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THE PULSE OF THE EARTH
The Pulse of the Earth BY
J. H . F. UMBGROVE D. SC. (LEYDEN)
HON. F. R. S. E.; HON. MEMB. N . Y. Ac. Sc. MEMB. R. NETHERL. Ac. SC.
PROFESSOR OF GEOLOGY AT DELFT HOLLAND
SECOND EDITION
With 8 partly coloured plaks, 204 textligures and I2 tables
THE HAGUE
MARTINUS NIJHOFF Photomechanicalreprint I97I
© I97I by Martinus Nijhoff, The Hague, Netherlands Softcover reprint of the hardcover 1 at edition I97 I
All rights reserved, including the right to translate 01' to
refrt'oduce this book 01' parts thereof in any form
ISBN 978-94-010-3019-9 ISBN 978-94-010-3017-5 (eBook) DOI 10.1007/978-94-010-3017-5
In memory of A. C. U mbgrove-Gordon my Mother with sincere feelings of gratitude
LIST OF ILLUSTRATIONS
PREFACE ...
CHAPTER I. SPACE AND TIME
CONTENTS
INTRODUCTION • • • • • • . . . . . . . . . . . . . . . . . . . . THE UNIVERSE, THE SOLAR-SYSTEM AND THE EARTH •.. .. .....
Cosmic dimensions. Spiral galaxies. The expanding universe. The origin of the solar-system.
THE BIRTH OF THE MOON . • • . . . . . . . . . . . . The earth and the moon. Lunar volcanism.
THE EARTH'S INTERIOR • . . • • . . . • . . . . • . . . . . . Interpretation of seismic data. Two different theories on the internal constitution of the earth.
THE AGE OF THE EARTH AND THE UNIVERSE • • . . • . •• •••. Geological figures. Astronomical methods and the age of meteorites.
THE HISTORY OF THE EARTH'S CRUST • . . . • • . • • • . • • • • • . Precambrian and later history. Alterations of the earth's as:pect. A geological cycle. Erosion. Sedimentation. Geosynclines. Foldmg. Facies. Unconformity. Magma. Periodicity. Contents of the following chapters.
REFERENCES • . • • . . . . . • . . . . . . . • . • . • . • . . .
CHAPTER II. MOUNTAIN-CHAINS
Pages XIII
XXI
1 2
6
8
12
15
24
INTRODUCTION . . • . • • • • . . . . • • . . • • . • • . • • • . 26 Analysis of the earth's structural history. Mountain-chains of different ages. Epochs of compression. Classification of mountain-belts.
EpOCHS OF COMPRESSION • • • • • • • . • • • . • • • • • • • • •• 29 The enormous extent of Pre-Cambrian areas. The foundering of older zones and a presumed accretion of the continents. Centri:ugal migration. Dynamic centra of tectonic activity. Alternating increase and decrease of compression. A deep-seated cause and world-wide movements. Exceptions. The influence of the basement. Intersecting structures. Absence of centrifugal displacement.
MOUNTAIN-BUILDING • • . • • • • •• • ••••• • ••••• 33 Epochs of compression and elevation. Rejuvenation. The extent of mountains-belts of various ages.
SUBSIDED BLOCKS • • • • • • • • • . • . . • • • • • • • • • • • • 35 Appalachia and Noya Scotica, Llanoria, Cascadia, Scandia, the submerg-ed area west of the Congo-Basin, Melanesia. Periods of foundering.
REFERENCES • • • • • • • • • • . • . • . • . . • • • . • • • . • 39
CHAPTER III. BASINS AND TROUGHS INTRODUCTION • • • • • • • •
Characteristics of basins and troughs. division.
CONTINENTAL BASINS AND TROUGHS Marginal deeps. Intramontane troughs basins. Discordant basins.
Umbgrovt"
43 Nomenclature and systematic
.. . .. . .. .. .. .. ...... 45 and idiogeosynclines.N uclear
VIII CONTENTS
DEEP-SEA BASINS AND TROUGHS • • • . • • . • • • • . • . . • . • Examples in the East-Indies and a comparison with continental types. The abnormal character of the present situation. Periods of rejuvenation of the continental and submarine relief. An open question.
CHRONOLOGICAL REL1I.TIONS TO OTHER PHENOMENA • • • • • • • • • • • Relations to periods of mountain-building and decreasing compression. A deep internal terrestrial process of world-wide activity.
REFERENCES • • • • • •• . • • . • . • . . . . • • . • . . . . . .
CHAPTER IV. CRUST AND SUBSTRATUM INTRODUCTION • • • • • • • • • • • • . . • • . • . . • . . . . .
The composition of the earth's crust and its substratum. Sial and sima. Continental and oceanic sectors. Volcanic and petrographic consequences.
MAGMATIC CLANS . . . . . • . . . . • • . . • . . • . . . . . . . Theory of the origin of igneous rocks belonging to the pacific and mediterranean clans of differentiation from a parental magma-layer of olivine basalt. Other theories.
TECTONIC AND MAGMATIC CYCLES ......•.... • .. • • • . Crustal folding and the root of a mountain-chain. Belts of isostatic anomalies in the East and West Indies. The magmatic phenomena associated with a subsiding and subsequently buckling crust.
A PERIDOTITE-LAYER IN THE SUBSTRATUM . . • • . . • . . . • . . . . The relation of peridotite intrusions to certain epochs of down-buckling of a sialic mountain-root.
ZONAL MIGRATION OF GEOSYNCLINES; CONTINENTS AND OCEAN-FLOORS The pattern of continental shields. The origin of continents and oceanfloors. A primordial, world-wide sialic layer. The origin of an intermediate layer in the earth's crust.
VOLCANISM IN BASINS ..•• • ... . . . . . . . . . . . The occurrence of basic rocks and the absence of acid rocks.
FRAGMENTATION AND GROWTH OF CONTINENTS ........ . Continental rejuvenation. Periodical supply of sialic melts from the substratum.
SUMMARY REFERENCES . . . . . . . . . . . . . . .
