UC-NRLF
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WORLDS IN THE MAKING
THE EVOLUTION OF THE UNIVERSE
BY
SVANTE ARRHENIUS
IV
DIRECTOR OF THE PHYSICO-CHEMICAL NOBEL INSTITUTE, STOCKHOLM
TRANSLATED BY DR. H. BORNS
ILLUSTRATED
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NEW YORK AND LONDON
HARPER & BROTHERS PUBLISHERS
M C M V I I I
GENERAL
c 6X
U
Copyright, 1908, by HARPER & BROTHERS.
All rights reserved. Published March, 1908.
TABLE OF CONTENTS
I. VOLCANIC PHENOMENA AND EARTHQUAKES . . 1
Destruction caused by volcanism and by earthquakes. — Different kinds of volcanoes. — Vesuvius. — Products of erup- tion.— Volcanic activity diminishing. — Structure of vol- canoes.— Geographical distribution of volcanoes. — Tempera- ture in the interior of the earth. — Significance of water for volcanism. — Composition of the earth's interior. — Geo- graphical distribution of earthquakes. — Fissures in the earth's crust. — Groups of earthquakes. — Waves in the sea and in the air accompanying earthquakes. — Their connec- tion with volcanism. — Systems of fissures. — Seismograms.
II. THE CELESTIAL BODIES, IN PARTICULAR THE
EARTH, AS ABODES OF LIVING BEINGS ... 39 ^
Manifold character of the worlds. — The earth probably at first a ball of gases. — Formation of the earth crust and its rapid cooling. — Balance between heat received and heat lost' by radiation. — Life already existing on the earth for a milliard of years. — The waste of solar heat. — Temperature and habitability of the planets. — Heat-preserving influence of the atmosphere. — Significance of carbon dioxide in the atmosphere — Warm and cold geological ages. — Fluctua- tions in the percentage of carbon dioxide of the air. — Com- bustion, decay, and growth. — Atmospheric oxygen. — Vege- table life more ancient than animal life. — The atmospheres of planets. — Chances of an improvement in the climate.
III. RADIATION AND CONSTITUTION OF THE SUN . 64
Stability of the solar system. — Losses and possible gains of heat by the sun. — Theses of Mayer and of Helmholtz. — Temperatures of the white, yellow, and reddish stars, and of the sun. — Sun-spots and sun faculse. — Prominences. —
TABLE OF CONTENTS
Spectra of the parts of the sun. — Temperature of the sun. — The interior of the sun. — Its composition according to the mechanical theory of heat. — The losses of heat by the sun probably covered by the enormous solar energy.
IV. THE RADIATION PRESSURE 94
Newton's law of gravitation. — Kepler's observation of comets' tails. — The thesis of Euler. — Proof of Maxwell. — The radiation pressure. — Electric charges and condensa- tion.— Comets' tails and radiation pressure. — Constituents and properties of comets' tails. — Weight of the solar corona. — Loss and gain of matter by the sun. — Nature of meteor- ites.— Electric charge of the sun. — Electrons drawn into the sun. — Magnetic properties of the sun and appearance of the corona. — Constituents of the meteors. — Nebulae and their heat and light.
V. THE SOLAR DUST IN THE ATMOSPHERE. POLAR
LIGHTS AND THE VARIATIONS OF TERRES- TRIAL MAGNETISM 118
The supply of dust from the sun rather insignificant. — Polarization of the light of the sky. — The upper clouds. — Different kinds of aurorse. — Their connection with the corona of the sun. — Polar lights and sun-spots — Periodicity of polar lights. — Polar lights and magnetic disturbances. — Velocity of solar dust. — -Fixation of atmospheric nitrogen.— The Zodiacal Light.
VI. END OF THE SUN.— ORIGIN OF NEBULA ... 148
The extinction of the sun. — Collision between two celestial bodies. — The new star in Perseus. — Formation of nebulae. — The appearance of nebulae. — The nebulae catch wandering meteors and comets. — The ring nebula in Lyra. — Variable stars. — Eta in Argus. — Mira Ceti. — Lyra and Algol stars. — Evolution of the stars.
VII. THE NEBULAR AND THE SOLAR STATES . .191
The energy of the universe. — The entropy of the universe. — The entropy increases in the suns, but decreases in the nebulae. — Temperature and constitution of the nebulae. — Schuster's calculations of the condition of a celestial body consisting of gases. — Action of the loss of heat on nebulae iv
TABLE OF CONTENTS
and on suns. — Development of a rotating nebula into a planetary system. — The hypothesis of Kant-Laplace. — Ob- jections to it. — The views of Chamberlin and Moulton. — The radiation pressure balances the effect of Newtonian gravitation. — The emission of gases from the nebulae bal- ances the waste of heat characteristic to the solar systems.
