VIEW THE MOBILE VERSION of www.sustainablefarming.ca Informational Site Network Informational
Privacy

Most Viewed

Conclusion

Causes Of Mild Geological Climates

Hypotheses Of Climatic Change

Some Problems Of Glacial Periods

The Climate Of History

The Variability Of Climate

The Climatic Stress Of The Fourteenth Century

The Uniformity Of Climate

Glaciation According To The Solar-cyclonic Hypothesis[38]

The Solar Cyclonic Hypothesis



Least Viewed

Terrestrial Causes Of Climatic Changes

The Changing Composition Of Oceans And Atmosphere

The Sun's Journey Through Space

Post-glacial Crustal Movements And Climatic Changes

The Earth's Crust And The Sun

The Effect Of Other Bodies On The Sun

The Origin Of Loess

The Solar Cyclonic Hypothesis

Glaciation According To The Solar-cyclonic Hypothesis[38]

The Uniformity Of Climate






Some Problems Of Glacial Periods








Having outlined in general terms the coming of the ice sheets and their
disappearance, we are now ready to discuss certain problems of
compelling climatic interest. The discussion will be grouped under five
heads: (I) the localization of glaciation; (II) the sudden coming of
glaciation; (III) peculiar variations in the height of the snow line and
of glaciation; (IV) lakes and other evidences of humidity in unglaciated
regions during the glacial epochs; (V) glaciation at sea level and in
low latitudes in the Permian and Proterozoic eras. The discussion of
perhaps the most difficult of all climatic problems of glaciation, that
of the succession of cold glacial and mild inter-glacial epochs, has
been postponed to the next to the final chapter of this book. It cannot
be properly considered until we take up the history of solar
disturbances.

I. The first problem, the localization of the ice sheets, arises from
the fact that in both the Pleistocene and the Permian periods glaciation
was remarkably limited. In neither period were all parts of high
latitudes glaciated; yet in both cases glaciation occurred in large
regions in lower latitudes. Many explanations of this localization have
been offered, but most are entirely inadequate. Even hypotheses with
something of proven worth, such as those of variations in volcanic dust
and in atmospheric carbon dioxide, fail to account for localization. The
cyclonic form of the solar hypothesis, however, seems to afford a
satisfactory explanation.

The distribution of the ice in the last glacial period is well known,
and is shown in Fig. 6. Four-fifths of the ice-covered area, which was
eight million square miles, more or less, was near the borders of the
North Atlantic in eastern North America and northwestern Europe. The ice
spread out from two great centers in North America, the Labradorean east
of Hudson Bay, and the Keewatin west of the bay. There were also many
glaciers in the western mountains, especially in Canada, while
subordinate centers occurred in Newfoundland, the Adirondacks, and the
White Mountains. The main ice sheet at its maximum extension reached as
far south as latitude 39 deg. in Kansas and Kentucky, and 37 deg. in Illinois.
Huge boulders were transferred more than one thousand miles from their
source in Canada. The northward extension was somewhat less. Indeed, the
northern margin of the continent was apparently relatively little
glaciated and much of Alaska unglaciated. Why should northern Kentucky
be glaciated when northern Alaska was not?

In Europe the chief center from which the continental glacier moved was
the Scandinavian highlands. It pushed across the depression now occupied
by the Baltic to southern Russia and across the North Sea depression to
England and Belgium. The Alps formed a center of considerable
importance, and there were minor centers in Scotland, Ireland, the
Pyrenees, Apennines, Caucasus, and Urals. In Asia numerous ranges also
contained large glaciers, but practically all the glaciation was of the
alpine type and very little of the vast northern lowland was covered
with ice.

In the southern hemisphere glaciation at low latitudes was less striking
than in the northern hemisphere. Most of the increase in the areas of
ice was confined to mountains which today receive heavy precipitation
and still contain small glaciers. Indeed, except for relatively slight
glaciation in the Australian Alps and in Tasmania, most of the
Pleistocene glaciation in the southern hemisphere was merely an
extension of existing glaciers, such as those of south Chile, New
Zealand, and the Andes. Nevertheless, fairly extensive glaciation
existed much nearer the equator than is now the case.

In considering the localization of Pleistocene glaciation, three main
factors must be taken into account, namely, temperature, topography, and
precipitation. The absence of glaciation in large parts of the Arctic
regions of North America and of Asia makes it certain that low
temperature was not the controlling factor. Aside from Antarctica, the
coldest place in the world is northeastern Siberia. There for seven
months the average temperature is below 0 deg.C., while the mean for the
whole year is below -10 deg.C. If the temperature during a glacial period
averaged 6 deg.C. lower than now, as is commonly supposed, this part of
Siberia would have had a temperature below freezing for at least nine
months out of the twelve even if there were no snowfield to keep the
summers cold. Yet even under such conditions no glaciation occurred,
although in other places, such as parts of Canada and northwestern
Europe, intense glaciation occurred where the mean temperature is much
higher.

