TRANSCRIBER’S NOTE
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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]
At the expiration of the period of time, T′, the spheroidal isothermal
shell having a mean temperature of 60° Far., similarly shrunk to the
surface of the earth, and a corresponding uniformly temperate climate
was established.
The further cooling of the crust caused its shrinkage, and a consequent
greater upheaval of those areas most exposed to loss of heat, the
continents. This further shrinkage caused the strata formed during
the previous eras to be upheaved and fractured, and the lines of
demarkation between oceans and continents were thus more strongly
accentuated.
The life developed in the interim evidences an approach to that of the
present temperate zones, and its wide distribution demonstrates the
complete control of the climates of the globe by internal heat. The
isothermal lines were entirely at variance with those established by
solar heat, therefore the functions of solar heat remained conservative
of those operating on the surface during this period also.
The extreme and uniform distribution of fur or hair-covered animals and
of the deciduous and coniferous trees of the Cenozoic era mark further
the control of a source of heat more uniformly distributed than solar
heat could possibly be. For reasons previously given, this isotherm
also reached continental areas earlier than ocean areas. When the mean
temperature of the land was 60° the tepid oceans must have had a mean
temperature of 60° + y° Far., y, like z, being positive, and due to
increments of earth heat received from the bottom.
At the expiration of this period T′, or at some time, T′ ± a, the
isothermal shell of 32° Far. shrunk so as to reach the more elevated
portions of the continental areas, and thus established a snow line
independent of the influences now establishing and maintaining such
snow line. The resulting glaciation was controlled by the same general
laws that now exist, only the distribution of heat being independent
of latitude, and mainly dependent upon altitude above sea level,
glaciation of present tropical and temperate latitudes was as certain
to occur as in polar regions. The moment a snowflake reached the
earth which the waning earth heat was unable to melt, the Ice Age was
inaugurated; and the conditions were such as to favor its extension
until the exhaustion of the store of heat beneath the oceans and
resident in them, by reason of the high specific heat of water. It will
be noted here that whenever, in obedience to the expansive force of
this waning earth heat, a particle of water was vaporized and made the
last round of its circulation, it returned to the earth in that form
which stored the maximum degree of cold, or, in other words, in that
form which required the maximum amount of solar heat to change.
From the moment that snow began to accumulate, every remaining vestige
of earth heat was available for producing those conditions favorable
to glaciation, namely, warm seas, dense fogs and cold continental
areas; and every unit of solar energy reaching the upper regions
of the atmosphere was available for maintaining those favorable
conditions.[13] Glaciation under these conditions would be cumulative
until the oceans, exhausted of their heat and lessened in area, were
no longer able to supply the moisture necessary to completely shroud
the earth from direct solar heat.
At the expiration of the time T″, the isothermal shell, having a mean
temperature of 32° Far., shrunk in upon the globe, and the oceans
were exhausted of their store of heat and their bottoms brought in
contact with water having a mean temperature of 31° Far., a temperature
approximating that of the ocean depths at present, and of ice in masses.
The isothermal shell 32° Far. was a spheroid circumscribing the earth.
In shrinking to the earth its intersections with the surface were
controlled by the elevation of the surface above sea level, and by the
local escape of earth heat; elevated equatorial or temperate areas were
therefore as much exposed to glaciation as polar lands. (For maximum
depth of glaciation see page 32.) By reason of the high specific
heat of water, this isotherm also reached continental areas prior to
reaching ocean areas.
The crust beneath the ocean, having been protected from loss of heat
by the superincumbent water, shrunk to its final shape subsequent
to that portion forming continental areas. The ocean bottoms in
thus shrinking approximately to their present shape must have been
fractured, as continental areas had previously been. In this way very
considerable increments of earth heat were set free after glaciation
had commenced. This process, which is entirely in consonance with known
laws, would result in increasing the depth of glaciation, or even in
re-establishing it after partial recedence.