CHAPTER V. OSCILLATIONS OF THE SEA-LEVEL INTRODUCTION • . • • . . . . • • • . • • REGIONAL TRANSGRESSIONS AND REGRESSIONS •
The alternation of fresh and salt-water bodies in the Baltic Region . Other examples of local rhythms.
W ORLO-WIDE TRANSGRESSIONS AND REGRESSIONS • . . • • • • The synchronism and hu~e extent of the major trans- and regressions. Possible causes and coincidences with other phenomena. The amount of positive and negative shifts of the sea-level. An important problematical question.
REFERENCES . . . • . • . . . . . • . • . . . . . . . . • . . . .
CHAPTER VI. THE CONTINENTAL MARGIN INTRODUCTION • . • • • . • • . . . . . . . . . • . . . . . .
Problems of the continental shelves and the oceanic coasts of the continents. Classification of continental shelves.
THE SURFACE OF THE SHELF . •••• .••• • •••.•. •• Hypsometric relation between sea-level and shelf-surface. Older theories on the origin of the shelf. The problem of the shelf-edge at the isobath of 200 meters.
THE INFLUENCE OF CHANGING SE!>-LEVEL . • • • • • . . Amount of eus\atic changes. Their possible influence on the grading of the surface of the shelf.
SUBSIDENCE OF THE SHELF-AREA
Pages 54
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64
66
70
76
81
82
84
84
86 87
89 89
92
95
97
100
104
106
CONTENTS IX
Pages Formations on the outer shelf-surface originally deposited in the littoral zone. Deeper surfaces of the shelf.
THE MARGINAL FLEXURE OF THE CONTINENTS .•. • • • • . • • • • • Phenomena showing a widespread rejuvenation of the oceanic borders of the continents. The theory of the marginal flexure.
MARINE TERRACES ••.•••. The most recent movements along the marginal flexure. Possible dating of the different shelf-surfaces.
THE GEOPHYSICAL SIDE OF THE PROBLEM . • . . . • . . • • • • • • • Gravity at the continental margin. The hypothesis of periodical convection currents in the marginal part of the continents. Correlation with other periodical phenomena.
SUBMARINE VALLEYS .•.....•.. . .••.• ...•••• General statement. Classification. Cases to be excluded. The notched shelf-edge. Hypotheses involving a subaerial origin. Hypotheses invol-ving submarine agencies. Gorges extending over the surface of the shelf. Submarine canyons showing a dendritic river-like pattern.
SUMMARY AND CONCLUSIONS. REFERENCES . . . . . • . . . . . . . . . . . . . .
CHAPTER VII. ISLAND-ARCS
INTRODUCTION . . . . . . . . . . . . . . . . . . Geographical distribution. Phenomena associated with island-arcs. Their counterpart on the continents .
THE PROBLEM • • . . . . . . . . . " ..... . • . • . Restrictions. Short outline of problematic questions to be examined.
PHYSIOGRAPHIC FEATURES . . . . . • . • . . • • . • . . • . Genetic classifications. Angle of arc-curvature. The notion of deepreaching thrustplanes. A simple working hypothesis based on physiographic evidence.
EARTHQUAKE ZONES . . . . . . . . . . . . . . . . . . . . . . C I ass i f i cat ion.
Normal-. intermediate-. and deep foci. The M e c han ism.
Distribution of dilatations and compressions. Similarity of the mechanism giving origin to normal tectonic earth shocks and deep-focus earthquakes.
Geographic distribution of deep-focus earthquakes. Exceptional position of the western and southeastern Pacific.
Dee p-r e a chi n g she a r-z 0 n e s . The action of deep-reaching shear-zones and the theory of convection currents.
TERRESTRIAL MAGNETISM . . . . . . . . . . . . . • . . • • • • • • Agreement with the theory of thermal convection currents. Possible relation between districts of deep-focus earthquakes and anomalies of the vertical component of terrestrial magnetism.
VOLCANISM AND PLUTONISM •........•... The and e sit eli n e.
The boundary between sialic and basaltic sea-floor in the Pacific . Pet r 0 g rap h i cpr 0 v inc e s.
Distribution of igneous rocks belonging to the pacific and mediterranean provinces. Their mode of origin.
I g n e 0 u s roc k sin g e ant i c lin a I bel t s. Plutonism and volcanism in the inner arc. Their mutual relations to epochs of compression. Longitudinal faults and rift-valleys. Volcanotectonic depressions. gncolls rocks in geosynclinal tr.oughs. Their relation to epochs of compression.
109
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139 141
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165
x CONTENTS
Pro b I ems t 0 b e sol v e d. Pages
A summing up of eight problematic points regarding the origin and site of plutonic and volcanic phenomena.
DEEP-SEA BASINS AND TROUGHS . • . . . • • • . • . . . . • . • •• 170 Types of troughs associated with island-arcs. Discussion of a theory on their origin.
ISOSTATIC ANOMALIES ...••..•.••••....•.•. .. 172 The b 0 u n dar y 0 f the Pac i fie Bas i n.
Oceanic fields of positive anomalies and the theory of convection currents. Relation to physiographic and seismic phenomena and to the petrographic character of the sea-floor.
Sin g I eAr c s. Gravimetric profiles across the islands Guam and Yap. Geological interpretation.
D 0 ubi eAr c s. Isostatic anomalies in the East- and West Indies. Relations to the topography of the sea-floor. Factors controlling the formation of a single or a double island-arc.
SYNTHESIS • . • . • . . • . . . • . . . . . . . . _ . . . . . . . G e n era 1st ate men t. Sit e 0 f the 0 ute r arc.
Crustal waves due to increasing compression. Crustal down-buckle in the zone of strong seismic activity .
Tim e 0 for i gin and e poe h s of r e j u v e nat ion. Time of origin of the crustal root and epochs of rejuvenation. Origin of a belt of serpentines and other ultrabasic rocks. Respectable antiquity of the zone~
o rig i n 0 f the d 0 u b lea r c. Crustal waves accompanying the zone of strongly negative anomalies. Origin of deep-sea furrows due to isostatic rise of the negative zone. Origin of the double arc. Central depression on the outer arc. The volcanic inner arc and the geosynclinal troughs on their continentward side. Different types of deep-sea basins. Raised reef-limestones.
