Part 1

TRANSCRIBER’S NOTE

Italic text is denoted by _underscores_.

Bold text is denoted by =equal signs=.

Small caps is converted to all caps.

Errata have been applied to the etext.

Footnotes have been relocated to the end of the etext.

Some minor changes to the text are noted at the end of the book.

Geological and Solar Climates

Their Causes and Variations.

A THESIS.

BY

MARSDEN MANSON, C. E.

_Geology and Physics_: UNIVERSITY OF CALIFORNIA, May, 1893.

Entered according to Act of Congress in the year 1893, By MARSDEN MANSON, In the office of the Librarian of Congress, at Washington, D. C.

SAN FRANCISCO: George Spaulding & Co., Printers. 414 Clay Street.

ERRATA.

Preface, next line to last, for _waiver_ read _waver_.

Page 5, foot-note, 7th line from bottom, for _Hetvetic_ read _Helvetic_.

Page 14, in foot-note, 6th line from top, for _Zenographic_ read _Zenographical_.

Page 17, last line, for _area_ read _era_.

Page 20, 14th line from top, for _wherever_ read _whenever_.

Page 23, 3d line from bottom, for _area_ read _era_.

Page 23, 4th line from bottom, for _merging_ read _emerging_.

Page 41, 15th line from top, after _necessary for the_, insert, _removal of glacial conditions, and for the_

Page 44, the second paragraph should read: The trapping process not being a function of the orbital distance, nor of the actual amount of heat received, but of the composition of the atmosphere, this rise, etc.

Page 47th, 6th line from top, insert ” at end of paragraph, after out.

_Ib_, 6th line from bottom, for * substitute †.

PREFACE.

The worshipers of truth are delving in every hamlet--many have before them the daily burdens of life, from which they can snatch but a few hours each day to give to their chosen faith.

Every now and then one comes forward with some skillfully carved jewel which he has wrought into shape to deck his shrine. Sometimes it is only a little piece merely good for inlaying the walls, yet it fits well in its place and strengthens the faith of other workers. Again it is the great keystone for some massive arch whose other stones were laid in bygone times. Yet again it is a mighty truth that will not fit in the great building at all until the wrong work be torn down, and then it forms the base for one of the steadfast and everlasting towers. So pure must be the faith of those who bow at the hallowed shrines of truth that they would tear down these shrines rather than let them stand upon, or even harbor error.

The writer gives in this little book a keystone which he knows will not fit in the present building unless some errors be torn out. Those whose faith is true will not waver nor come grudgingly to the work of rebuilding.

GEOLOGICAL AND SOLAR CLIMATES,

THEIR CAUSES AND VARIATIONS.

THE CAUSE OF THE ICE AGE.

“_The most important problem in terrestrial physics_ * * _and the one which will ultimately prove the most far reaching in its consequences, is: What are the physical causes which led to the Glacial Epoch and to all those great secular changes of climate which are known to have taken place during Geological Ages?_” (_Dr. Croll_, _Climate and Cosmology_.)

“_An attentive study of the physical Geography of the earth and its influences on Climate, together with a judicious application of the simplest physical theories, will enable us to gain by and by a better knowledge of Geological climates._” (_Prof. A. Woeikof_, _Nature_, _March 2, 1882, p. 426_.)

Since Agassiz announced[1] the past existence of an age during which ice covered temperate and tropical land areas, _the cause_ of this wonderful phenomenon has been a problem of profound interest. Upon the correct solution of it hinges also the cause of Geological climates.

So great has been the interest attaching to this subject, that more study has been devoted to it during the past fifty years than perhaps to any other in Geology; hardly a leading scientific magazine runs through a year’s numbers without one or more articles upon it; and no Geological Society is without zealous students of glacial phenomena. Some have become so absorbed in the subject that, led by the recurrence of certain slight astronomical influences, they recognize a glacial period for slight and widely scattered evidences of possible early local glaciation, forgetful of the fact that an era of frigid climate could not intervene between two eras of tropical climates without the intervention of eras of temperate climates.

The evidences establishing the reality of the Ice Age[2] during the Quaternary period are now beyond dispute. It is difficult, however, to establish by geological evidence the synchronal glaciation of all the continental areas known to have been heavily glaciated. This difficulty arises from the fact that the identity of various strata has to be established by fossils of varying conditions and characters; it is also rare that the same geologist has visited and compared the evidence upon more than two continents, thus eliminating probable errors from unequal sub-aerial denudation and exposure in the different zones of present climates and upon different continents. Again, the proof of the contemporaneous existence of corresponding strata upon different continents in the same latitude is sometimes attempted by a comparison of land fauna and flora, with marine fauna and flora, or even by more complex comparisons. Fossil plant life is by far more reliable than animal life for comparative purposes.

