The mirror. (Stillwater, Minn.) 1894-1925, 1905-06-08

Paper Read Before the Cnautauqua Circle.
IN NO part of the world are the
manifestations of the two great
forces of nature-water and fire
more strikingly shown than IN that
region known as the Great Northwest
of the United States. A trip through
portion of this area, some few years
ago, in the company of government
surveying party, was highly instructive
as we'll as particularly impressive, so
that it has led not only to the con-
tinued study of the subject, but to the
choosing as theme for today's dis
course, the geological formation of this
section.
Two phenomena that are of popular
as we'll as striking interest in the world
of geology are glaciers and ice-sheets
on the one hand and volcanoes and lava
flows on the other. The vast region
just mentioned, embracing Idaho,
Oregon, Washington, California, Brit
ish Columbia and Alaska, was at one
time overfiowed by oceans of lava, and
afterward covered with great fresh
water lakes and huge ice-sheets and
glaciers.
The traveller encounters the first
sign of one of these phenomena, before
mentioned, on the Oregon Short Line
Railroad, between the boundaries of
Wyoming and Idaho. Here he will
meet the extreme border of what is
known as the Great Lava Flow of the
Northwest; body of lava comprised
of many different consecutive layers,
sheets and flows, that with little inter-
ruptiOn cover the greater part of
WASHINGTON. Idaho and Oregon for
over two hundred thousand square
miles, and are from three hundred to
three thousand feet thick. Over this
area, greater in extent than France,
there are few volcanic cones or era
ters to which these flows may owe their
origin. What few isolated crater
mountains there are, like Mt. Hood
and Mt. Tacoma, are restricted to the
Pacific Coast, and tho the fires in these
are not yet quite dead, we can in no
wise attribute the vast areal flows to
such limited sources. 1t seems more
probable that the earth opened its
mouth IN multitude of assures, from
which the molten floods poured like an
ocean of fire in successive flows over
the country, than that these vast sheets
were emitted from a few isolated vol
canlc cones or craters. In few fa
vored spots one can still find evidences
of the clefts that may have supplied
the lava, but now filled with soIic
banks of basalt-a very hard, greenish
black rock. Near Pocatello, on tht
Oregon Short Line, granite mountains
come down to the border of the grea
desert; and in the narrow valleys be
tween these hills we find the natura
water-courses filed by long flows O
black basaltic rock, just as if the mol
ten flood had poured down the valley
and driven the rivers from their natur
al beds, and then CONCEALED there, lik
the dross poured from the slag-pot o
smelling furnace. In some cases tn
rivers have recovered their natura
beds by cutting through the lava, an
so, as we 60 along the valley by tn
side of the stream, we pass throug
walls of black molten rock rising il
terraces of columns one above the 9th
er, on either side of the railroad track
The surface of these flows resemble
the top of honeycomb, owing to th
rude symmetrical cracks outlining th
divisions between the columns of th
lava sheet, which resemble those of th
Giants Causeway or the Palisades 9
the Hudson. The cracks, as we'll a
the columns, were formed by the COO
ing and contraction of the lava i
much the same way that cracks al
formed in the muddy bed of a pom
that is drying up. They descend Writ
cally through the lava sheet, outlinin
and deepening the forms of the pillar
or columns. Often, between thes
sheets of lava, there can be found
little terrace formed of rough, spong
cindery lava. This no doubt WI
caused by the froth charged with stear
on the top of one lava sheet before Il
second was poured on.