There would also result a complicated series of crust movements as
the continents were relieved of pressure by the melting of the ice
caps, and the ocean bottoms subjected to increased pressure by the
restoration of water to the oceans.[14]
Thus the same forces which, even before the eras we have been
considering, must have built up upon the surface of the globe
mineral forms of surpassing beauty, only to be destroyed and ground
down to give place to vegetable and animal forms of wonderful
development--these same forces were called upon to well nigh obliterate
every living individual of both kingdoms. The efficiency of their work
is attested in every zone of life from the equator to the poles.
The exhaustion of the residuum of earth heat in the oceans and beneath
them could only have been accomplished by the same means as before,
and this exhaustion resulted in the preservation of those conditions
most favorable to glaciation. When by the chilling of the oceans to
about 31° Far. and by the glaciation of continental areas, the air was
cleared of obscuring clouds and fogs, the wonderfully uniform series of
climates was at an end.
With the dominion of solar heat there dawned upon our planet an era
of climatic zones whose lines sensibly follow parallels of latitude;
then also began seasons of spring, summer, autumn and winter, with the
varying changes of the earth’s annual round.
The climatic changes during the control of earth heat, and within the
range of geological research extended over eras:
1. An era of torrid heat.
2. An era of tropical heat.
3. An era of temperate heat.
4. An era of glacial cold.
Each merged gradually into the others, but each recorded its period of
existence in unmistakable terms, all shrouded from the direct action
of solar heat, and all evidencing by the life produced, the stifling,
smothered character of the climate.
That solar heat was shut out from the surface of the earth during
the Ice Age is geologically recorded in the glaciation of the North
Temperate Zone over continental areas, where solar energy has removed
glacial cold and established in its stead a mean annual temperature
of 40° Far., and in the torrid zone it has removed glacial cold and
established a mean annual temperature of 76° Far., where snow never
falls.
Consequently, in a heated globe, constituted and circumstanced as the
earth, exposed to two sources of heat, internal heat and solar heat,
before its climates or surface temperature can pass under the control
of solar heat climatic changes must be independent of latitude and the
continental areas must be glaciated.
A GENERAL COMPARISON OF THE DEMONSTRATION WITH THE FACTS OF GEOLOGY.
The dawn of the Archæan Era found the earth a heated globe emerging
from an unrecorded and unfathomable era of greater heat. The
crystalline character of the earliest rocks demonstrates the high
temperature which prevailed upon the surface at that time. Such
being the temperature of the surface, it is beyond question that the
existence of uncombined water upon it was an impossibility, and as
vapor it could only shroud the earth in dense clouds. The earth heat
was as effectually shut _in_ from loss by radiation as was solar heat
shut _out_ from reaching the surface.
As this finite amount of earth heat could only escape by doing _work_
in the expanding of water to vapor, vast eras of time must elapse
before the work done could exhaust the available heat. The process
of exhaustion was further retarded by two causes: 1st, the heating
of the outer layers of the atmosphere by solar heat; and 2d, the low
conductivity of the strata of the earth itself; consequently the
climates of the earth, until the final exhaustion of earth heat, being
controlled by a uniformly distributed supply, were of remarkable
uniformity. The denudations, faults and fractures of its crust set free
additional increments of heat but slowly, so that the torrid, tropical
and temperate eras were longer than the frigid era.
During the existence of sensible quantities of earth heat the oceans
must have been heated from the bottom, and cooled at the surface by
evaporation. The evaporation from the total ocean surface under such
conditions would give rise to much more extensive cloud formations than
at present. Indeed, the record of temperatures and character of life
are such as to warrant--nay, even force--the conclusion that the whole
earth was one vast hothouse, from which solar heat was shut out, and
throughout which a uniform temperature was prevalent from pole to pole.
