Yet all this gravel has been
transported, and probably rounded, subsequently to the deposition
of the white beds, and long subsequently to the underlying beds
with the tertiary shells.
Everything in this southern continent has been effected on a grand
scale: the land, from the Rio Plata to Tierra del Fuego, a distance
of 1200 miles, has been raised in mass (and in Patagonia to a
height of between 300 and 400 feet), within the period of the now
existing sea-shells. The old and weathered shells left on the
surface of the upraised plain still partially retain their colours.
The uprising movement has been interrupted by at least eight long
periods of rest, during which the sea ate deeply back into the
land, forming at successive levels the long lines of cliffs or
escarpments, which separate the different plains as they rise like
steps one behind the other. The elevatory movement, and the
eating-back power of the sea during the periods of rest, have been
equable over long lines of coast; for I was astonished to find that
the step-like plains stand at nearly corresponding heights at far
distant points. The lowest plain is 90 feet high; and the highest,
which I ascended near the coast, is 950 feet; and of this only
relics are left in the form of flat gravel-capped hills.
Pages:
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356