Dee p-s e a fur row s. Remarkable situation of the island Sumba.. Relation of its site to the belt of negative anomalies and the submarine topography.
The v 0 I can i c i nn era r c. Restriction of volcanism to the concave side of an island festoon. Periodical manifestation of volcanism on the inner arc. Absence of volcanism on the outer arc. Interpretation of Upper Tertiary volcanic rocks on islands of the outer arc and on Sumba. The double row of volcanoes in the northern Moluccas. The distribution of active and extinct volcanoes in the Southern Moluccas.
Bas ins and T r 0 ugh s b e h i n d the inn era r c. Idiogeosynclines. The site of igneous rocks of the mediterranean clan. Deep-sea basins.
Po sit i v e an 0 m a lie s 0 f Iso s t as y. Possible cause of their origin. Relation to the belt of negative anomalies and to periodical epochs of compression in the earth's crust.
The inverted arc of Celebes. Absence of a volcanic "inner" arc. Plutonism and volcanism at the convex side of the negative zone. Tentative interpretation of the major structural features of Celebes.
177
EVOLUTION • • • • • • • • • • • . . . • • . . • . • . • • • • . • 200 The question of evolutionary stages represented by different types of island-arcs. Island-arcs and mountain-belts on the continent.
UNSOLVED PROBLEMS •••••.•••••••.•••.•••.• 205 Absence of island-arcs along the southwestern and eastern borders of the Pacific. Japan and the Philippine archipelago.
SUMMARY REFERENCES
208 214
CONTENTS
CHAPTER VIII. THE FLOOR OF THE OCEANS
XI
Pages
INTRODUCTION . . . . . . . . .. . .' . . . . . . . . . . . . . 217 The antipodal arrangement of ~Qntinental blocl,{.s and oceanic defres-sians. The tetrahedral theory. Different hypotheses on the origin 0 the oceanic receptacles. '
THE MAJOR .CHARACTERISTICS OF THE BOTTOM.-R:e:LIEF ......... 218 A division into four areas and a comparison With geological and geophy-sical data. Antarctic basins. North-Polar basin . .
THE ATLANTIC OCEAN AND THE WESTERN PART OF. THE INDIAN OCEAN 220 CharaCteristics ' of the relief and their geological significance. Symme-trical features. Rejuvenation of the relief. Sunken blocks. Conclusions.
THE PACIFIC OCEAN ...... . . . ... . .....•.... , 227 Characteristics of the relief and their geological significance. Sunken blocks.
THE DISTRIBUTION OF ISOBATHIC AREAS .... . .... 229 The occurrence of three favored levels on the earth's surface.
THE PROBLEM . . . . . . . . . . . . . . . . . . . . . 230 The six main points of the problem.
CONTINENTAL DRIFT . . . . . . . . . . . . . . . . . . . . . . . . 230 Drifting apart of continental blocks. The origin of the floor of the Atlan-tic by stretching of a sialic block. Biological evidence.
SUBMERGED CONTINENTS . . . . . . . . . . . . . . . . . . . . 233 The relation of foundering blocks to the oceanic water-economy. The foundering of a continental block and its thinning.
THE HVPOTHESIS OF PERMANENCE . . . . . . . . . . . . . . . . . . 237 Permanence cum grano salis. Changeable factors. Isthmian links.
TRANS-OCEANIC MOUNTAIN-CHAINS ..... . .. . ........ 239 The abrupt ending of folded belts on either side of the Atlantic. A new theory on their possible connections across the oceanic area.
THE ORIGIN OF CONTINENTS AND OCEANIC RECEPTACLES . . . . . 241 Recapitulation of problematic points. Theories on a primeval earth surface of basalt. The origin of continents and oceans and the resonance theory of the moon. The folding and drifting of a world-encircling sialic layer during early Pre-Cambrian time and the origin of primordial continents and sial-free ocean-floors. A possible process of early Pre-Cambrian stretching of a Sial-layer. The possible influence of primeval convection-currents.
SUMMARY .. ... 251 REFERENCES . . . . . . . . . . . . . . . . . . . 254
CHAPTER IX. IcE-AGES
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . 257 THE PERIODICITY OF CLIMATES . . .. ... ... .. . .. .... 260
Major periodicity of 250 million years. The duration of a glaciation. Visions of the future. Intervening periods of temperate climate. Periods of a minor differentiation of the climate.
THE EARTH'S NORMAL CLIMATE .... . . . .......... . . 261 The uniformity of the landflora. The migration of land animals. Faunistic provinces in the sea. The desert belts.
THE ABNORMAL CHARACTER OF PRESENT CONDITIONS . . . . . . . . . . 266 Climatic zones. The differentiation of the flora and fauna. Present condi-tions and the interpretation of the past.
THE PROBLEM . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 The four aspects of the problem.
THE RELATION BETWEEN PERIODICITY AND PHYSICO-GEOGRAPHICAL FAC-'rORS . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . 267
The major epochs of mountain-building. The amount of carbon-dioxyde
XII CONTENTS
Pages in the atmosphere. The distribution of land and sea. The influence of vol-canic dust. The minor epochs of mountain-building.
THE DEEPER CAUSES OF PERIODICITY • • • • • • • • • • • . • . . . . 269 Correlated phenomena and subcrustal processes. Thermal cycles.
THE RAPID GROWTH AND SUBSEQUENT RETREAT OF AN ICE-CAP • • . • • • 270 The cooling-power of an ice-cap. The retreat of the last Scandinavian ice-cap. The effect of thinning of the ice-sheet and of the elevation of the land. The influence of a lowering of the sea-level.
INTERGLACIAL PERIODS •.•••••••••••••••.•••• 272 The influence of three cosmic variables. Tentative curves of solar radia-tion.