The topography of the lands apparently had much more influence upon the
localization of glaciation than did temperature. Its effect, however,
was always to cause glaciation exactly where it would be expected and
not in unexpected places as actually occurred. For example, in North
America the western side of the Canadian Rockies suffered intense
glaciation, for there precipitation was heavy because the westerly winds
from the Pacific are forced to give up their moisture as they rise. In
the same way the western side of the Sierra Nevadas was much more
heavily glaciated than the eastern side. In similar fashion the windward
slopes of the Alps, the Caucasus, the Himalayas, and many other mountain
ranges suffered extensive glaciation. Low temperature does not seem to
have been the cause of this glaciation, for in that case it is hard to
see why both sides of the various ranges did not show an equal
percentage of increase in the size of their icefields.

From what has been said as to temperature and topography, it is evident
that variations in precipitation have had much more to do with
glaciation than have variations in temperature. In the Arctic lowlands
and on the leeward side of mountains, the slight development of
glaciation appears to have been due to scarcity of precipitation. On the
windward side of mountains, on the other hand, a notable increase in
precipitation seems to have led to abundant glaciation. Such an increase
in precipitation must be dependent on increased evaporation and this
could arise either from relatively high temperature or strong winds.
Since the temperature in the glacial period was lower than now, we seem
forced to attribute the increased precipitation to a strengthening of
the winds. If the westerly winds from the Pacific should increase in
strength and waft more moisture to the western side of the Canadian
Rockies, or if similar winds increased the snowfall on the upper slopes
of the Alps or the Tian-Shan Mountains, the glaciers would extend lower
than now without any change in temperature.

Although the incompetence of low temperature to cause glaciation, and
the relative unimportance of the mountains in northeastern Canada and
northwestern Europe throw most glacial hypotheses out of court, they are
in harmony with the cyclonic hypothesis. The answer of that hypothesis
to the problem of the localization of ice sheets seems to be found in
certain maps of storminess and rainfall in relation to solar activity.
In Fig. 2 a marked belt of increased storminess at times of many
sunspots is seen in southern Canada. A comparison of this with a series
of maps given in Earth and Sun shows that the stormy belt tends to
migrate northward in harmony with an increase in the activity of the
sun's atmosphere. If the sun were sufficiently active the belt of
maximum storminess would apparently pass through the Keewatin and
Labradorean centers of glaciation instead of well to the south of them,
as at present. It would presumably cross another center in Greenland,
and then would traverse the fourth of the great centers of Pleistocene
glaciation in Scandinavia. It would not succeed in traversing northern
Asia, however, any more than it does now, because of the great
high-pressure area which develops there in winter. When the ice sheets
expanded from the main centers of glaciation, the belt of storms would
be pushed southward and outward. Thus it might give rise to minor
centers of glaciers such as the Patrician between Hudson Bay and Lake
Superior, or the centers in Ireland, Cornwall, Wales, and the northern
Ural Mountains. As the main ice sheets advanced, however, the minor
centers would be overridden and the entire mass of ice would be merged
into one vast expanse in the Atlantic portion of each of the two
continents.

In this connection it may be well to consider briefly the most recent
hypothesis as to the growth and hence the localization of glaciation. In
1911 and more fully in 1915, Hobbs,[46] advanced the anti-cyclonic
hypothesis of the origin of ice sheets. This hypothesis has the great
merit of focusing attention upon the fact that ice sheets are pronounced
anti-cyclonic regions of high pressure. This is proved by the strong
outblowing winds which prevail along their margins. Such winds must, of
course, be balanced by inward-moving winds at high levels. Abundant
observations prove that such is the case. For example, balloons sent up
by Barkow near the margin of the Antarctic ice sheet reveal the
occurrence of inblowing winds, although they rarely occur below a height
of 9000 meters. The abundant data gathered by Guervain on the coast of
Greenland indicate that outblowing winds prevail up to a height of about
4000 meters. At that height inblowing winds commence and increase in
frequency until at an altitude of over 5000 meters they become more
common than outblowing winds. It should be noted, however, that in both
Antarctica and Greenland, although the winds at an elevation of less
than a thousand meters generally blow outward, there are frequent and
decided departures from this rule, so that "variable winds" are quite
commonly mentioned in the reports of expeditions and balloon soundings.