VIII. THE SPREADING OF LIFE THROUGH THE
UNIVERSE ... ............ 212
Stability of the species. — Theory of mutation. — Sponta- neous generation. — Bathybius. — Panspermia. — The stand- points of Richter, Ferdinand Cohn, and Lord Kelvin. — The radiation pressure enables spores to escape. — The effect of strong sunlight and of cold on the germinating power. — Transport of spores through the atmosphere into universal space and through it to other planets. — General conclusions.
EXPLANATION OF ABBREVIATIONS, ETC.
The temperatures are stated in degrees centigrade (° C.), either on the Celsius scale, on which the freezing-point of water is O°, or on the absolute scale, whose zero lies 273 degrees below the freezing- point of water, at —273° C. The equivalent temperatures on the Fahrenheit scale (freezing-point of water 32° F.) are added in brackets (° F.).
1 metre (m.) =10 decimetres (dm.) =100 centimetres (cm.) =1000
millimetres (mm.) =3.28 ft.; 1 kilometre (km.) =1000 metres (rn.) ^v = 1.6 miles ; 1 mile =0.62 kilometres (km.).
Light travels in yacuo at the rate of 300,000 km. (nearly 200,000 miles) per second.
ILLUSTRATIONS
PAGE
1. VESUVIUS, AS SEEN FROM THE ISLAND OP NISIDA, IN
MODERATE ACTIVITY ........ .... 2
2. ERUPTION OF VESUVIUS IN 1882 ...... .... 4
3. ERUPTION OF VESUVIUS IN 1872 .......... 6
4. PHOTOGRAPH OF VESUVIUS, 1906. CHIEFLY CLOUDS OF
ASHES ........... . ..... 8
5. BLOCK LAVA ON MAUNA LOA .......... 10
6. THE EXCELSIOR GEYSER IN YELLOWSTONE PARK, U. S. A.
REMNANT OF POWERFUL VOLCANIC ACTIVITY IN THE TERTIARY AGE .............. 11
7. MATO TEPEE IN WYOMING, U. S. A. TYPICAL VOLCANIC
"NECK" ................ 12
8. CLEFTS FILLED WITH LAVA AND VOLCANIC CONE OF ASHES,
TOROWHEAP CANON, PLATEAU OF COLORADO .... 13
9. THE KILAUEA CRATER ON HAWAII ......... 15
10. CHIEF EARTHQUAKE CENTRES, ACCORDING TO THE BRITISH
ASSOCIATION COMMITTEE ......... . 22
11. CLEFTS IN VALENTIA STREET, SAN FRANCISCO, AFTER THE
EARTHQUAKE OF 1906 ........... 25
12. SAND CRATERS AND FISSURES, PRODUCED BY THE CORINTH
EARTHQUAKE OF 1861. IN THE WATER, BRANCHES OF FLOODED TREES ............. 27
13. EARTHQUAKE LINES IN LOWER AUSTRIA ....... 30
14. LIBERTY BUILDING OF LELAND STANFORD JUNIOR UNIVER-
SITY, IN CALIFORNIA, AFTER THE EARTHQUAKE OF 1906 32
15. EARTHQUAKE LINES IN THE TYRRHENIAN DEPRESSION . . 34
vii
ILLUSTRATIONS
FIG. PAGE
16. SEISMOGRAM RECORDED AT SHIDE, ISLE OF WIGHT, ON
AUGUST 31, 1898 35
17. PHOTOGRAPH OF THE SURFACE OF THE MOON, IN THE VICIN-
ITY OF THE CRATER OF COPERNICUS 62
18. SUN-SPOT GROUP AND GRANULATION OF THE SUN ... 74
19. PART OF THE SOLAR SPECTRUM OF JANUARY 3, 1872 . . 75
20. METALLIC PROMINENCES IN VORTEX MOTION 76
21. FOUNTAIN-LIKE METALLIC PROMINENCES 76
22. QUIET PROMINENCES OF SMOKE-COLUMN TYPE ..... 77
23. QUIET PROMINENCES, SHAPE OF A TREE 77
24. DIAGRAM ILLUSTRATING THE DIFFERENCES IN THE SPECTRA '
OF SUN-SPOTS AND OF THE PHOTOSPHERE 78
25. SPECTRUM OF A SUN-SPOT, THE CENTRAL BAND BETWEEN
THE TWO PORTIONS OF THE PHOTOSPHERES PECTRUM . 78
26. THE GREAT SUN-SPOT OF OCTOBER 9, 1903 79
27. THE GREAT SUN-SPOT OF OCTOBER 9, 1903 ...... 80
28. THE GREAT SUN-SPOT OF OCTOBER 9, 1903 81
29. THE GREAT SUN-SPOT OF OCTOBER 9, 1903 82
30. PHOTOGRAPH OF THE SOLAR CORONA OF 1900 83
31. PHOTOGRAPH OF THE SOLAR CORONA OF 1870 84
32. PHOTOGRAPH OF THE SOLAR CORONA OF 1898 85
33. PHOTOGRAPH OF ROERDAM's COMET (1893 II.), SUGGESTING
SEVERAL STRONG NUCLEI IN THE TAIL 100
34. PHOTOGRAPH OF SWIFT'S COMET (1892 I.) 101
35. DONATI'S COMET AT ITS GREATEST BRILLIANCY IN 1858 . 102
36. IMITATION OF COMETS' TAILS 104
37. GRANULAR CHONDRUM FROM THE METEORITE OF SEXES.
ENLARGEMENT 1 : 70 109
38. ARCH-SHAPED AURORA BOREALIS, OBSERVED BY NORDEN-
SKIOLD DURING THE WINTERING OF THE VEGA IN
BERING STRAIT, 1879 124
