlington, the bluffs are from l20 to
l40 feet high, a steep talus OF from
l00'to l20 feet being crowned by a
perpendicular wall of from l5 to 81
feet in height. The tributaries of tn,
Mississippi in the northeastern cornc
of the State have all cut deeply int,
the rocks, in the lower part of thci
course. Thus, the Upper Iowa is Dor
dered by bluffs 500 feet high as ia
up as New Galcna at Decorah thei
altitude is from l30 to l4O feet, bu
they are neither as steep nor as sharp
" defined. La the southern part o
the State the streams rarely cXhlhi
sections of as much as 100 feet, whcr,
they have worn their channels th'
deepest.
The prairie region of the west oc
cupies vast extent OF country, cN
tending over the eastern part OF Ohio
Indiana, the southern portion OF Mich
gan, the southern part of Wisconsin
nearly the whole of the States Of Ill
nois and Iowa, and the northern pol
+ ton of Missouri, and gradually pass
ing, in the Territories Of Kansas an
Nebraska, into the plains, or the ari
and desert region which lies at tn
base of the Rocky Mountains. Thi
, passage takes place in the region be
, tween the parallels Of 90 and 100
west of which belt the country be
comes too barren to bc inhabited an
worthless for cultivation. The pa
r sage from the heavily wooded regio
= of the North and East into the tire,
less plains of the West is gradu;
one, and the disappearance OF the III
derwood and the predominance OF Goa
5 openings" OF groves of oak and otht
5 forest trees, not crowded together, bl
scattered over the surface at a consi,
cradle distance from one another, wit
D out any low shrubs or underbrush b.
!. tween them, is the characteristic {
V the border of the prairie region. 1
h one coming from the dense thickets (
low aud tangled shrubs which choE
; the forests of the North, and rendt
S travelling through them difficult, eve
:. to the pedestrian, the open woods
h the Northwest offer striking CO
, trast to that which has been left b
hind, and forms natural introdu
> ton to the grassy plains or prairies.
The elevation of the prairie regiC
l. above the level of the sea gradual
q increases from the east to the Yves
The lower part of Illinois varies fro
100 to $50 feet above the river
l. Cairo, or 400 to $50 feet above Il
<, sea level. In the central portion
d the State the dwellings along the lii
-, of the Illinois Central railroad int
" cate an average elevation Of from s.
Is to $50 feet, which increases towar
r the northern boundary to 500 or 81
s feet above the sea. Some of {
" highest swells of the prairie attain
!, elevation of nearly 1000 feet. L
H. more elevated portions Of Southe
l. Wisconsin are about 100 feet abo
y tide-water. The region from the NJ
b. sissippi westward is gradually ;
o cending plain as far as the very ba
of the Rocky Mountains. Within t
III limits of Iowa the table-land, alol
rs the watershed between the streal
y flowing into the Mississippi and 7
Missouri, the "lateau du Coteau d
Prairies of Nicollctt, attains the
titude of from 400 to 1900 feet abo
the sea and to the west Of the Nj
!" souri, the ascent still continues, t
soil being more and more arid, un