Solar heat does not penetrate the thinnest cloud; even a fog through
which the form of the sun is distinctly visible shuts out nearly
all direct solar heat.[15] The failure in the past to recognize the
climatic influence which the factor earth heat was able to produce,
and the endeavor to ascribe to solar energy the climatic conditions
existing during the activity of earth heat, has caused all the mystery
and error of attempts to explain the climatic phenomena prior to and
during the Ice Age.
Once realize the peculiar influence and domination of earth heat, and
these mysteries and errors fade, and the whole system of pre-glacial
and glacial climates becomes simple.
The function of solar heat during the activity of earth heat could be
none other than conservative of the latter; such function it is now
performing for the great planets, Jupiter and Saturn, and probably
Uranus and Neptune, whose surfaces are shrouded from our view by
clouds.[16]
_Climatic Facts Established by Fossil Life._
It would be impossible, in the limits to which it is necessary to
restrict this paper, to review the vast array of facts which could be
brought forward to demonstrate the perfectly uniform, torrid character
of the climates of the globe during the Palæozoic Era.
From the 81st degree of north latitude through every range of present
climates to the confines of the south frigid zone, the life systems
attest the stifling hothouse character of the climate. The species of
plant life and animal life, whether of land or marine forms, varied
less from the torrid to the frigid zones than corresponding species
upon different continents in the same zone do now. Nowhere below the
Permian deposits can fossil life be recognized that does not belong to
an ultra-tropical type. Such uniformity of temperature is impossible
under solar control, and hence can only belong to a climate controlled
by earth heat.
In reviewing the temperatures recorded by the fossil life of the
Palæozoic Era, the fact becomes apparent that nowhere upon the surface
of the globe during that era were there any zones of temperature. The
whole surface was subjected to one universal torrid climate--the life
developed was uniform in its general character from the Arctic to the
Antarctic circle. Under no possible conditions could such uniformity of
climate have been established and controlled by solar heat alone. Hence
during this period earth heat was the controlling source.
This era merged gradually into the Mesozoic era of tropical heat,
during which the forms of life developed into higher types, and their
range of distribution demonstrates the still perfect uniformity
of climate. One peculiar and significant fact is recognizable in
comparing the land forms with the marine forms of life. The former
developed types more suitable to tropical climates, while the latter
held more tenaciously to the torrid types, thus proving the more rapid
loss of heat by the continents.
The fossil life of the Cenozoic era corroborates to a remarkable degree
the still perfect uniformity of climate. Throughout Greenland, Iceland,
Lapland and Spitzbergen, as well as throughout present temperate and
tropical zones, a perfectly uniform and temperate climate existed. The
flora and fauna of the lower Mississippi valley flourished in those
localities in which, during the Palæozoic era, only gigantic _Ferns_,
_Lycopods_, _Calamites_ and corresponding plant and animal life could
be found, and where now only a stunted Arctic life can exist.
The palæontological evidence of the Mesozoic and Cenozoic eras is
equally convincing as to the perfectly uniform tropical climate of the
one and temperate and later frigid climates of the other.
During the latter part of the Tertiary and early Quaternary periods
identical types of life existed in all parts of Europe, Asia and
America and a uniformly temperate climate prevailed over the whole
northern hemisphere entirely at variance with the extreme range of
temperatures now embraced in that half of the globe.
The control of the waning earth heat was simply dying out, and had
reached that stage in which it was no longer able to maintain the high
temperatures of previous eras.[17]
The evidence that the high specific heat of water held the last
available remnant of earth heat, and thus perpetuated its control of
climates, is beyond dispute, as presented by the conditions culminating
in the Ice Age.
Whatever may be the doubts as to the actual date of the Ice Age,
there is no disputing the fact that the evidences establishing the
culmination of that Age are found _above_ or since the Tertiary, and
_below_ or before the Modern Era.
Between these two periods there is abundant evidence from every
climate, from every zone of present life, that the continents were
glaciated.
Europe and Asia, North and South America, Africa and Australia,[18] all
present glacial striæ, boulder deposits, and other marked evidences
of glaciation at the same period, just antedating the Modern Era, or
during the Quaternary period.