Another misleading factor is found in the interpretation of the great trans-continental lines of terminal moraines into the absolute limits of glaciation. Considering the great lapse of time since the removal of glacial conditions in temperate and tropical latitudes, it is more than probable that the existing unobliterated evidences by no means mark the extreme limits of a lighter and more extended glaciation whose traces have been destroyed, but which can justly be interpolated between the existing very marked traces of enormous glacial extension during Quaternary times. It is not impossible, nor entirely improbable, that early local glaciation did not occur during the early part of the Cenozoic Era, or even earlier, but the data upon which to establish the occurrence of such early local glaciation are both meagre and obscure. Should the evidences of such early local glaciation be developed beyond dispute, they will in no way interfere with the interpretation to be given, but they will strongly corroborate certain portions of this interpretation. So far as the author has been able to examine such evidence, it has been found to be between strata containing fossil life of a torrid character, with no evidences of a gradual merging into a temperate climate above and below it, as in Quaternary glaciation.[3]

Before entering further into this discussion, it may not be out of place to briefly review the principal theories advanced to account for the Ice Age. It will be seen that physicists and astronomers have vied with geologists in the diligence of the search for the cause of this age, and their minds have been as fertile in the number of causes assigned as the true one. Not one of all the causes suggested has been sustained by argument without a flaw in the reasoning, and no demonstration has been made which has carried conviction to the scientific world.

It would not be instructive to attempt to review all of the theories which have been urged. The tendency to ascribe remote inadequate or obscure causes, rather than to interpret facts and phenomena in accordance with known laws, is apparent in many. Some writers have ascribed causes resting only upon hypotheses beyond the range of either analysis or investigation; such hypotheses can only stand in the absence or failure of all other assignable causes. Therefore the leading causes only will be briefly mentioned.

In a recent monograph on the subject, the following are given:[4]

1. A decrease in the original heat of the globe.

2. Changes in the elevation of land, and consequent variations in the distribution of land and water.

3. Changes in the obliquity of the axis of the earth.

4. A period of greater moisture in the atmosphere.

5. Variations in the amount of heat radiated by the sun.

6. A variation in the heat absorbing power of the sun’s atmosphere.

7. Variations in the temperature of space.

8. A coincidence of an Aphelion winter with a period of maximum eccentricity of the earth’s orbit.

9. A combination of 8 and 2.

10. The views of Sir Robert Ball, LL. D., etc., as expressed in his recent work, _The Cause of an Ice Age_.[5]

The first of these theories is universally admitted, and taught in even elementary works on Physical Geography, but it fails to account for all the phenomena accompanying the Ice Age, or to account for the disappearance of that age, and, so far as the author is aware, has not been presented in such form as to satisfactorily account for geological and present climates in rigid conformity with the facts and known laws. Nor has it been presented in such form as to account for that era of geological climates known as the Ice Age; moreover, it fails to account for the disappearance of that Age.

The second has been proved to be a local and correlated phenomenon, but cannot be accepted as a _cause_, since glaciation did not solely depend in the same latitudes upon elevation above sea level.

As to the third, whilst slight changes in obliquity have occurred, and must continue to occur, the results are too slight and the distribution of glacial phenomena is too general to warrant the acceptance of such change as a prime cause.

The fourth is a necessary consequence of the first, but, like the first, fails when the crucial test of accounting for the disappearance of the continental Ice Sheets is applied.

The fifth, sixth and seventh theories are mere hypotheses, unsupported by either demonstration or observed facts.

The eighth has been presented to the scientific world through the labors and researches of that eminent geologist and physicist, Dr. James Croll, in his various articles in leading scientific magazines, and lastly, in his grand contributions to the subject under discussion, “Climate and Time” and “Climate and Cosmology.”

The ninth has been maintained by one of the greatest English naturalists, Mr. Alfred Russell Wallace. He combines the theory of Dr. Croll with that of Sir Charles Lyell, and very ably presents his views in “Island Life.”

The tenth is a presentation by Dr. Ball, F. R. S., etc., of an interesting demonstration, to the effect that 63 per cent. of solar heat reaches either hemisphere during its summer exposure, and the remaining 37 per cent. during winter exposure. Nothing is added to the Physical Theory of Dr. Croll, nor does the demonstration in any way remove the serious objections which have been urged against Dr. Croll’s views.

The strongest support that has been given to any of the above theories is made by the arguments and deductions of Dr. Croll and Mr. Wallace; yet they have failed to produce conviction, for, in a recent work on Geology, the author, after reviewing the various theories as to the cause of the Glacial Period, uses this expression: “This seems to be by far the most probable yet presented.”[6]

This opinion is directly given upon only one--the ninth; but its terms are such that it embraces all. If the ninth is “by far the most probable,” it would be difficult to fix the degree of probability or improbability of the others.