THE GEOGRAPHICAL LOCATION OF AN ICE-CAP •••••..••..•. 274 A theoretical. diagram of the atmospheric circulation. Actual deviations from the scheme. The sites of Pleistocene ice-caps. Isotherms and isoflors .of the Eocene compared to the present site of the continents. Botanical evidence from earlier periods. The Upper Paleozoic glaciation. Objections against the hypothesis of continental drift and the supposed shifting of the poles. Sunken landbridges. A "not impossible" reconstruction of geographic conditions during the Upper Paleozoic glaciation.
THE RESTRICTED INFLUENCE OF COSMIC FACTORS ... The "solar-cyclonic" hypothesis. The rotation of the galactic system
SUMMARY • .. ..... . .. REFERENCES . . • • . . . . . .
CHAPTER X. THE RHYTHM OF LIFE INTRODUCTION .••.••... . . . . . . . . .
The influence of changing environmental factors on the evolution of the fauna.
THE PERIODIC DIFFERENTIATION OF THE FLORA . . . . . . Periodical differentiation of the flora and its coincidence with the major periods of mountain-building and glaciation.
REFERENCES • • • • • • • • . . • . . . . . • . • . . . . • . . .
CHAPTER XI. LINEAR PATTERNS INTRODUCTION ••••••• • .•.•. . . . . . . . . . . • • •
Joints, fractures and other repeatative linear patterns. Lineaments. Morphological features.
PLANETARY SYSTEMS ••••••.•......••••..... Geological and seismologicl!-J evidence. Two bisecting sets of lineaments of world-wide importance: 1'iibe of origin of the planetary lineamentsets. Rejuvenation.
THE PROBLEM ••••••.•••••••.•••••.•••.. Primeval origin of the planetary pattern. Two aspects to be considered (1) The cause of the prevailing directions of the lineament-sets, (2) the repeated rejuvenation of the old plan.
ORIGIN OF THE LINEAMENTS .........•••.....•.. a Ide r The 0 r i e s.
The system Moon-Earth. Other "pre-geological" theories. Contraction. The consolidation of the earth's crust. The influence of anisotropies in the distribution of continents. Meridional lineaments and ocean-floors.
Wan d e r i n g 0 f the Pol e s. Two modes of polar shift. Several geological hypotheses. A recent theory ascribing the origin of the planetary lineament-systems to alarge displacement of the poles in early Pre-C~mbrian times. Reasons to abandon this theory of a polar displacement as well as its predecessors.
PERIODICAl. REJUVENATION • • . • . • • • . • • • • . • . . . . . . D 0 m e-s lia p e del e vat ion san d r i f t-z 0 n e s. The Nor t h Sea Bas i n.
Rejuvenation and periodicity in the North Sea Basin as shown by (1) the
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283 286
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299
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CONTENTS XIII Pages
rate of sedimentation, (2) the paleogeographic development, and (3) the structural history of the basin, especially of its linear structures.
G e n era I con c Ius ion s. SUMMARY . . .. . . . . . 319 REFERENCES . . . . . . . . 319
CHAPTER XII. THE PULSE OF THE EARTH INTRODUCTION .• •. .. .. . . .... .. . . . . . . . . .. 321 CHRONOLOGICAL RELATION OF PERIODIC EVENTS · . . . . . . . . . • . . 321
A concise synopsis and diagrammatic analysis of the periodic phenomena and their respective relations.
A FUNDAMENTAL PROBLEM . . . . . . . . . . . . 324 The problematic nature of the subcrustal processes.
REFERENCES . . . . . . . . . . . . . . . . . . 325
ApPENDIX. DESCRIPTIONS OF PLATES 1-8, AND TABLES I AND II PLATE 1. CALEDONIAN EPOCHS OF COMPRESSION PLATE 2. VARISCIAN EPOCHS OF COMPRESSION PLATE 3. MESOZOIC EPOCHS OF COMPRESSION PLATE 4. CENOZOIC EPOCHS OF COMPRESSION PLATE 5. CHRONOLOGICAL ANALYSIS OF THE CONTINENTS PLATE 6 AND TABLE I. BASINS OF THE SECOND GROUP PLATE 7. DISTRIBUTION OF ROCK CLANS .. .. .. . PLATE 8. GEOLOGY AND GRAVITY FIELD IN THE EAST INDIES TABLE I. SEE UNDER PLATE 6 .. ... .. . . TABLE II. SYNOPSIS OF THE PULSE OF THE EARTH
INDEX . . . .. . . . .. ...... . . . .
LIST OF ILLUSTRATIONS
326 328 332 335 341 342 350 350 350 350 353
If no source is mentioned the illustrations are new or from recent papers by the author.
TEXTFIGURES
Figures. . 1. The dimensions of the planets as compared to the disc of the Sun, and the
Sun as compared to Antares. 2. Our galactic system (after Easton) and the Andromeda nebula.
From W . SHEPERD, De TriomltocAt del' WetenscAtJj> (1941). 3. Diagram of the changes in the form of the Sun during the passage of a star.
Redrawn from H. JEFFREYS, Tile EarlA (1939). 4. Changes in the form of the earth during resonance and the origin of the Moon.
Based on H . JEFFREYS, Tile EarlA (1929). 5. Theophilus - a lunar crater - as compared to the dimensions of some ter
restrial volcanoes. Adaptedfrom B. G. ESCHER (op. cit. 1940).
6. Propagation of seismic waves through the Earth. 7. The internal structure of the earth.
Based on j . B. MACELWANE, PAysics 01 tAe EartA VII (1939) . 8. Two different theories on the constitution of the earth's interior.
Adapted after KUHN and RITTMANN (Geolog. Rundschau 32, 1941 , p . 230, fig. 6).
XIV LIST OF ILLUSTRATIONS
Figures 9. The radioactive series.