When we examine the evidence found in one of the present climatic
zones, this change of climate from an ultra-torrid successively to a
torrid, tropical, temperate, and, lastly frigid character, is not only
very marked, but is everywhere the same.
Upon the establishment of solar heat in the control of surface
temperatures, we find the isotherms entirely at variance with those
antedating the Ice Age. We find also strong corroboration in the lines
of retreat of the continental ice caps. These lines are sensibly
parallel with the isotherms established by solar heat, proving that
solar heat was the cause of the disappearance of glacial conditions.
These facts distinctly prove the totally different source and
distribution of heat before and since the Ice Age, and that upon the
inauguration of climates controlled by solar energy, an obliteration of
the conditions left upon the dying out of earth heat set in. Along that
zone most exposed to solar energy conditions and life corresponding to
the tropical conditions of Cenozoic times have been established; along
those zones moderately exposed to solar energy the newly established
conditions are analogous to the universally temperate climate of the
latter Tertiary and early Quaternary periods; whilst in those zones
least exposed to solar energy a removal of glacial conditions is yet in
progress.[19]
Wherever fossil life has been developed the order of climates, as thus
recorded has been: First, torrid; second, tropical; third, temperate;
fourth, frigid; and fifth, the life appropriate to the zone of solar
climate--irrespective of that existing previous to the Ice Age. The
same order is true for any portion of either temperate zone; under the
equator the order of climates has been the same, except a return to
tropical conditions and life.[20]
In the North frigid zone this same order of climates has been found,
except that there has been no change from the conditions left upon the
dying out of earth heat; in other words, solar energy has not removed
glacial cold in those regions least exposed to its action.
The removal of glacial conditions has been less in the Antarctic than
in the Arctic regions, partly from causes pointed out by Maury, and
more fully treated by Dr. Croll. This removal has also been subjected
to variations due to the mild astronomical influences ascribed by
Adhémar, Croll, Ball, Drayson and others, as sufficient to produce
glaciation.
These astronomical causes undoubtedly must have produced slight secular
variations in the relative exposures of the two hemispheres to solar
heat--but they have not been demonstrated to be of sufficient influence
to produce glaciation, and in no way could they sensibly affect
climates prior to the establishment of the control of solar heat. (See
page 41.)
The distribution of heat, prior to the Ice Age, as recorded by fossil
life, being entirely at variance with that now found, and being
entirely independent of proximity to, or distance from, the equator,
distinctly proves that climates were established and maintained
independently of solar heat, and hence belong to the only other source,
viz., earth heat.
It is also evident that under no possible conditions could solar energy
maintain a torrid, tropical, temperate and lastly glacial climate over
the whole range of the present zones of climates, and that this uniform
distribution of heat prior to and during the glaciation of the globe
was due to an evenly distributed supply from a constantly and uniformly
decreasing source.
Moreover, the wide distribution of glaciation over the present
temperate and torrid zones is a distinct proof of the exclusion of
solar heat from these regions during glaciation. Under no possible
circumstances could temperate North America, Europe and Asia and
tropical South America have been glaciated unless these regions were
shut out during glaciation from that solar energy, which when admitted
has removed glacial conditions.
Glacial dispersion followed one of two general laws: First, the great
centers or belts from which dispersion took place in apparent disregard
of the slope of the ground were areas most exposed to cyclonic activity
and resulting precipitation. Second, minor centers of dispersion (or
local glacial dispersion) were elevated lands, subjected to uniform
precipitation.[21]
Since glacial conditions in the northern hemisphere were removed from
southerly towards northerly latitudes, the gradients were increased
southerly and decreased northerly from lines of maximum glaciation.
Glacial transportation was likewise modified. The reverse of these
directions prevailed in the southern hemisphere.