39. AURORA BOREALIS, WITH RADIAL STREAMERS 125
40. AURORA WITH CORONA, OBSERVED BY GYLLENSKIOLD ON
SPITZBERGEN, 1883 126
V viii
ILLUSTRATIONS
FIO. PAGE
41. POLAR-LIGHT DRAPERIES, OBSERVED IN FINNMARKEN, NORTH-
ERN NORWAY 127
42. CURVE OF MAGNETIC DECLINATION AT KEW, NEAR LONDON,
ON NOVEMBER 15 AND 16, 1905 138
43. CURVE OF HORIZONTAL INTENSITY AT KEW ON NOVEMBER
15 AND 16, 1905 139
44. ZODIACAL LIGHT IN THE TROPICS 146
45. SPECTRUM OF NOVA AURIGA, 1892 . 154
46. DIAGRAM INDICATING THE CONSEQUENCES OF A COLLISION
BETWEEN TWO EXTINCT SUNS .157
47. SPIRAL NEBULA IN THE CANES VENATICI 159
48. SPIRAL NEBULA IN THE TRIANGLE v . . . 161
49. THE GREAT NEBULA IN ANDROMEDA . 163
50. RING-SHAPED NEBULA IN LYRA 164
51. CENTRAL PORTION OF THE GREAT NEBULA IN ORION . . . 165
52. NEBULAR STRLE IN THE STARS OF THE PLEIADES .... 167
53. NEBULAR STRLE IN THE SWAN 169
54. NEBULA AND STAR RIFT IN THE SWAN, IN THE MILKY WAY 171
55. GREAT NEBULA NEAR RHO, IN OPHIUCHUS 172
56. STAR CLUSTER IN HERCULES 173
57. STAR' CLUSTER IN PEGASUS 175
58. CONE-SHAPED STAR CLUSTER IN GEMINI 176
59. COMPARISON OF SPECTRA OF STARS OF CLASSES 2, 3, 4 . 185
60. COMPARISON OF SPECTRA OF STARS OF CLASSES 2, 3, 4 . 186
PREFACE
WHEN, more than six years ago, I was writing my Treatise of Cosmic Physics, I found myself confronted with great difficulties. The views then held would not explain many phenomena, and they failed in particular in cosmogonic problems. The radiation pressure of light, which had not, so far, been heeded, seemed to% give me the key to the elucidation of many obscure problems, and I made a large use of this force in dealing with those phenomena in my treatise.
The explanations which I tentatively offered could, of course, not claim to stand in all their detail; yet the scientific world received them with unusual interest and benevolence. Thus encouraged, I tried to solve more of the numerous important problems, and in the present volume I have added some further sections to the com- plex of explanatory arguments concerning the evolution of the Universe. The foundation to these explanations was laid in a memoir which I presented to the Academy of Sciences at Stockholm in 1900. The memoir was soon afterwards printed in the Physikalische Zeitschrift, and the subject was further developed in my Treatise of Cosmic Physics.
It will be objected, and not without justification, that scientific theses should first be discussed and approved of in competent circles before they are placed before the public. It cannot be denied that, if this condition were
xi
PREFACE
to be fulfilled, most of the suggestions on cosmogony that have been published would never have been sent to the compositors; nor do I deny that the labor spent upon their publication might have been employed for some better purpose. But several years have elapsed since my first attempts in this direction were communicated to scien- tists. My suggestions have met with a favorable recep- tion, and I have, during these years, had ample op- portunity carefully to re-examine and to amend my explanations. I therefore feel justified in submitting my views to a larger circle of readers.
The problem of the evolution of the Universe has al- ways excited the profound interest of thinking men. And it will, without doubt, remain the most eminent among all the questions which do not have any direct, practical bearing. Different ages have arrived at different solu- tions to this great problem. Each of these solutions re- flected the stand-point of the natural philosophers of its time. Let me hope that the considerations which I offer will be worthy of the grand progress in physics and chem- istry that has marked the close of the nineteenth and the opening of the twentieth century.
