The L'Anse sentinel. (L'Anse, L.S., Mich.) 18??-current, 1897-11-06
THE CONTINENTAL EDGE.
The Sea Level Not "a Surface OF Un'-
form Curvature.

| form Curvature.
We may apply what may seem On
special portions of the coasthne 10 tne
whole margin of sea and land-to the
continental edge itself. From TINS
noint of view we soon learn that what
we call the mean level is not sur
face of uniform curvature, or an emp
sold inclosing smooth and theoretical
earth, but is bent up or down, according
IN the nearness or remoteness OF the
continental mass, so that the sea lever Is
high against the land and low in the
| center of the oceans. Could we remove
! the attraction of the continental
masses, many oceanic islands would
thus disappear beneath the waves.
Ice masses have naturally been IN
voked to account for some of the raised
beaches. An unusual accumulation OF
polar ice would draw the oceanic wa
! tiers northward and would raise the sea
level along our shores; but Lord Kelvin
has shown that the enormous thickness
| of the ice at one time demanded is n
physical impossibility in an uninclosed
basin, owing to the outward viscous
| HOW OF the W nv u NAN'' N'Ni'
! at polar temperatures, 10 thin and nat
| ten the whole mass. Nor would all
! the ice postulatcd by the EXTREMIST
! g'aciaist account for the uniting or
! local curvature of the she'll beds or ter
races that are left behind. The Chalk
hills of Alaska, TO quote one fine exam
pie, are composed of strata containing
shells still living in the adjacent ocean
Yet these beds, 1000 to 5000 feet in
thickness. are bent up so as to dipnorth-
ward at an angle of 10 to - degrees over
distance ofabout nine miles We have
here along the coast line of the Pacific
a range of hills 5000 feet in height-we
should call the mountains in our
own country-produccd by compara-
lively modern uplift along the con-
tinental edge.
Whether we study the American sea-
board down the volcanic hills of Chill
and Peru, or the coral coast of the In
dies and Australia, or our own storm
swept western promontories, we find
the same series of phenomena, the same
problem to be solved. 1t seems gem
orally agreed by this time that CONT
I
mental margins are unstable and that
they mark lines of movement in the
crust or skin Of the earth. The North
American continent is actually fanked
by mountain chains formed of in
tensely crumbled strata. and South
America presents toward the Pacific
its magnificent back bone of the Andes
The Pacific as whole is ringed about
with earth folds, the details of which
indicate spreading Of the continents
at the expense of the ocean basin; and
the progress of movement along these
lines of weakness is marked by violent
volcanic action.
Along the Pacific work is evidently
being done, and the deep oceanic de-
pressions bordering the continental
edges are the submerged limbs OF the
folds that form these lodges. The late
Prof. J. ID. Dana long ago pointed
out how the earth ridges and the long
oceanic grooves were related to one au-
other, the greater mountain chain hav-
ing the deeper depression along its
flank. In a word. as he urged, the
highest mountains faced the deepest
portions of the ocean, and their steep
err TANKS descend toward the OCEAN
London knowledge,