The undoubted anti-cyclonic conditions which Hobbs thus calls to the
attention of scientists seem to him to necessitate a peculiar mechanism
in order to produce the snow which feeds the glaciers. He assumes that
the winds which blow toward the centers of the ice sheets at high levels
carry the necessary moisture by which the glaciers grow. When the air
descends in the centers of the highs, it is supposed to be chilled on
reaching the surface of the ice, and hence to give up its moisture in
the form of minute crystals. This conclusion is doubtful for several
reasons. In the first place, Hobbs does not seem to appreciate the
importance of the variable winds which he quotes Arctic and Antarctic
explorers as describing quite frequently on the edges of the ice sheets.
They are one of many signs that cyclonic storms are fairly frequent on
the borders of the ice though not in its interior. Thus there is a
distinct and sufficient form of precipitation actually at work near the
margin of the ice, or exactly where the thickness of the ice sheet would
lead us to expect.

Another consideration which throws grave doubt on the anti-cyclonic
hypothesis of ice sheets is the small amount of moisture possible in the
highs because of their low temperature. Suppose, for the sake of
argument, that the temperature in the middle of an ice sheet averages
20 deg.F. This is probably much higher than the actual fact and therefore
unduly favorable to the anti-cyclonic hypothesis. Suppose also that the
decrease in temperature from the earth's surface upward proceeds at the
rate of 1 deg.F. for each 300 feet, which is 50 per cent less than the
actual rate for air with only a slight amount of moisture, such as is
found in cold regions. Then at a height of 10,000 feet, where the
inblowing winds begin to be felt, the temperature would be -20 deg.F. At
that temperature the air is able to hold approximately 0.166 grain of
moisture per cubic foot when fully saturated. This is an exceedingly
small amount of moisture and even if it were all precipitated could
scarcely build a glacier. However, it apparently would not be
precipitated because when such air descends in the center of the
anti-cyclone it is warmed adiabatically, that is, by compression. On
reaching the surface it would have a temperature of 20 deg. and would be
able to hold 0.898 grain of water vapor per cubic foot; in other words,
it would have a relative humidity of about 18 per cent. Under no
reasonable assumption does the upper air at the center of an ice sheet
appear to reach the surface with a relative humidity of more than 20 or
25 per cent. Such air cannot give up moisture. On the contrary, it
absorbs it and tends to diminish rather than increase the thickness of
the sheet of ice and snow. But after the surplus heat gained by descent
has been lost by radiation, conduction, and evaporation, the air may
become super-saturated with the moisture picked up while warm. Hobbs
reports that explorers in Antarctica and Greenland have frequently
observed condensation on their clothing. If such moisture is not derived
directly from the men's own bodies, it is apparently picked up from the
ice sheet by the descending air, and not added to the ice sheet by air
from aloft.

The relation of all this to the localization of ice sheets is this. If
Hobbs' anti-cyclonic hypothesis of glacial growth is correct, it would
appear that ice sheets should grow up where the temperature is lowest
and the high-pressure areas most persistent; for instance, in northern
Siberia. It would also appear that so far as the topography permitted,
the ice sheets ought to move out uniformly in all directions; hence the
ice sheet ought to be as prominent to the north of the Keewatin and
Labradorean centers as to the south, which is by no means the case.
Again, in mountainous regions, such as the glacial areas of Alaska and
Chile, the glaciation ought not to be confined to the windward slope of
the mountains so closely as is actually the fact. In each of these cases
the glaciated region was large enough so that there was probably a true
anti-cyclonic area comparable with that now prevailing over southern
Greenland. In both places the correlation between glaciation and
mountain ranges seems much too close to support the anti-cyclonic
hypothesis, for the inblowing winds which on that hypothesis bring the
moisture are shown by observation to occur at heights far greater than
that of all but the loftiest ranges.

II. The sudden coming of glaciation is another problem which has been a
stumbling-block in the way of every glacial hypothesis. In his Climates
of Geologic Times, Schuchert states that the fossils give almost no
warning of an approaching catastrophe. If glaciation were solely due to
uplift, or other terrestrial changes aside from vulcanism, Schuchert
holds that it would have come slowly and the stages preceding glaciation
would have affected life sufficiently to be recorded in the rocks. He
considers that the suddenness of the coming of glaciation is one of the
strongest arguments against the carbon dioxide hypothesis of glaciation.

According to the cyclonic hypothesis, however, the suddenness of the
oncoming of glaciation is merely what would be expected on the basis of
what happens today. Changes in the sun occur suddenly. The sunspot cycle
is only eleven or twelve years long, and even this short period of
activity is inaugurated more suddenly than it declines. Again the
climatic record derived from the growth of trees, as given in Figs. 4
and 5, also shows that marked changes in climate are initiated more
rapidly than they disappear. In this connection, however, it must be
remembered that solar activity may arise in various ways, as will appear
more fully later. Under certain conditions storminess may increase and
decrease slowly.