Before the indestructibility of energy was understood, cosmogony merely dealt with the question how matter could have been arranged in such a manner as to give rise to the actual worlds. The most remarkable con- ception of this kind we find in Herschel's suggestion of the evolution of stellar nebulae, and in the thesis of La- place concerning the formation of the solar system out of the universal nebula. Observations more and more tend to confirm Herschel's view. The thesis of Laplace, for a long time eulogized as the flower of cosmogonic speculations, has more and more had to be modified. If we attempt, with Kant, to conceive how wonderfully
xii
PREFACE
organized stellar systems could originate from absolute chaos, we shall have to admit that we are attacking a problem which is insoluble in that shape. There is a contradiction in those very attempts to explain the origin of the Universe in its totality, as Stallo1 emphasizes: " The only question to which a series of phenomena gives legitimate rise relates to their filiation and interdepend- ence." I have, therefore, only endeavored to show how nebulae may originate from suns and suns from nebulae; and I assume that this change has always been proceed- ing as it is now.
The recognition of the indestructibility of energy seemed to accentuate the difficulties of the cosmogonic problems. The theses of Mayer and of Helmholtz, on the manner in which the Sun replenishes its losses of heat, have had to be abandoned. My explanation is based upon chemical reactions in the interior of the Sun in accordance with the second law of thermodynamics. The theory of the "degradation" of energy appeared to introduce a still greater difficulty. That theory seems to lead to the inevitable conclusion that the Universe is tending towards the state which Clausius has desig- nated as " Wdrme Tod" (heat death), when all the energy of the Universe will uniformly be distributed through space in the shape of movements of the smallest particles. That would imply an absolutely inconceivable end of the development of the Universe. The way out of this diffi- culty which I propose comes to this: the energy is " de- graded" in bodies which are in the solar state, and the energy is "elevated," raised to a higher level, in bodies which are in the nebular state.
Finally, I wish to touch upon one cosmogonical ques-
1 Stallo : Concepts and Theories of Modern Physics. London, 1900, p. 276.
xiii
PREFACE
tion which has recently become more actual than it used to be. Some kind of "spontaneous generation," origina- tion of life from inorganic matter, had been acquiesced in. But just as the dreams of a spontaneous generation of energy — i.e., of a perpetuum mobile — have been dispelled by the negative results of all experiments in that direction, just in the same way we shall have to give up the idea of a spontaneous generation of life after all the repeated disappointments in this field of investigation. As Helmholtz1 says, in his popular lecture on the growth of the planetary system (1871) : " It seems to me a per- fectly just scientific procedure, if we, after the failure of all our attempts to produce organisms from lifeless matter, put the question, whether life has had a beginning at all, or whether it is not as old as matter, and whether seeds have not been carried from one planet to another and have developed everywhere where they have fallen on a fertile soil."
This hypothesis is called the hypothesis of panspermia, which I have modified by combining it with the thesis of the radiation pressure.
My guiding principle in this exposition of cosmogonic problems has been the conviction that the Universe in its essence has always been what it is now. Matter, en- ergy, and lifs have only varied as to shape and position in space.
THE AUTHOB.
STOCKHOLM, December, 1907.
1 Helmholtz, Popular^ Wissenschaftliche Vortrage. Braunschweig, 1876, vol. iii., p. 101.
WORLDS IN THE MAKING
VOLCANIC PHENOMENA AND EARTHQUAKES The Interior of the Earth
THE disasters which have recently befallen the flour- ishing settlements near Vesuvius and in California have once more directed the attention of mankind to the terrific forces which manifest themselves by volcanic eruptions and earthquakes.
The losses of life which have been caused in these two last instances are, however, insignificant by comparison with those which various previous catastrophes of this kind have produced. The most violent volcanic eruption of modern times is no doubt that of August 26 and 27, 1883, by which two-thirds of the island of Krakatoa, 33 square kilometres (13 square miles) in area, situated in the East Indian Archipelago, were blown into the air. Although this island was itself uninhabited, some 40,000 people perished on that occasion, chiefly by the ocean wave which followed the eruption and which caused disastrous inundations in the district. Still more terrible was the destruction wrought by the Calabrian earth- quake of February and March, 1783, which consisted of
1
WORLDS IN THE MAKING
several earthquake waves. The large town of Messina was destroyed on February 5th, and the number of people killed by this event has been estimated at 100,000. The same region, especially Calabria, has, moreover, fre- quently been visited by disastrous earthquakes — again in 1905 and 1907. Another catastrophe upon which history dwells, owing to the loss of life (not less than 90,000), was the destruction of the capital of Portugal on November 1, 1755. Two-thirds of the human lives which this earthquake claimed were destroyed by a wave 5 m. in height rushing in from the sea.