From CLARK GOODMAN (Op. cit. 1942, p . 279. fig. 2). 10. Graphic representation of the age of the earth, 11. The town of Le Puy in Southern France. 12. The active Gedeh-Panggerango volcano and the much eroded volcanic ruin
near Plered, Java. 13. The erosive action of the sea, near Camaret. 14. Transgression of Cambrian quartzites on Pre-Cambrian Torridon sandstone. 15. Diagrammatic representation of a geological cycle. 16. Schematic blockdiagram of different facies types.
Based on W. H . TWENHOFEL and R. R. SHROCK, Invertebr~te Paleontology (1935).
17. Glencoul overthrust, north-west Scotland. IS. Old Red resting unconformably on Silurian graywackes. Siccar point,
Scotland. . 19. The Highland boundary fault near Aberfoyle. 20. Geological diagram of Scotland, showing the localities of Fig. 14, 17, IS, 19
and 22. Based on M. GIGNOUX, Geologie Stratigraphique, and on the geological
map of Scotland. . 21. The folded unconformity near Fepin in the ArcJ.ennes. 22. Diagrammatic section across the Pentland Hills near Edinburgh.
After W. H . LAURIE, from J. J. WILLS, The Physiographical Evolution 01 Britain (1929).
23. Structural evolution of Rocky Mountains, SielTa Nevada and Coast Ranges. Adapted from H. STILLE (op. cit. 1936).
24. Cretaceous strata of the Santis-"nappe" which was overthrust on Tertiary "molasse", Northern Swiss Alps.
25. Reconstruction of a Devonian delta of the Appalachian geosyncline. After J . BARRELL, from L. V. PIRSSON and CH. SCHUCHERT, A Textbook
0/ Geology (vol. II) , but slightly modified. 26. Section across the Atlantic coastal plain of North America.
Redrawn after B . L. MILLER (op. cit. 1937). 27. Melanesia and the Pacific Basin.
From H. LADD (op. cit. 1934) . 2S. Schematic review of four types of basins. 29. Diagrammatic block of the marginal trough of the European Variscides.
Based on CH. BARROIS, in M. GIGNOUX, Geologie Stratigraphique, (2d Ed. 1936).
30. Intramontane troughs in the Variscides of Europe. Based on A. BORN and H. STILLE.
31. Intramontane Old Red basins of Great Britain. Redrawn from L. V. PIRSSON and CH. SCHUCHERT, A Textbook 01 Geology.
32. Idiogeosynclines in the western part of the East Indies. 13. Section across the geosynclinal basin of eastern Borneo.
Redrawn after H . JETZLER. Das Olfeld Sanga-Sanga in Koetei (Zeitschr. f. praktische Geologie 1926) .
34. The Ferghana- and Tarim basins and the surrounding mountain-chains. Based on A. BORN and K. LEUCHS.
35. The basin of Paris and its surroundings. Based on "Carte Geologique de la Fra'IICe, I " I,OOO,ooo" .
36. Upper Tertiary anticlines in the island Buton (East Indies). Based on the geological map of Buton by W. HETZEL.
37. Raised reef-terraces of the island Kissar, southern Moluccas. From PlI . H . KUENEN (The Snellius Expedition V, part 2, fig. 70).
3S. Isometric blockdiagram of the submarine relief near the island Bogoslof, Aleutians.
39. Types of submarine basins and troughs in the East Indies. Redrawn from PH. H. KUENEN (Snellius Expedition, vol. V, part 1,
1935) .
LIST OF ILLUSTRATIONS xv Figures
40. Distribution of the abyssal coccolith-ooze in the Caspian basin during Maastrichtian times.
Redrawn from S. VON BUBNOFF, Geologie von Europa (Vol. 1). 41 . Diagram of a continental cross-section.
Based on R. A. DALY, B. GUTENBERG, J. J . MACELWANE and A. RITTMANN.
42. Schematic sections across the earth's c::rust. Based on R. A. DALY (op. cit. 1938).
43 Mineralogical composition of volcanic rocks belonging to different igneous provinces.
After RITTMANN (Vulkane und ihre Tatigkeit p. 91, fig. 195) . 44. Schematic representation of the rising migmatite front in the volcanic inner
arc of the East Indies. From R. W . VAN BEMMELEN (De Ingenieur in Nederl. Indie V, 1938,
p. II, 12, fig. 3). 45. Schematic blOCk-diagram of the Somma-Vesuvius volcano. 46. Schematic representation of the history of the Laziale volcano, S. E. of Rome,
Italy. 47. Symmetrical and asymmetrical types of moutain-roots. 48. Relations between magmatic phenomena and epochs of foldin~.
Redrawn with slight modifications from H. STILLE (op. CIt. 1940) . 49. The relation between tectonic and magmatic cycles. 50. Situation of a world-encircling peridotite layer.
From H. H . HESS (op. cit. 1938, p. 334, fig. 1). 51. Four subsequent tectonic and magmatic cycles in a continental area. 52. The possible origin of an intermediate continental layer. 53. Pleistocene history of the Baltic region.
After SAURAMO. Redrawn from R. A. DALY (op. cit. 1934) . 54. Tertiary transgressions and regressions in the basin of .Paris.
Redrawn from H . STILLE (op. cit. 1924). 55. Transgressions and regressions in the Upper Cretaceous of l!.imburg, in the
Netherlands. Redrawn after UMBGROVE, (Leidsche Geologische Mededeelingen, Vol. I,
1926). 56. Transgressive seas of the Upper Cretaceous.
Composed after VON BUBNOFF, FOURMARIER, GIGNOUX, KOSSMAT and SAPPER.
57. Two curves showing the relative movement of the sea-level in Triassic times. Redrawn from H . STILLE (op. cit. 1924).
58. Profile across the shelf of southern France. After KOSSINA (Handb. der Geophysik, 2, p. 935).
59. Shelf of the North Sea showing drowned rivers debouching near Doggerbank. After C. REID (from DALY, op. cit. 1934, p. 184, fig . 96) .
60. Drowned rivers in~he Java Sea and South China Sea. 61 . Formation of a gradation plane along the coast of St. Helena. 62. Seismic investigation on the continental ·shelf to the west of the English
Channel. From F . C. BULLARD and T . F. GASKELL (op. cit. 1941, fig. 3 and 13) .