III. The height of the snow line and of glaciation furnishes another
means of testing glacial hypotheses. It is well established that in
times of glaciation the snow line was depressed everywhere, but least
near the equator. For example, according to Penck, permanent snow
extended 4000 feet lower than now in the Alps, whereas it stood only
1500 feet below the present level near the equator in Venezuela. This
unequal depression is not readily accounted for by any hypothesis
depending solely upon the lowering of temperature. By the carbon dioxide
and the volcanic dust hypotheses, the temperature presumably was lowered
almost equally in all latitudes, but a little more at the equator than
elsewhere. If glaciation were due to a temporary lessening of the
radiation received from the sun, such as is demanded by the thermal
solar hypothesis, and by the longer periods of Croll's hypothesis, the
lowering would be distinctly greatest at the equator. Thus, according to
all these hypotheses, the snow line should have been depressed most at
the equator, instead of least.

The cyclonic hypothesis explains the lesser depression of the snow line
at the equator as due to a diminution of precipitation. The
effectiveness of precipitation in this respect is illustrated by the
present great difference in the height of the snow line on the humid and
dry sides of mountains. On the wet eastern side of the Andes near the
equator, the snow line lies at 16,000 feet; on the dry western side, at
18,500 feet. Again, although the humid side of the Himalayas lies toward
the south, the snow line has a level of 15,000 feet, while farther
north, on the dry side, it is 16,700 feet.[47] The fact that the snow
line is lower near the margin of the Alps than toward the center points
in the same direction. The bearing of all this on the glacial period may
be judged by looking again at Fig. 3 in Chapter V. This shows that at
times of sunspot activity and hence of augmented storminess, the
precipitation diminishes near the heat equator, that is, where the
average temperature for the whole year is highest. At present the great
size of the northern continents and their consequent high temperature in
summer, cause the heat equator to lie north of the "real" equator,
except where Australia draws it to the southward.[48] When large parts
of the northern continents were covered with ice, however, the heat
equator and the true equator were probably much closer than now, for the
continents could not become so hot. If so, the diminution in equatorial
precipitation, which accompanies increased storminess throughout the
world as a whole, would take place more nearly along the true equator
than appears in Fig. 3. Hence so far as precipitation alone is
concerned, we should actually expect that the snow line near the equator
would rise a little during glacial periods. Another factor, however,
must be considered. Koeppen's data, it will be remembered, show that at
times of solar activity the earth's temperature falls more at the
equator than in higher latitudes. If this effect were magnified it would
lower the snow line. The actual position of the snow line at the equator
during glacial periods thus appears to be the combined effect of
diminished precipitation, which would raise the line, and of lower
temperature, which would bring it down.

Before leaving this subject it may be well to recall that the relative
lessening of precipitation in equatorial latitudes during the glacial
epochs was probably caused by the diversion of moisture from the
trade-wind belt. This diversion was presumably due to the great number
of tropical cyclones and to the fact that the cyclonic storms of middle
latitudes also drew much moisture from the trade-wind belt in summer
when the northern position of the sun drew that belt near the storm
track which was forced to remain south of the ice sheet. Such diversion
of moisture out of the trade-wind belt must diminish the amount of water
vapor that is carried by the trades to equatorial regions; hence it
would lessen precipitation in the belt of so-called equatorial calms,
which lies along the heat equator rather than along the geographical
equator.

Another phase of the vertical distribution of glaciation has been the
subject of considerable discussion. In the Alps and in many other
mountains the glaciation of the Pleistocene period appears to have had
its upper limit no higher than today. This has been variously
interpreted. It seems, however, to be adequately explained as due to
decreased precipitation at high altitudes during the cold periods. This
is in spite of the fact that precipitation in general increased with
increased storminess. The low temperature of glacial times presumably
induced condensation at lower altitudes than now, and most of the
precipitation occurred upon the lower slopes of the mountains,
contributing to the lower glaciers, while little of it fell upon the
highest glaciers. Above a moderate altitude in all lofty mountains the
decrease in the amount of precipitation is rapid. In most cases the
decrease begins at a height of less than 3000 feet above the base of the
main slope, provided the slope is steep. The colder the air, the lower
the altitude at which this occurs. For example, it is much lower in
winter than in summer. Indeed, the higher altitudes in the Alps are
sunny in winter even where there are abundant clouds lower down.