Vesuvius is undoubtedly the best studied of all vol- canoes. During the splendor of Rome this mountain was quite peaceful — known as an extinct volcanic cone so far as history could be traced back. On the extraordinari- ly fertile soil about it had arisen big colonies of such wealth that the district was called Great Greece (Grsecia
Fig. 1. — Vesuvius, as seen from the Island of Nisida, in moderate activity
Magna). Then came, in the year 79 A. D., the devastating eruption which destroyed, among others, the towns of Herculaneum and Pompeii. The volumes of gas, rushing forth with extreme violence from the interior of the earth, pushed aside a large part of the volcanic cone whose remnant is now called Monte Somma, and the falling masses of ashes, mixed with streams of lava,
2
VOLCANIC PHENOMENA AND EARTHQUAKES
built up the new Vesuvius. This mountain has repeat- edly changed its appearance during later eruptions, and was provided with a new cone of ashes in the year 1906. The outbreak of the year 79 was succeeded by new eruptions in the years 203, 472, 512, 685, 993, 1036, 1139, 1500, 1631, and 1660, at quite irregular intervals. Since that time Vesuvius has been in al- most uninterrupted activity, mostly, however, of a harm- less kind, so that only the cloud of smoke over its crater indicated that the internal glow was not yet extinguished. Very violent eruptions took place in the years 1794, 1822, 1872, and 1906.
Other volcanoes behave quite differently from these violent volcanoes, and do hardly any noteworthy dam- age. Among these is the crater-island of Stromboli, situ- ated between Sicily and Calabria. This volcano has been in continuous activity for thousands of years. Its erup- tions succeed one another at intervals ranging from one minute to twenty minutes, and its fire serves the sailors as a natural light-house. The force of this volcano is, of course, unequal at different periods. In the summer of 1906 it is said to have been in unusually violent activity. Very quiet, as a rule, are the eruptions of the great vol- canoes on Hawaii.
Foremost among the substances which are ejected from volcanoes is water vapor. The cloud floating above the crater is, for this reason, the surest criterion of the activity of the volcano. Violent eruptions drive the masses of steam up into the air to heights of 8 km. (5 miles), as the illustrations (Figs. 1 to 4) will show.
The height of the cloud may be judged from the height of Vesuvius, 1300 metres (nearly 4300 ft.) above sea- level. The illustration on page 4 (Fig. 2) is a repro- duction of a drawing by Poulett Scrope, representing the
WORLDS IN THE MAKING
Vesuvius eruption of the year 1822. There seems to have been no wind on this day; the masses of steam formed a cloud of a regular shape which reminds us of a pine-tree. According to the description of Plinius, the cloud noticed at the eruption of Vesuvius in the year 79
Fig. 2. — Eruption of Vesuvius in 1882. (After a contemporaneous drawing by Poulett Scrope)
must nave been of the same kind. When the air is not so calm the cloud assumes a more irregular shape (Fig. 3). Clouds which rise to such elevations as we have spoken of are distinguished by strong electric charges. The
4
VOLCANIC PHENOMENA AND EARTHQUAKES
vivid flashes of lightning which shoot out of the black clouds add to the terror of the awful spectacle.
The rain which pours down from this cloud is often mixed with ashes and is as black as ink. The ashes have a color which varies between light -gray, yellow -gray, brown, and almost black, and they consist of minute spherules of lava ejected by the force of the gases and rapidly congealed by contact with the air. Larger drops of lava harden to volcanic sand — the so-called "lapilli" (that is, little stones), or to "bombs," which are often furrowed by the resistance offered by the air, and turn pear-shaped. These solid products, as a rule, cause the greatest damage due to volcanic eruptions. In the year 1906 the weight of these falling masses (Fig. 4) crushed in the roofs of houses. A layer of ashes 7 m. (23 ft.) in thickness buried Pompeii under a protective crust which had covered it up to days of modern excavations. The fine ashes and the muddy rain clung like a mould of plaster to the dead bodies. The mud hardened after- wards into a kind of cement, and as the decomposition products of the dead bodies were washed away, the moulds have provided us with faithful casts of the ob- jects that had once been embedded in them. When the ashes fall into the sea, a layer of volcanic tuffa is formed in a similar manner, which enshrines the animals of the sea and algse. Of this kind is the soil of the Campagna Felice, near Naples. Larger lumps of solid stones with innumerable bubbles of gases float as pumice-stone on the sea, and are gradually ground down into volcanic sand by the action of the waves. The floating pum- ice-stone has sometimes become dangerous or, at any rate, an obstacle to shipping, through its large masses; that was, at least, the case with the Krakatoa eruption of 1883.
5
WORLDS IN THE MAKING
Among the gases which are ejected in addition to water vapor, carbonic acid should be mentioned in the first instance; also vapors of sulphur and sulphuretted hydrogen, hydrochloric acid, and chloride of ammonium, as well as the chlorides of iron and copper, boric acid, and other substances. A large portion of these bodies is precipitated on the edges of the volcano, owing to
Fig. 3. — Eruption of Vesuvius in 1872. (After a photograph. )
the sudden cooling of the gases. The more volatile con- stituents, such as carbonic acid, sulphuretted hydrogen, and hydrochloric acid, may spread over large areas, and destroy all living beings by their heat and poison. It was these gases, for example, which caused the awful devastation at St. Pierre, where 30,000 human lives were destroyed on May 8, 1902, by the eruption of Mont Pelee. The ejection of hydrogen gas, which, on emerging from
6
VOLCANIC PHENOMENA AND EARTHQUAKES
the lava, is burned to water by the oxygen of the air, has been observed in the crater of Kilauea.