Glaciated areas have been partly relieved of their loads of ice
at rates and times proportional to solar exposure, and upon lines
parallel with present mean annual isotherms. Wherever remnants of the
continental ice sheets of the Ice Age yet rest, this retreat is still
in progress from the same cause.
The ascription of great elevations above sea level during the Ice Age
is natural, and such apparent greater elevation is due to _two_ causes
during this period, whilst due to only _one_ cause during previous
eras. As the surface of the earth became subjected to a temperature
of 31° Far. under the oceans, and a corresponding temperature under
the continental ice caps, contraction and consequent elevation were
continued as before; and as snow was piled up upon the continents,
water was withdrawn from the oceans; for each million square miles of
continental ice cap three hundred feet thick a corresponding three
million square miles of ocean was lowered one hundred feet. The
continental ice caps already approximately known were too vast not to
have lowered the sea level to a marked degree.
The apparent general depression after the Ice Age is as natural. By the
melting of the greater portion of the ice caps, and the evaporation
of vast inland seas, the sea was approximately restored to the level
existing prior to the Ice Age, thus causing an apparent sinking of the
land.
The great difference between climatic conditions prior to and since
the Ice Age is very marked around inland seas and basins without
drainage. Lake Bonneville and Lake Lahontan, in the United States, and
the greater area once occupied by the Caspian and other seas, evidence
the superior dampness and rainfall antedating the Ice Age. During the
control of earth heat the oceans were heated to their bottoms, and
furnished moisture enough to keep these great depressions full of water
and to support a dense life upon now desert areas. The dry air of the
modern era has not only absorbed the water in these vast lakes, and
restored it to the oceans, but vaster areas have been converted into
deserts by the unequal distribution of heat and moisture under solar
control.
PALÆOZOIC GLACIATION.
“_Glacial Periods._”
It is probable and may be regarded as a fact that upon certain of the
oldest and highest mountains, glaciation was inaugurated during the
Palæozoic Era, to slowly disappear by the gradual setting free of earth
heat by vast fractures of the crust or to remain as local glaciation
until the Ice Age. Isolated glacial deposits of this nature which were
independent of solar exposure readily account for the early “Glacial
Periods,” which were evidently local phenomena antedating the Ice
Age. It is neither logical nor reasonable to interpret the finding
of evidences of early local glaciation into a Glacial Period, for
local glaciations are found now in the Alps and upon certain peaks of
the Sierra Nevada, and even in the torrid zone, but they by no means
establish the present existence of a Glacial Period.
Evidences of glaciations antedating the Ice Age are wholly of a
mechanical nature--namely, the transportation of boulders, striæ, etc.
No corroborative evidence of fossil life of Arctic habits has been
found. This is particularly the case of marine fauna and flora, which
may be held as the only indisputable evidence of an Ice Age.
Granting that the evidences found be sufficient to establish Palæozoic
glaciations, the absence of fossils of an Arctic type proves such
glaciations to have been local and possibly of short duration, for had
such glaciation been general and of long duration both plant and animal
life would have been modified into temperate and Arctic types, as
occurred later when general glaciation ensued.
It is apparent that the isotherm 32° Far. could have shrunk for a short
period to the tops of mountains and that glaciers could have formed
and coursed their way into a sub-tropical growth below; and that these
conditions would be removed by the setting free of earth heat with the
consequent rise in temperatures.
These changes followed too closely or were too limited in area to
permit the evolution of forms of continental life adapted to temperate
and Arctic conditions.
Palæozoic glaciations in no way conflict with the demonstration herein
given--they are really corroborative of the other facts advanced to
prove that prior to the Ice Age solar heat was shut out from the
surface. For the evidences of Palæozoic glaciation occur in temperate
and tropical latitudes adjacent to fossil life indicative of high
temperatures. Early glaciations were dependent only upon elevation, and
latitude did not influence their occurrence in any way whatever, and
whether in Norway or India these glacial conditions were coexistent
with tropical life at a lower elevation and equally independent of
latitude.