IV. The presence of extensive lakes and other evidences of a pluvial
climate during glacial periods in non-glaciated regions which are
normally dry is another of the facts which most glacial hypotheses fail
to explain satisfactorily. Beyond the ice sheets many regions appear to
have enjoyed an unusually heavy precipitation during the glacial epochs.
The evidence of this is abundant, including numerous abandoned strand
lines of salt lakes and an abundance of coarse material in deltas and
flood plains. J. D. Whitney,[49] in an interesting but neglected volume,
was one of the first to marshal the evidence of this sort. More recently
Free[50] has amplified this. According to him in the Great Basin region
of the United States sixty-two basins either contain unmistakable
evidence of lakes, or belong to one of the three great lake groups named
below. Two of these, the Lake Lahontan and the Lake Bonneville groups,
comprise twenty-nine present basins, while the third, the Owens-Searles
chain, contained at least five large lakes, the lowest being in Death
Valley. In western and central Asia a far greater series of salt lakes
is found and most of these are surrounded by strands at high levels.
Many of these are described in Explorations in Turkestan, The Pulse
of Asia, and Palestine and Its Transformation. There has been a good
deal of debate as to whether these lakes actually date from the glacial
period, as is claimed by C. E. P. Brooks, for example, or from some
other period. The evidence, however, seems to be convincing that the
lakes expanded when the ice also expanded.

According to the older glacial hypotheses the lower temperature which is
postulated as the cause of glaciation would almost certainly mean less
evaporation over the oceans and hence less precipitation during glacial
periods. To counteract this the only way in which the level of the lakes
could be raised would be because the lower temperature would cause less
evaporation from their surfaces. It seems quite impossible, however,
that the lowering of temperature, which is commonly taken to have been
not more than 10 deg.C., could counteract the lessened precipitation and
also cause an enormous expansion of most of the lakes. For example,
ancient Lake Bonneville was more than ten times as large as its modern
remnant, Great Salt Lake, and its average depth more than forty times as
great.[51] Many small lakes in the Old World expanded still more.[52]
For example, in eastern Persia many basins which now contain no lake
whatever are floored with vast deposits of lacustrine salt and are
surrounded by old lake bluffs and beaches. In northern Africa similar
conditions prevail.[53] Other, but less obvious, evidence of more
abundant rainfall in regions that are now dry is found in thick strata
of gravel, sand, and fine silt in the alluvial deposits of flood plains
and deltas.[54]

The cyclonic hypothesis supposes that increased storminess accounts for
pluvial climates in regions that are now dry just as it accounts for
glaciation in the regions of the ice sheets. Figs. 2 and 3, it will be
remembered, illustrate what happens when the sun is active. Solar
activity is accompanied by an increase in storminess in the southwestern
United States in exactly the region where elevated strands of diminished
salt lakes are most numerous. In Fig. 3, the same condition is seen in
the region of salt lakes in the Old World. Judging by these maps, which
illustrate what has happened since careful meteorological records were
kept, an increase in solar activity is accompanied by increased rainfall
in large parts of what are now semi-arid and desert regions. Such
precipitation would at once cause the level of the lakes to rise. Later,
when ice sheets had developed in Europe and America, the high-pressure
areas thus caused might force the main storm belt so far south that it
would lie over these same arid regions. The increase in tropical
hurricanes at times of abundant sunspots may also have a bearing on the
climate of regions that are now arid. During the glacial period some of
the hurricanes probably swept far over the lands. The numerous tropical
cyclones of Australia, for example, are the chief source of
precipitation for that continent.[55] Some of the stronger cyclones
locally yield more rain in a day or two than other sources yield in a
year.

V. The occurrence of widespread glaciation near the tropics during the
Permian, as shown in Fig. 7, has given rise to much discussion. The
recent discovery of glaciation in latitudes as low as 30 deg. in the
Proterozoic is correspondingly significant. In all cases the occurrence
of glaciation in low and middle latitudes is probably due to the same
general causes. Doubtless the position and altitude of the mountains had
something to do with the matter. Yet taken by itself this seems
insufficient. Today the loftiest range in the world, the Himalayas, is
almost unglaciated, although its southern slope may seem at first
thought to be almost ideally located in this respect. Some parts rise
over 20,000 feet and certain lower slopes receive 400 inches of rain per
year. The small size of the Himalayan glaciers in spite of these
favorable conditions is apparently due largely to the seasonal character
of the monsoon winds. The strong outblowing monsoons of winter cause
about half the year to be very dry with clear skies and dry winds from
the interior of Asia. In all low latitudes the sun rides high in the
heavens at midday, even in winter, and thus melts snow fairly
effectively in clear weather. This is highly unfavorable to glaciation.
The inblowing southern monsoons bring all their moisture in midsummer at
just the time when it is least effective in producing snow. Conditions
similar to those now prevailing in the Himalayas must accompany any
great uplift of the lands which produces high mountains and large
continents in subtropical and middle latitudes. Hence, uplift alone
cannot account for extensive glaciation in subtropical latitudes during
the Permian and Proterozoic.