The ashes of the volcanoes are sometimes carried to vast distances by the air currents — e. g., from the west- ern coast of South America to the Antilles; from Iceland to Norway and Sweden; from Vesuvius (1906) to Hoi- stein. Best known in this respect is the eruption of the Krakatoa, which drove the fine ashes up to an ele-- vation of 30 km. (18 miles). The finest particles of these ashes were slowly carried by the winds to all parts of the earth, where they caused, during the following two years, the magnificent sunrises and sunsets which were spoken of as "the red glows." This glow was also observed in Europe after the eruption of Mont Pelee. The dust of Krakatoa further supplied the material for the so-called "luminous clouds of the night/' which were seen in the years 1883 to 1892 floating at an elevation of about 80 km. (50 miles), and hence illuminated by the light of the sun long after sunset.
The crater of Kilauea, on the high volcano of Mauna Loa, in Hawaii — this volcano is about of the same height as Mont Blanc — has excited special interest. The crater forms a large lake of lava having an area of about 12 sq. km. (near- ly 5 sq. miles), which, however, varies considerably with time. The lava boiling at red glow is constantly emitting masses of gas under slight explosions, spurting out fiery fountains to a height of 20 in. (65 ft.) into the air. Here and there lava flows out from crevices in the wall of the crater down the slope of the mountain, until the surface of the lake of lava has descended below these cracks. As a rule, this lava is of a thin fluid consistency, and it spreads, therefore, rather uniformly over large areas. Of a similar kind are also the floods of lava which are sometimes poured over thousands of square kilometres
WORLDS IN THE MAKING
Fig. 4. — Photograph of Vesuvius, 1906. Chiefly clouds of ashes
on Iceland. The so-called Laid eruption of the year 1783 was of a specially grand nature. Though occurring in an uninhabited district, it did a great amount of dam- age. In the more ancient geological periods, especially in the Tertiary age, similar sheets of lava of vast ex- tensions have been spread over England and Scotland (more than 100,000 sq. km., roughly, 40,000 sq. miles); over Deccan, in India, 400,000 sq. kins. (150,000 sq. miles), up to heights of 2000 m. (6500 ft.); and over Wyoming, Yellowstone Park, Nevada, Utah, Oregon, and other districts of the United States, as well as over British Columbia.
In other cases the slowly ejected lava is charged with large volumes of gases, which escape when the lava
8
VOLCANIC PHENOMENA AND EARTHQUAKES
congeals and burst it up into rough, unequal blocks, forming the so-called block lava (Fig. 5). The streams of lava can likewise produce terrible devastation when they descend into inhabited districts; on account of their slow motion, they rarely cause loss of life, however.
Where the volcanic activity gradually lessens or ceases, we can still trace it by the exhalations of gas and the springs of warm water which we find in many districts where, during the Tertiary age, powerful volcanoes were ejecting their streams of lava. To this class belong the famous geysers of Iceland, of Yellowstone Park (Fig. 6), and of New Zealand; also the hot springs of Bo- hemia, so highly valued therapeutically (e. #., the Karls- bad Sprudel); the Fumaroli of Italy, Greece, and other countries, exhaling water vapor; the Mofettse, with their exhalations of carbonic acid (of frequent occurrence in the district of the Eifel and on both sides of the middle Rhine, in the Dogs Grotto near Naples, and in the Valley of Death in Java) ; the Solf atara, exhaling vapors of sul- phur— sulphuretted hydrogen and sulphur dioxide (they are found near Naples on the Phlegrsean Fields and in Greece) ; as well as many of the so-called mud volcanoes, which eject mud, salt water, and gases (as a rule, car- bonic acid and hydrocarbons) — for example, the mud volcanoes near Parma and Modena, in Italy, and those near Kronstadt, in Transylvania.
The extinct volcanoes, of which some, like the Acon- cagua, 6970 m. (22,870 ft.), in South America, and the Kilimanjaro, in Africa, 6010 m. (19,750 ft.), rank among the highest mountains, are exposed to a rapid destruc- tion by the rain, because they consist largely of loose materials — volcanic ashes with interposed layers of lava. Where these lava streams expand gradually, they pro- tect the ground underneath from erosion by water, and
9
WORLDS IN THE MAKING
Fig. 5. — Block lava on Mauna Loa
in this way proper cuts .are formed on the edges of the lava streams, passing through the old volcano and through the sedimentary strata at deeper levels.