63. Probable complications in the formation of the shelf of St. Helena. 64. Distribution of sediments on the continental shelf of the Mid-Atlantic States.
After SHEPARD and COHEE (op. cit. 1936, PI. 4). 65. Deeper surfaces on the outer slopes of the shelf.
(After BOURCART) . 66. Schematic representation of the movements along the continental flexure . 67. Sketch section of Atlantic crustal plain and continental shelf.
From VEATCH and SMITH (op. cit. 1939, p. 34, fig. 11) . 68. Schematic blockdiagram of the Atlantic shelf of the United States from east
of Cape Henry to east of Atlantic City. 69. The continental flexure along the coast of Morocco.
(After BOURCART).
XVI LIST OF ILLUSTRATIONS
Figures 70. Geological section across eastern Australia and the shelf of the Great Barrier
reef. After JENSEN (from J. A. STEERS. The Geogr. Journal 74, 1929, p . 235,
fig. 1) . 71. Gravity observations across the shelf SE of the Canary Islands.
After VENING MEINESZ (op. cit. 1941) . 72. Submarine valleys at the shelf-edge off the coasts of Virginia and Maryland.
From P. R. SMITH (U.S. Coast and Geol. Surv. Bull. 10, 1936). 73. Longitudinal profiles of some canyons ~f the eastern United States.
From VEATCH and SMITH (op. cit. 1939, p. 18, fig. 6). 74. Head of the Congo canyon.
After SHEPARD (Geogr. Rev. 23, 1933). 75. Longitudinal profile of Congo Canyon.
From VEATCH and SMITH (op. cit. 1935, p. 21, fig. 9). 76. Cross-section of Hudson canyon.
From SMITH (op. cit. 1935, p. 20, fig. 8). 77. Dendritic pattern of the Monterey- and Lucia-canyons off the coast of Ca
lifornia . . After SHEPARD (op. cit. 1936) .
78. - Submarine morphology SW of the Missisippi delta. After P. SMITH (op. cit. 1936) .
79. A " graben" type of submarine valley offthe coast of Japan. From F. P. SHEPARD (Journ. of Geol. 1931, p . 347, fig. 3).
8@. The South Norwegian submarine trough showing a deep depression . . From F . P . SHEPARD (op. cit. 1931).
81. Transverse profiles showing the contrast between a submarine valley of the "river" type and a glacial trough.
From F. P . SHEPARD (Journ. of Geology 1931). 82. Three submarine canyons along the notched shelf-edge of Georges Bank.
From H. C. STETSON (Bull. Geol. Soc. of America 47, 1936). 83. Position of the three submarine canyons illustrated by fig. 82:
From H. C. STETSON (op. cit. 1936). 84. Hypothetical stages in the evolution of a submarine canyon.
(From Du TOIT). 85. Kuenen's experiments showing density currents running down the slope of
a shelf-model. After KUENEN (op. cit. 1938).
86. The submarine valley off the Indus delta. From F. P. SHEPARD (op. cit. 1933).
87. Submarine valley of the Hudson. From KUENEN (op. cit. 1938).
88. Submarine canyons of the Tage and Sado, off the Portuguese Coast. (After BOURCART).
89. Nazare canyon. After FREIRE DE ANDRADE (op. cit. 1937).
90. The "gouffre du Cap Breton" off the Atlantic Coast of Southern France. (.\fter BOURCART) .
91. Section of the Montery submarine canyon compared with the Grand Canyon.
After SHEPARD (op. cit. 1936). 92. Island.-festoon in fr.ont of the coast of British Columbia.
(After U.S. chart of the North Pacific basin). 93. Reconstruction of the Alpine geosyncline in the Mesozoic.
From E. ARGAND (Eclogae Geolog. Helvetiae 14, 1916, p. 180). 94. Outcrop, angle and dip of a major thrustplane through the earth's crust .
From P . L. LAKE (Georg. lourn. 78, 1931). 95. Island-arcs of the western Pacific.
After P. L. LAKE (Geogr. Journ. 78, 1931). 96. Diagrammatic section across the Indo-Gangetic synclinorium.
From WADIA (Geology of India, p. 284, fig. 33).
LIST OF ILLUSTRATIONS .>(VII
Figures 97. Direction of initial motion of earthquake shocks originating along a NW-SE
fault in Wurttemberg. . After Miller (from S . W. VISSER, 1937, p. 332, fig. 13).
98. Diagram to illustrate the distribution on the surface of initial compression and dilatation of earthquake shocks deriving from a deeJ?-focus earthquake.
After HONDA (from S. W. VISSER, 1937, p. 333, fig. 14) . 99. Direction of initial motion of shocks deriving from a deep-focus earthquake.
After HqNDA (from S. W. VISSER 54, 1937, p. 334, fig. 15). 100. Epicentres of earthquakes in Hindu-Kush.
From S. W , .VISSER (Gerl. Beitr. zur Geophys. 1936, p. 265, fig. 7). 101. Distribution of intermediate and deep earthquake-foci in the surrounding
of the Pacific. From GUTENBERG and RICHTER (Pllysics 01 tile Earlll 7, 1939).
102. Seismic isobaths in the Japanese area. From S. W. VISSER (Geri. Beitr. zur Geophysik, 1936 p . 257, fig. 1).
103. Epicentres of earthquakes in the Japanese area. From GUTENBERG and RICHTER (Bull Geol. Soc. Am. 1938, p. 275, fig. 3)
104. Volcanic zones of Japan and vicinity. From K. WADATI (The Geophysical Magazine 8, 1935, p. 322, fig. 5) .
105. Seismic activity in the vicinity of. the Aleutian arc. From S. W. VISSER (op. cit. 1936, p. 263, fig. 5).
106. Deep-focus earthquakes along the south-western border of the Pacific Basin. From GUTENBERG and RICHTER (ibidem 1938, p. 279, fig. 6).