(After Schuchert.)]

The assumption of a great general lowering of temperature is also not
adequate to explain glaciation in subtropical latitudes. In the first
place this would require a lowering of many degrees,--far more than in
the Pleistocene glacial period. The marine fossils of the Permian,
however, do not indicate any such condition. In the second place, if the
lands were widespread as they appear to have been in the Permian, a
general lowering of temperature would diminish rather than increase the
present slight efficiency of the monsoons in producing glaciation.
Monsoons depend upon the difference between the temperatures of land and
water. If the general temperature were lowered, the reduction would be
much less pronounced on the oceans than on the lands, for water tends to
preserve a uniform temperature, not only because of its mobility, but
because of the large amount of heat given out when freezing takes place,
or consumed in evaporation. Hence the general lowering of temperature
would make the contrast between continents and oceans less than at
present in summer, for the land temperature would be brought toward that
of the ocean. This would diminish the strength of the inblowing summer
monsoons and thus cut off part of the supply of moisture. Evidence that
this actually happened in the cold fourteenth century has already been
given in Chapter VI. On the other hand, in winter the lands would be
much colder than now and the oceans only a little colder, so that the
dry outblowing monsoons of the cold season would increase in strength
and would also last longer than at present. In addition to all this, the
mere fact of low temperature would mean a general reduction in the
amount of water vapor in the air. Thus, from almost every point of view
a mere lowering of temperature seems to be ruled out as a cause of
Permian glaciation. Moreover, if the Permian or Proterozoic glacial
periods were so cold that the lands above latitude 30 deg. were snow-covered
most of the time, the normal surface winds in subtropical latitudes
would be largely equatorward, just as the winter monsoons now are. Hence
little or no moisture would be available to feed the snowfields which
give rise to the glaciers.

It has been assumed by Marsden Manson and others that increased general
cloudiness would account for the subtropical glaciation of the Permian
and Proterozoic. Granting for the moment that there could be universal
persistent cloudiness, this would not prevent or counteract the
outblowing anti-cyclonic winds so characteristic of great snowfields.
Therefore, under the hypothesis of general cloudiness there would be no
supply of moisture to cause glaciation in low latitudes. Indeed,
persistent cloudiness in all higher latitudes would apparently deprive
the Himalayas of most of their present moisture, for the interior of
Asia would not become hot in summer and no inblowing monsoons would
develop. In fact, winds of all kinds would seemingly be scarce, for they
arise almost wholly from contrasts of temperature and hence of
atmospheric pressure. The only way to get winds and hence precipitation
would be to invoke some other agency, such as cyclonic storms, but that
would be a departure from the supposition that glaciation arose from
cloudiness.