The old volcano of Monte Venda, near Padua, affords an interesting example of this type. We can observe there how the sedimentary limestone has been changed by the lava, which was flowing over it, into marble to a depth of about 1 m. (3 ft.) Sometimes the limestone which is lying over the lava has also undergone the same transformation, which would indicate that lava has not only been flowing above the edge of the crater, but has
also forced itself out on the 'sides through the fissures
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crs
•< CO P >
WORLDS IN THE MAKING
between two layers of limestone. Massive subterranean lava streams of this kind are found in the so-called lak- kolithes of Utah and in the Caucasus. There the supe- rior layers have been forced upward by the lava pressing from below; the lava froze, however, before it reached the surface of the earth, where it might have formed a volcano. Quite- a number of granites, the so-called batholithes, chiefly occurring in Norway, Scotland, and Java, are of similar origin. Occasionally it is only the core of congealed lava that has remained of the whole
volcano. These cores, which originally filled the pipe of the crater, are frequent in Scot- land and in North America, where they are designated "necks" (Fig. 7).
The so-called canons of the Colorado Pla- teau, with their almost vertical walls, are the results of the erosive
action of rivers. A drawing by Button shows a wall of this kind more than 800 m. (2600 ft.) in height, through four fissures of which lava streams have forced their way up to the surface (Fig. 8). Over one of these fissures a small cone of volcanic ashes is still visible, while the cones which probably overtopped the three other fissures have been washed away, so that the veins end in small "necks." Evidently a very fluid lava — strong percentages of mag- nesia and of oxide of iron render the lava more fluid than an admixture of silicic acid, and the fluidity is
further increased by the presence of water — has been
12
Fig. 7. — Mato Tepee in Wyoming, U. S. A. Typical volcanic " Neck "
VOLCANIC PHENOMENA AND EARTHQUAKES
forced into the fissures which were already present, and has reached the surface of the earth before it froze. The
t
\
Fig. 8. — Clefts filled with lava and volcanic cone of ashes, Torowheap Canon, Plateau of Colorado. Diagram.
driving force behind them must have been pretty strong; else the lava streams could not have attained the neces- sary velocity of flow.
When the Krakatoa was blown into the air in 1883 half of the volcano remained behind. This half clearly shows the section of the cone of ashes, which has been but very slightly affected by the destructive action of the water. We find there in the central part the light- colored stopper of lava in the volcano pipe, and issuing from it more light-colored beds of lava, between which darker strata of ashes can be seen.
The distribution of volcanoes over the surface of the earth is marked by striking regularities. Almost all the volcanoes are situated near the shores of the sea. A few are found in the interior of East Africa; but they are, at any rate, near the Great Lakes of the equatorial
WORLDS IN THE MAKING
regions. The few volcanoes which are supposed to be situated in Central Asia must be regarded as doubtful. We miss, however, volcanoes on some sea-coasts, as in Australia and along the long coast-lines of the Northern Arctic Ocean to the north of Asia, Europe, and America. Volcanoes occur only where great cracks occur in the crust of the earth along the sea-coast. Where such fis- sures are found, but where the sea or large inland lake basins are not near — as, for instance, in the Austrian Alps — we do not meet with any volcanoes ; such districts are, however, renowned for their earthquakes.
Since ancient ages the belief has been entertained that the molten masses of the interior of the earth find an outlet through the volcanoes.. Attempts have been made to estimate the depth of the hearths of volcanoes, but very different values have been deduced. Thus, the hearth under the volcano of Monte Nuovo, which was thrown up in the year 1538 on the Phlegrsean Fields, near Naples, has been credited with depths varying from 1.3 km. to 60 km. (1 mile to 40 miles) ; for the Krakatoa, estimates of more than 50 km. (30 miles) have been made. All these calculations are rather aimless; for the volcanoes are probably situated on folds of the earth-crust, through which the fluid mass (the magma) rushes forth in wedges from the interior of the earth, and it will presumably be very "difficult to say where the hearth of magma ends and where the volcanic pipe commences. The Kilauea gives the visitor the impression that he is standing over an opening in the crust of the earth, through which the molten mass rushes forth directly from the interior of the earth. (Fig. 9.)
As regards the earth-crust, we know from observations in bore-holes made in different parts of the world that the temperature increases rather rapidly with the depth,
14
VOLCANIC PHENOMENA AND EARTHQUAKES
on an average by about thirty degrees Cent, per kilometre (about 1.6° F. per 100 feet). It must be remarked, how- ever, that the depth of our deepest bore-holes hardly exceeds 2 km. (Paruchowitz, in Silesia, 2003 m., or 6570 ft.; Schladebach, near Merseburg, Prussian Saxony, 1720 m.). If the temperature should go on increasing at the rate of 30 degrees Cent, for each further kilometre, the temperature at a depth of 40 kilometres should attain degrees at which all the common rocks would melt. But the melting-point certainly rises at the same time as the pressure. The importance of this circumstance was,
Fig. 9. — The Kilauea Crater on Hawaii
however, much exaggerated when it was believed that for this reason the interior of the earth might possibly be solid. Tammann has shown by direct experiments that the temperature of fusion only rises up to a certain press-
15
WORLDS IN THE MAKING
ure, and that it begins to decrease again on a further increase of pressure. The depths indicated above are therefore not quite correct. If we assume, however, that other kinds of rock behave like diabase — the melting- point of which, according to the determinations of Barus, rises by 1° Cent, for each 40 atmospheres of pressure corresponding to a depth of 155 m. — we should conclude that the solid crust of the earth could not have a greater thickness than 50 or 60 km. (40 miles). At greater depths we should therefore penetrate into the fused mass. On account of its smaller density the silicic acid will be concentrated in the upper strata of the molten mass, while the basic portions of the magma, which are richer in iron oxide, will collect in the lower strata, owing to their greater density.
