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Letter 3001A

Lyell, Charles to Darwin, C. R.

30 Nov 1860

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    Satisfied that CD finds his conjectured rate of elevation and long periods of stasis reasonable, even if these periods cannot be estimated. Explaining upheaval by subterranean lava flow makes these pauses plausible. Suspects that mountainous areas move more than lowland and coastal areas. General upheavals or subsidence in Europe in glacial period are unlikely. Believes with Jamieson that there was glacial action in Scotland before its submergence and that it was equally mountainous then. Subterranean upheaval visits different countries by turn. Horizontal Silurian strata must have been submerged and upheaved. Rest has always been the general surface character. Believes, however, that the quantity of late Tertiary movement is against CD's belief in the constancy of continents and oceans: perhaps since the Miocene period, but not since the Cretaceous.

Transcription

30. Nov. 1860

You must have thought so much, when on your coral-reef-areas, of subsidence & volcanic areas of elevation, that I think you high authority in speculations of that kind & if you think 212 feet per century a good allowance (as I believe it to be & above an average) & if you agree with me that between two great movements in an opposite direction there would generally be a long pause, I am satisfied; even if we have no means even of guessing at the probable duration of such pauses. Suppose the passage of a great subterranean lake of liquid lava into a crystalline rock to be the cause of secular upheaval—the heat gradually diminishing & the rock e.g. granite, expanding, it is likely that the rate of upheaval tho` it may be equable & persistent for tens of thousands of years, like the heat of thermal springs, will when on the decline, decrease very gradually & one cannot expect the reheating of the same mass or of one in the same part of the earth's crust & the melting thereof to take place just when the cooling had ceased.

The chances are that before the reversal of the movement there would be a very long interval. But you speak of astronomical causes. Did you ever read of any as yet suggested, which seemed in the least degree feasible, & one cannot doubt the connection in S. America of volcanicity & movements of upheaval & depression?

I understood, however, the force of your objection to my reasoning as to movements from space to time    If I were to judge by sea-coast evidence alone I should think a tenth rather than a fifth was all that is in motion. But I cannot help suspecting that the Alps & other mountain chains move more than lower countries. The Alps seem so often to have risen & sunk considerably. This perhaps strengthens your objection as showing that you cannot apply the rule of one area to another as certain spaces are repeatedly moved while others may continue at rest for one geological period after another. Spratt's proof of Candia or Crete nearly 100 miles long having gone down at one end— Greek cities being submerged & up at the other the old docks being upraised high & dry & in the intermediate space no movement, agrees with many facts to indicate that the Mediterranean is one of the areas of unequal movements in the last 2000 years. Smith of Jordanhill shows great oscillation of rock of Gibraltar since existing Mediterranean shells

On the other hand there are parts of Norway stationary where beaches with recent shells have been upheaved 700 feet. I doubt there having been periods of general-upward or general-downward movement in Europe in Glacial Period.

As to Scotland having been as high above the sea as now before the great submergence, all that I know of the Grampians, which are covered by unstratified till & old moraines, under these more modern gravels which Jamieson has correctly described at all heights lead me to the belief that Jamieson is right, p.p. 368--369, in believing that glaciers or land-ice in Scotland & Ireland acted powerfully before the land sank. You may say, however, that the land need not have been as high as now, but I think it more likely that it was, as the Scotch mountains are not high enough to have had glaciers on them, unless there was a great volume of land & that would almost imply height.

I shall take your hint & be satisfied in claiming, as a minimum, 100,000 years for the downward, & as much for the upward, movement, & then give as my reason for inferring a very long stationary intervening period, that so much of Europe, even where there has been pleistocene & post-pliocene upheaval & depression, as e.g. Scotland, part of Norway & parts of Sicily, have been at rest for last 2000 years.

You will have no objection I presume to my going so far without pretending to define by centuries the length of said interval.

My idea is that subterranean upheaval, like volcanos, shifts it's theatre of action & by degrees visits every country, & if there are Silurian regions of horizontal strata, they too can be proved to have been submerged & denuded, depressed & upheaved. As active volcanos occupy a small area so did extinct ones & so do deep-seated volcanic agencies or those causing upward & downward movements. Rest, therefore, always has been as it is now, the character of the surface generally, & change of level exceptional & inland sea-cliffs, like those of Greece or the Morea, show very long pauses. The quantity of pleistocene & post-pliocene movement makes me rather doubt the continents & oceanic basins remaining as constant as you suppose through several successive geological periods— From the Miocene to our era I can imagine it    But not from the Cretaceous to our times.

    Footnotes Add

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    f1 3001a.f1
    CD's Coral reefs was published in 1842. For his discussion with Lyell of the growth of coral islands, see Correspondence vol. 2.
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    f2 3001a.f2
    CD expressed his approval of Lyell's estimate of an elevation in the land of 212 feet per century in his letter to Charles Lyell, 25 November [1860]. Lyell cited CD on this point in C. Lyell 1863, p. 286.
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    f3 3001a.f3
    Spratt 1854. Lyell discussed Thomas Abel Brimage Spratt's observations on the geology of Crete in C. Lyell 1863, p. 178. Crete was formerly known as the island of Candia.
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    f4 3001a.f4
    J. Smith 1844.
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    f5 3001a.f5
    Jamieson 1860.
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