Let us now inquire how the cyclonic hypothesis accounts for glaciation
in low latitudes. We will first consider the terrestrial conditions in
the early Permian, the last period of glaciation in such latitudes.
Geologists are almost universally agreed that the lands were
exceptionally extensive and also high, especially in low latitudes. One
evidence of this is the presence of abundant conglomerates composed of
great boulders. It is also probable that the carbon dioxide in the air
during the early Permian had been reduced to a minimum by the
extraordinary amount of coal formed during the preceding period. This
would tend to produce low temperature and thus make the conditions
favorable for glaciation as soon as an accentuation of solar activity
caused unusual storminess. If the storminess became extreme when
terrestrial conditions were thus universally favorable to glaciation, it
would presumably produce glaciation in low latitudes. Numerous and
intense tropical cyclones would carry a vast amount of moisture out of
the tropics, just as now happens when the sun is active, but on a far
larger scale. The moisture would be precipitated on the equatorward
slopes of the subtropical mountain ranges. At high elevations this
precipitation would be in the form of snow even in summer. Tropical
cyclones, however, as is shown in Earth and Sun, occur in the autumn
and winter as well as in summer. For example, in the Bay of Bengal the
number recorded in October is fifty, the largest for any month; while in
November it is thirty-four, and December fourteen as compared with an
average of forty-two for the months of July to September. From January
to March, when sunspot numbers averaged more than forty, the number of
tropical hurricanes was 143 per cent greater than when the sunspot
numbers averaged below forty. During the months from April to June,
which also would be times of considerable snowy precipitation, tropical
hurricanes averaged 58 per cent more numerous with sunspot numbers above
forty than with numbers below forty, while from July to September the
difference amounted to 23 per cent. Even at this season some snow falls
on the higher slopes, while the increased cloudiness due to numerous
storms also tends to preserve the snow. Thus a great increase in the
frequency of sunspots is accompanied by increased intensity of tropical
hurricanes, especially in the cooler autumn and spring months, and
results not only in a greater accumulation of snow but in a decrease in
the melting of the snow because of more abundant clouds. At such times
as the Permian, the general low temperature due to rapid convection and
to the scarcity of carbon dioxide presumably joined with the extension
of the lands in producing great high-pressure areas over the lands in
middle latitudes during the winters, and thus caused the more northern,
or mid-latitude type of cyclonic storms to be shifted to the equatorward
side of the continents at that season. This would cause an increase of
precipitation in winter as well as during the months when tropical
hurricanes abound. Many other circumstances would cooeperate to produce a
similar result. For example, the general low temperature would cause the
sea to be covered with ice in lower latitudes than now, and would help
to create high-pressure areas in middle latitudes, thus driving the
storms far south. If the sea water were fresher than now, as it probably
was to a notable extent in the Proterozoic and perhaps to some slight
extent in the Permian, the higher freezing point would also further the
extension of the ice and help to keep the storms away from high
latitudes. If to this there is added a distribution of land and sea such
that the volume of the warm ocean currents flowing from low to high
latitudes was diminished, as appears to have been the case, there seems
to be no difficulty in explaining the subtropical location of the main
glaciation in both the Permian and the Proterozoic. An increase of
storminess seems to be the key to the whole situation.

One other possibility may be mentioned, although little stress should be
laid on it. In Earth and Sun it has been shown that the main storm
track in both the northern and southern hemispheres is not concentric
with the geographical poles. Both tracks are roughly concentric with the
corresponding magnetic poles, a fact which may be important in
connection with the hypothesis of an electrical effect of the sun upon
terrestrial storminess. The magnetic poles are known to wander
considerably. Such wandering gives rise to variations in the direction
of the magnetic needle from year to year. In 1815 the compass in England
pointed 24-1/2 deg. W. of N. and in 1906 17 deg. 45' W. Such a variation seems
to mean a change of many miles in the location of the north magnetic
pole. Certain changes in the daily march of electromagnetic phenomena
over the oceans have led Bauer and his associates to suggest that the
magnetic poles may even be subject to a slight daily movement in
response to the changes in the relative positions of the earth and sun.
Thus there seems to be a possibility that a pronounced change in the
location of the magnetic pole in Permian times, for example, may have
had some connection with a shifting in the location of the belt of
storms. It must be clearly understood that there is as yet no evidence
of any such change, and the matter is introduced merely to call
attention to a possible line of investigation.

Any hypothesis of Permian and Proterozoic glaciation must explain not
only the glaciation of low latitudes but the lack of glaciation and the
accumulation of red desert beds in high latitudes. The facts already
presented seem to explain this. Glaciation could not occur extensively
in high latitudes partly because during most of the year the air was too
cold to hold much moisture, but still more because the winds for the
most part must have blown outward from the cold northern areas and the
cyclonic storm belt was pushed out of high latitudes. Because of these
conditions precipitation was apparently limited to a relatively small
number of storms during the summer. Hence great desert areas must have
prevailed at high latitudes. Great aridity now prevails north of the
Himalayas and related ranges, and red beds are accumulating in the
centers of the great deserts, such as those of the Tarim Basin and the
Transcaspian. The redness is not due to the original character of the
rock, but to intense oxidation, as appears from the fact that along the
edges of the desert and wherever occasional floods carry sediment far
out into the midst of the sand, the material has the ordinary brownish
shades. As soon as one goes out into the places where the sand has been
exposed to the air for a long time, however, it becomes pink, and then
red. Such conditions may have given rise to the high degree of oxidation
in the famous Permian red beds. If the air of the early Permian
contained an unusual percentage of oxygen because of the release of that
gas by the great plant beds which formed coal in the preceding era, as
Chamberlin has thought probable, the tendency to produce red beds would
be still further increased.

It must not be supposed, however, that these conditions would absolutely
limit glaciation to subtropical latitudes. The presence of early Permian
glaciation in North America at Boston and in Alaska and in the Falkland
Islands of the South Atlantic Ocean proves that at least locally there
was sufficient moisture to form glaciers near the coast in relatively
high latitudes. The possibility of this would depend entirely upon the
form of the lands and the consequent course of ocean currents. Even in
those high latitudes cyclonic storms would occur unless they were kept
out by conditions of pressure such as have been described above.