This magma we have to picture to ourselves as an ex- tremely viscid liquid resembling asphalt. The experi- ments of Day and Allen show that rods, supported at their ends, of 30 x 2 x 1 mm. of different minerals, like the feldspars microcline and albite, could retain their shape for three hours without curving noticeably, although their temperature was about a hundred degrees above their melting-point, and although they appeared completely fused, or, more correctly, completely vitrified-^wihen taken out of the furnace. These molten silicates behave very differently from other liquids like water and mercury, with which we are more accustomed to deal.
The motion and diffusion in the magma, and especially in the very viscous and sluggish acid portions of the upper strata, will therefore be exceedingly small, and the mag- ma will behave almost like a solid body, like the minerals of the experiments of Day and Allen. The magmas of volcanoes like Etna, Vesuvius, and Pantellaria may, therefore, have quite different compositions, as we should
16
VOLCANIC PHENOMENA AND EARTHQUAKES
conclude from their lavas without our being forced to believe, with Stubel, that these three hearths of vol- canoes are completely separated, though not far removed from one another. In the lava of Vesuvius a tempera- ture of 1000 or 1100 degrees has been found at the lower extremity of the stream. From the occurrence in the lava of certain crystals like leucite and olivin, which we have reason to assume must have been formed before the lava left the crater, it has been concluded that the lava temperature cannot have been higher than 1400 degrees before it left the volcanic pipe.
It would, however, be erroneous to deduce from the temperature of the lava of Vesuvius that the hearth of the volcano must be situated at a depth of approximate- ly 50 kilometres. Most likely its depth is much smaller, perhaps not even 10 kilometres. For there, as every- where where volcanoes occur, the crust of the earth is strongly furrowed/and the magma will just at the spots where we find volcanoes come much nearer to the sur- face of the earth than elsewhere.
The importance of water for the formation of vol- canoes probably lies in the fact that, in the neighbor- hood of cracks under the bottom of the sea, the water penetrates down to considerable depths. When the water reaches a stratum of a temperature of 365 degrees --the so-called critical temperature of water — it can no longer remain in the liquid state. That would not prevent, however, its penetrating still farther into the depths, in spite of its gaseous condition. As soon as the vapor comes in contact with magma, it will eagerly be absorbed by the magma. The reason is that water of a temperature of more than 300 degrees is a stronger acid than silicic acid ; the latter is therefore expelled by it from its compounds, the silicates, which form the main constituents of the
17
WORLDS IN THE MAKING
magma. The higher the temperature, the greater the power of the magma to absorb water. Owing to this absorption the magma swells and becomes at the same time more fluid. The magma is therefore pressed out by the action of a pressure which is analogous to the osmotic pressure by virtue of which water penetrates through a membrane into a solution of sugar or salt. This press- ure may become equivalent to thousands of atmos- pheres, and this very pressure would raise the magma up the volcanic pipe even to a height of 6000 in. (20,000 feet) above the sea-level. As the magma is as- cending in the volcanic pipe it is slowly cooled, and its capacity for binding water diminishes with falling tem- perature. The water will hence escape under violent ebullition, tearing drops and larger lumps of lava with it, which fall down again as ashes or pumice-stone. After the lava has flown out of the crater and is slowly cooling, it continues to give off water, breaking up under the for- mation of block lava (see Fig. 5). If, on the other hand, the lava in the crater of the volcano is comparatively at rest, as in Kilauea, the water will escape more slowly; owing to the long - continued contact of the surface layer of lava with the air, little water will remain in it, the water being, so to say, removed by aeration, and the lava streams will therefore, when congealing, form more smooth surfaces.
In some cases volcanoes have been proved (Stiibel and Branco) not to be in connection with any fractures in the crust of the earth. That holds, for instance, for sev- eral volcanoes of the early Tertiary age in Swabia. We may imagine that the pressure produced by the swelling of the magma became so powerful as to be able to break through the earth-crust at thinner spots, even in the absence of previous fissures.
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VOLCANIC PHENOMENA AND EARTHQUAKES
If, in our consideration, we follow the magma farther into the depths, we shall not find any reason for assum- ing that the temperature will not rise farther towards the interior of the earth. At depths of 300 or 400 km. (250 miles) the temperature must finally attain degrees such that no substance will be able to exist in any other state than the gaseous. Within this layer the interior of the earth must, therefore,