The only explanation which can be accepted is one which will admit of definite proof, and will satisfy all the conditions, and not require the distortion of known facts, by forcibly fitting them into arbitrary molds. It must start from universally admitted premises, and in rigid consonance with known laws, correctly interpret the grand eras of climate which have marked the geological history of our globe, and further, it must point out and fully elucidate wherein and why the present climates of our globe differ so radically from those vast secular variations recorded by fossil life--aye, more, it must be so general as to be of universal force and applicable to other members of the solar system constituted as our globe.

In the brief review just made of the principal theories urged by various scientists as causes producing the Ice Age, it was remarked of the first that it was universally admitted as true, and even taught in elementary works on Physical Geography, but that it failed to account for all the facts developed by the Ice Age. This first theory was a decrease in the original heat of the globe, the truth of which is established by a mass of indisputable geological evidence.

The present conditions are so radically different from any of the eras of climate known to have existed, that the explanation of this range of secular changes becomes the grandest problem in terrestrial physics, and has an important bearing in the solution of existing conditions upon the other planets.

It is universally admitted that this original heat has been so lost that it is no longer a factor in the surface temperature of the earth, and that solar energy is now the controlling source of heat.

There can then be no mistaking the first nor the present condition of the earth as regards its exposure to the only two sources of heat--(1) solar and stellar[7] heat, and (2) resident, internal, or earth heat. There can therefore be no error as to the main features of the problem.

There must have been two marked eras of climatic control--(A) a past era, during which both sources were active; (B) and the present era, in which the greater exterior source only remains, the local and lesser source having been practically exhausted.

Or, in other words, we have, _first_, a heated globe having resident in its mass a finite quantity of heat, undergoing loss and exposed to an exterior source of heat and light, which source may be either constant or decreasing in its energy, but so slowly that it may be considered sensibly constant during the eras under consideration; _second_, the same globe deprived of its heat to such an extent that a crust of non-conducting material has formed, the outer surface of which is exposed only to solar heat, and whose climates are entirely controlled thereby. The objects in view being to explain (1) the peculiar uniformity of climates prior to the exhaustion of the first source, and (2) the occurrence of an age of general glaciation in all latitudes prior to the establishment of the sole control of the exterior source; (3) the reasons of the differences between heat distribution during geological and present climates. Such explanations to be in strict conformity with admitted facts and known laws, and without omitting the one nor distorting the other.

To be explicit we will state that the prime objects are to demonstrate--

1. That in the passage of the earth from an era during which its climates have been controlled by internal heat into an era during which its climates are controlled by solar heat, eras of uniform climates must have been passed through during which isotherms were independent of latitude.

2. That before climates could have passed under solar control that an age must occur during which continental areas must be glaciated; and that this stupendous phenomenon, occurring before solar climatic control, was also independent of latitude.

3. That the direct _cause_ of the Ice Age was a combination of the remarkable properties, in relation to heat and cold, possessed by the various forms of water. As _vapor_, in the form of fogs and clouds it prevented the loss or receipt of heat by radiation; as _water_, by reason of its high specific heat, it retained to the last moment the effective remnant of earth heat; as _ice_, it assumed a solid form, storing the maximum amount of cold.

4. To point out in a general way the fallacies of previous attempts to explain geological and present climates.

The problem will be given in a general proposition, which is capable of demonstration in perfect accord with known laws.

[This demonstration was first given by the Author in September, 1891, and is reproduced here slightly modified and extended from Vol. VIII of the Transactions of the _Technical Society of the Pacific Coast_.]

THE GENERAL PROPOSITION.[8]

_GIVEN.--A heated globe, constituted and circumstanced as the earth, and whose surface temperatures, by reason of internal heat, are above the boiling point of water, to prove that before its surface temperatures can pass under the control of the solar heat_ (1) _that climatic changes must be independent of latitude, and_ (2) _that the continental areas_[9] _must be glaciated._

It will be observed that the surface temperatures of a globe thus situated are entirely controlled by its own internal or earth heat; for between such surface and any external source, a dense cloud of vapor must exist. The fact that direct or radiant heat rays cannot pass through dense fogs and clouds is well known;[10] therefore, a globe thus situated can neither give off, nor receive radiant heat. The peculiar function of solar heat during the existence of appreciable quantities of earth heat was to warm the upper regions of the atmosphere and the outer surface of the clouds exposed to its power, thus partly replacing the heat lost by radiation into space, and causing the store of earth heat to last longer.

By the conditions of the problem presented, we thus have a globe having resident in its mass a finite quantity of heat exposed to loss only by means of the gradual expansion of water into vapor, and the exposure of this vapor to loss of heat by radiation from its upper surface into space. This vapor would then condense, and as rain, snow or hail, descend all, or part of the way to the earth, receive another increment of heat, and ascend as before. A slow process, but exhaustive in time.