The marine faunas of Permian age in high latitudes have been interpreted
as indicating mild oceanic temperatures. This is a point which requires
further investigation. Warm oceans during times of slight solar activity
are a necessary consequence of the cyclonic hypothesis, as will appear
later. The present cold oceans seem to be the expectable result of the
Pleistocene glaciation and of the present relatively disturbed condition
of the sun. If a sudden disturbance threw the solar atmosphere into
violent commotion within a few thousand years during Permian times,
glaciation might occur as described above, while the oceans were still
warm. In fact their warmth would increase evaporation while the violent
cyclonic storms and high winds would cause heavy rain and keep the air
cool by constantly raising it to high levels where it would rapidly
radiate its heat into space.

Nevertheless it is not yet possible to determine how warm the oceans
were at the actual time of the Permian glaciation. Some faunas formerly
reported as Permian are now known to be considerably older. Moreover,
others of undoubted Permian age are probably not strictly
contemporaneous with the glaciation. So far back in the geological
record it is very doubtful whether we can date fossils within the limits
of say 100,000 years. Yet a difference of 100,000 years would be more
than enough to allow the fossils to have lived either before or after
the glaciation, or in an inter-glacial epoch. One such epoch is known to
have occurred and nine others are suggested by the inter-stratification
of glacial till and marine sediments in eastern Australia. The warm
currents which would flow poleward in inter-glacial epochs must have
favored a prompt reintroduction of marine faunas driven out during times
of glaciation. Taken all and all, the Permian glaciation seems to be
accounted for by the cyclonic hypothesis quite as well as does the
Pleistocene. In both these cases, as well as in the various pulsations
of historic times, it seems to be necessary merely to magnify what is
happening today in order to reproduce the conditions which prevailed in
the past. If the conditions which now prevail at times of sunspot minima
were magnified, they would give the mild conditions of inter-glacial
epochs and similar periods. If the conditions which now prevail at times
of sunspot maxima are magnified a little they seem to produce periods of
climatic stress such as those of the fourteenth century. If they are
magnified still more the result is apparently glacial epochs like those
of the Pleistocene, and if they are magnified to a still greater extent,
the result is Permian or Proterozoic glaciation. Other factors must
indeed be favorable, for climatic changes are highly complex and are
unquestionably due to a combination of circumstances. The point which is
chiefly emphasized in this book is that among those several
circumstances, changes in cyclonic storms due apparently to activity of
the sun's atmosphere must always be reckoned.

FOOTNOTES:

[Footnote 46: W. H. Hobbs: Characteristics of Existing Glaciers, 1911.
The Role of the Glacial Anticyclones in the Air Circulation of the
Globe; Proc. Am. Phil. Soc., Vol. 54, 1915, pp. 185-225.]

[Footnote 47: R. D. Salisbury: Physiography, 1919.]

[Footnote 48: Griffith Taylor: Australian Meteorology, 1920, p. 283.]

[Footnote 49: J. D. Whitney: Climatic Changes of the Later Geological
Times, 1882.]

[Footnote 50: E. E. Free: U. S. Dept. of Agriculture, Bull. 54, 1914.
Mr. Free has prepared a summary of this Bulletin which appears in The
Solar Hypothesis, Bull. Geol. Sec. of Am., Vol. 25, pp. 559-562.]

[Footnote 51: G. K. Gilbert: Lake Bonneville; Monograph 1, U. S. Geol.
Surv.]

[Footnote 52: C. E. P. Brooks: Quart. Jour. Royal Meteorol. Soc., 1914,
pp. 63-66.]

[Footnote 53: H. J. L. Beadnell: A. Egyptian Oasis, London, 1909.
Ellsworth Huntington: The Libyan Oasis of Kharga; Bull. Am. Geog. Soc.,
Vol. 42, Sept., 1910, pp. 641-661.]

[Footnote 54: S. S. Visher: The Bajada of the Tucson Bolson of Southern
Arizona; Science, N. S., Mar. 23, 1913.

Ellsworth Huntington: The Basins of Eastern Persia and Seistan, in
Explorations in Turkestan.]

[Footnote 55: Griffith Taylor: Australian Meteorology, 1920, p. 189.]





Next: The Origin Of Loess

Previous: Glaciation According To The Solar-cyclonic Hypothesis[38]



Add to del.icio.us Add to Reddit Add to Digg Add to Del.icio.us Add to Google Add to Twitter Add to Stumble Upon
Add to Informational Site Network
Report
Privacy
SHAREADD TO EBOOK


Viewed 489