107. Seismic isobaths in South America. From S. W. VISSER (op. cit. 1936) .
108. Anomalies of vertical component of terrestrial magnetism. From S. W. VISSER (oJ>. cit. 1937, p. 361).
109. Distribution of rock clans In the East Indies. From H. W. V. WILLEMS.
110. Distribution of active volcanoes in the East Indies. 111. Diagrammatic representation of epochs of plutonism and volcanism in the
Karangkobar region, Java. From R. W. VAN B ...... LEN (De Ing. Ned. Indie 1937, p. IV, fig. 1).
112. Island-arcs bordering the eastern and southeastern coast of Asia. Adapted from LAWSON (Bull. Geolog. Soc. America, vol. 43, 1932, p. 355,
fig. 1). 113. Gravimetric profile across Guam and the Nero deep and Yap and the Yap
deep. After VENING MEINESZ (1934, pI. I).
114. Schematic blockdiagram of an island arc of the Mariana type. 115. Relation between submarine topography and negative anomalies of isostasy
in the East Indies. After VENING MEINESZ (1934, PI. II).
116. Isostatic anomalies in the West and East Indies. From L . M. R. RUTTEN (Tijdschr. Kon. Nederl. Aardr. Genootschap, vol.
LVII, 1940). 117. Distribution of tectonic earthquake foci in the East Indies.
(From S. W. VISSER). 118. Deep-focus earthquakes in the East Indies.
From GUTENBERG and RICHTER (1938, p. 276, fig. 4) . 119. Preliminary representation of the belt of strongly negative anomalies in the
East Indies. (After VENING MEINESZ).
120. Areas of Miocene folding in the East Indies. 121. Review of Tertiary Stratigraphy in the East Indies. 122. Schematic representation of pre-Tertiary history of the East Indies. 123. Five schematic sections showing tentatively the development of a double
island arc. 124. Upper Tertiary depressions on the Kei- and Tanimber Islands. (After FR.
WEBER).
XVIlI LIST OF ILLUSTRATIONS
Figures. 125. Elevated reef limestones and terraces in the southern Moluccas.
Compiled from data appearing in publications by BROUWER, EHRAT, HEERING,DE lONG, KUENEN, MOLENGRAAFF, OYENS, VERBEEK, WANNER and ·ZwIERZYCKY.
126. Schematic representation of different types of marginal deeps. 127. Tentative interpretation of the subcrustal crowding of sima at the concave
side of island-arcs and the origin of plutonism and volcanism in the inner arc. .
128. Distribution of Upper Tertiary volcanic rocks in the southern Moluccas . 129. Active and extinct volcanoes in the southern Moluccas.
(After H. A. BROUWER). 130. Schematic blockdiagram of a double island-arc of the East Indian type. 131. Structural zones ·of .Celebes. 132. Three tentative maps of paleogeographic conditions in the East Indies in
Late Mesozoic, Eocene and Miocene times. 133. Major fault lines of the Pacific relatea to the sites of large . thrust-planes with
deep-focus earthquakes along the Pacific border. From SCHWINNER (Zeitschr. fiir Geophysik, 17, 1941, p. 110, fig. 2).
134. Antipodal distribution of major geographic units. From J. W . GREGORY. (The Geogr. Journ. 13, 1899) .
135. The submarine relief of the Atlantic and Indian Oceans around Antarctica. From H. CLOOS (op. cit. 1937).
136. Basins and ridges on the African continent and in the adjacent deep-sea. From E . KRENKEL, Geologie Atf'ikas (vol. I) .
137. Bathymetric chart of the Atlantic Ocean. Adapted from TH. STOCKS and G. Wiist(pp. cit. 1935) .
138. Symmetry of the northern and southern Atlantic. Redrawn from H. STILLE, op. cit. 1939.
139. BathymetriC chart of the Indian Ocean. From J. H. WISEMAN and R. B. SEYMOUR SEWELL (op. cit. 1937) .
140. The systems of the Carlsberg ridges and the Great Rift-Valley. From J. D . WISEMAN and R. B. SEYMOUR SEWELL (op. cit. 1937) .
141. The earthquake belts of the Indian Ocean and its surroundings. After HECK, from J. D. H. WISEMAN and R. B. SEYMOUR SEWELL (op.
cit. 1937) . 142. Linear arrangement of island groups in the Pacific.
From L . J. CHUBB (op. cit. 1934) . 143. Distribution of the genus Cornus.
From CH. LONGWELL (op. cit. 1945). 144. A comparison . between the geological structures of Scotland and those of
northern Spitsbergen. Partly redrawn after ~OLTEDAHL, from H . FREBOLD. Geologie von Spits
.bef'gen. 145. Transoceanic continents in the Lower Cretaceous.
Redrawn from E. HAUG, Tf'aite de Geologie. 146. The total amount of oceanic waters in geological time.
From PH. H. KUENEN (op. cit. 1937) . 147. Schematic diagram illustrating the hypotheses of a relatively stable and of a
rising floor of the Pacific Ocean. 148. The distribution of Primates according to the hypothesis of permanence.
From W. D . MATTHEW, Climate and Evolution (1915) . 149. A transatlantic isthmian link.
From B . WILLIS (op. cit. 1932). 150. A hypothetical reconstruction of non-transatlantic mountain-chains.
From H . STILLE (op. cit. 1934). 151 . Schematic representation of the origin of sialic continents on a primeval
earth-surface of alkali-basalt, according to the hypothesis of Rittmann. 152. Internal constitution of the Moon and the Earth.
From MOHOROVI(:IC (From Handb. d. Geoph. 3, 1925, p. 476, fig . 171)
LIST OF ILLUSTRATIONS XIX
FIGURES 153. The hypothetical formation. of a primordial continent a.nd a sial-free ocean
floor. 154. Schematic representation of the origin of continents and oceanic receptacles
in the early Pre-Cambrian by a process of buckling and drifting of an originally sialic layer enveloping the whole earth.