Thus the property of water to assume three forms, each of which possesses remarkable qualities with regard to heat and cold, afforded the only means for exhausting the earth heat. As vapor, it possesses the property of storing more heat than any other known substance;[11] as snow or ice it possesses the property of storing more cold than any other known substance. The function of solar heat, until the exhaustion of earth heat by this process, was simply conservative; it merely warmed the upper layers of the atmosphere, through whose dense vapor its heat rays could not pass. Clouds being more translucent than transcalent, light rays reached the planetary surface prior to heat rays.

The earth may thus be regarded as having been surrounded by a series of spheroidal isothermal shells of mean temperatures. The one next the surface represented a mean temperature of 212° + t° Far.; t being positive, and proportioned to the greater pressure of the heavier atmosphere existing. Above this isothermal shell were others representing mean temperatures of 90°, 60°, 32°, Zero, etc., to -x° Far., the extreme cold of interplanetary space. Between the two spheroidal isotherms of 32° and -x° Far., was one which had a mean temperature of 32° - y°, and equally exposed to both sources of heat.

That the spheroidal isotherm of 32° Far. was within the sphere of influence of earth heat, is proven by the formation of snow or ice at that temperature, both being the resultant of vapor expanded and raised by earth heat to that height as a minimum. Moreover, vapor would have reached that height as a minimum were solar and stellar heat suspended for a definite period, and the earth absolutely exposed to loss by radiation with no partial return of heat, from exterior sources.

It therefore follows that the isotherm equally heated by both exterior and interior sources was colder than 32° Far. or below that temperature at which snow and ice form. (It is well known that solar energy cannot maintain a temperature as high as 32° Far. except in the lower regions of the atmosphere.)

The isothermal shells nearest the earth were spheroidal in shape, and by reason of the conditions their surfaces were practically parallel with that of the earth; those most remote from the earth, by reason of solar influences, protruded at the equator and flattened at the poles, so as to be slightly more oblate than the earth; they were sensibly parallel with the spheroidal isotherm now marked by the “snow line.” Hence at the equator the direct action of the sun was first felt and established.

As the earth heat was a finite quantity exposed to loss, it was in time exhausted. As this loss proceeded, these spheroidal isothermal shells of mean temperatures shrunk in upon the earth, and their contact with its surface marked the zones of corresponding climates prevailing during the dual source of heat. Since these isotherms were independent of equatorial or polar exposure to solar energy their contacts with the planetary surface established climates independent of equatorial or polar position, or in other words of latitude; and not until those, whose distance from the surface mainly depended upon solar energy, shrunk to the surface could climates ranged in latitudinal zones be established. As the climates established by the contact of the isotherms inside of 32° - y° Far. were independent of direct solar heat, they varied from the climates established by solar heat alone; hence the marked difference between climates antedating and succeeding the Ice Age. The isotherms preceding this age were dependent almost entirely upon elevation above sea level, fractures and conductivity of the earth’s crust; those succeeding it are dependent upon proximity to the equator, elevation above sea level, and the distribution of heat by ocean currents.

At the expiration of a period of time T., the earth lost sufficient heat to cause the isothermal shell of 90° Far. to shrink to the surface except at fractures, and a particularly uniform, moist, and highly torrid climate was established, and types of life developed, culminating in the Carboniferous Age.

The crust cooled sufficiently to permit the demarkation of the continental areas, but the cooling did not proceed to that point which upheaved the massive mountain ranges, nor greatly depressed the ocean areas. Therefore, an era of low, flat continents, and shallow hot seas followed. The life of that period abundantly shows this condition from one pole to the other, and the prevailing temperature is distinctly recorded in the fossil life of the Palæozoic and Mesozoic Eras.

Light rays reached the surface prior to this time, as evidenced by the development of visual organs in animal life.

The greater part of the vapors and gases existing previously in the atmosphere were condensed, and existed upon the surface; the vapors as highly heated oceans, and the gases in various combinations of the mineral and life kingdoms. Now, in the oceans thus formed and further enlarged, there was stored up a vast quantity of the original earth heat, by reason of the _high specific heat of water_, from which it was not exhausted until the last moment; and in this process of exhaustion, it must have maintained the cloud shield, shutting out solar heat until this the last remnant of effective earth heat was exhausted. Not only this, the oceans thus formed had a mean temperature of 90° + z° Far., z being a positive increment due to the heat received from the bottoms and sides of the ocean. Not until the bottoms of the oceans were subjected to a degree of cold approximating that to which the continental areas were exposed could the crust be cooled uniformly and reach that degree of uniform thickness and stability suitable to the safety and comfort of the human race.[12]