155. Distribution of primeval convection-currents in the surface layers of the earth.
From VENING MEINESZ (Versl. Nederl. Akad. Wetensch. 53, 1944, p. 157) . 156. Schematic representation of three groups of hypotheses on the formation
of continents and ocean floors. 157. Ice-sheets and glaciers of the present time. 158. Ice-sheets and glaciers during maximum glaciation in the Pleistocene.
Mainly after ANTEVS and OBRUTCHEW. 159. Upper Paleozoic tillites.
Based on COLEMAN, DAVID, Du To IT, GERTH, etc. 160. Pre-Cambrian tillites.
Based on A. P. COLEMAN (op cit. 1926) . 161. Mesozoic and Eocene tillites.
Based on A. P. COLEMAN (op. cit. 1926) . 162. Lower Paleozoic tillites.
Based on A. P. COLEMAN (op. cit. 1926). 163. Routes of migration of the giant Dinosaurs.
From H. F. OSBORN (op. cit. 1930). 164. The distribution of Upper Cretaceous Rudists.
Adapted from E. DAQUE. Grundlagenund Methodendet' Palaeogeogt'aphie. 165. Desert deposits of Mesozoic times and desert belts of the present time.
Re irawnandadaptejaiterC. E. BROOKS (op. cit. 1926). 166. Cooling power of an ice-cap.
From C. E . P. BROOKS (op. cit . 1926) . 167. Retreat of Fennoscandian ice-cap since the beginning of " post-glacial" times .
Redrawn from R. A. DALY (op. cit. 1934). 168. Graph of the retreat of the Fennoscandian ice-cap. 169. Diagram of atmospheric circulation.
Adapted from W . H. HOBBS (op. cit. 1926). 170 and 171. Changes of mean temperature and mean pressure with increase of
the relative sunspot number to 200. Redrawn from C. E. P . BROOKS (op. cit. 1926) .
172. Eocene "isoflors" in the Northern Hemisphere. From R. W . CHANEY (op. cit. 1940) .
173. The distribution of modern vegetation and January isotherms in the Northern Hemisphere.
From R. W. CHANEY (op. cit. 1940) . 174. Geographic conditions during the Upper Paleozoic ice-ages.
Based on CH. SCHUCHERT, B. WILLIS and C. E . P. BROOKS. 175 and 176. Two possible explanations of glaciation and ice-ages . 177. The cosmopolitan flora of the Lower Carboniferous.
Redrawn from A. C. SEWARD (op. cit. 1931). 178. Upper Paleozoic flora types.
Redrawn from A. C. SEWARD (op. cit. 1931) with added data from publications by W. J .JONGMANS on the flora of Asia and the East Indies.
179. Lineaments as a repeatative pattern in a drainage network in northern France.
After DAUBREE, from Hobbs 1911, fig. 31, Op. 15. 180. Pattern of rivers in the area about Rockland, Michigan.
From HOBBS 1911 , fig. 24, p. 149. 181. Drainage map of a part of the district Nipissing.
From HOBBS, 1911, fig. 25, p. 150. 182. Schematic block diagram of the Guinea-line of volcanoes continuing from
the African continent into the Atlantic.
xx LIST OF ILLUSTRATIONS
Figures 183. Seismo-tectonic lineaments in the surroundings of the Mediterranean.
After SIEBERG (from SONDER, p. 204, fig. 3). 184. The oblique course of the main geographical lines.
After Prinz (from J. W . GREGORY, op. cit. 1899). 185. Schematic representation of a column of sial floating in a simatic substratum. 186. Schematic representation of continental and oceanic columns of sial, (A)
according to the usual conception ; (B) according to the assumption of Milankovitch.
187. Shearing-net based on the assumption of a displacement of the North Pole from near Calcutta over 70° along the meridian of 90° E .L.
From VENING MEINESZ (op. cit. 1943). 188. To the left principal directions of the four lineament-groups of N. W . Europe
shown in fig. 194. 189. Dome-shaped elevation, with rift-valleys and volcanism .
Partly redrawn from H. CLOOS (op. cit. 1937) . 190. A dome-shaped elevation with faults, graben and volcanism.
From H. CLOOS (op. cit. 1937). 191. The formation of rifts according to the theories of Taber.
From S. TABER (Journ. of Geology, 35, 1927). 192. Paleogeographic reconstruction of the Rhine Shield in Mesozoic times.
From CLOOS (after VON BUBNOFF). 193. Paleogeographic reconstruction of the Plateau Central , France, during
Mesozoic times. From CLOOS (after VON BUBNOFF).
194. The North Sea Basin and its surroundings. 195-198. Paleogeographic maps of the Netherlands for Lower, Mid, and Upper
Pliocene, showing a gradual retreat of the coastline. (After P. TESCH).
199- 200. Paleogeographic maps of the Netherlands for Gunz-glacial times and the Gunz-Mindel interglacial.
(After P. TESCH). 201. Schematic block-diagram of crossing river-terraces caused by a tilting
movement. (From K. OESTREICH).
202. Graphs showing the chronological relation of the various periodic phenomena. 203. The "Westralian geosyncline" of Teichert and its supposed connection with
the Banda geosyncline in the East Indies. From C. TEICHERT (op. cit. 1940, p. 107, fig. 1) .
204. Determinations of geological ages.
Plate Plate Plate Plate Plate Plate Plate Plate Table Table
PLATES AND TABLES AT THE END OF THE BOOK
1. Caledonian epochs of compression. 2. Variscian epochs of compression. 3. Mesozoic epochs of compression. 4. Cenozoic epochs of compression. 5. Chronological analysis of the continents . 6. Basins of the second group. 7. Distribution of rock clans. 8. Geology and gravity field in the Netherlands East Indies. 1. Review of basins and troughs.
II. Diagrammatic synopsis of "the pulse of the earth".
PREFACE
Problems of current interest relating to the earth's physical history will be discussed in this volume.
Each chapter constitutes a subject in itself, but the sequence I have chosen will, I hope, show and explain the deeper correlation of several terrestrial processes which, at first sight, appear to be heterogeneous.
The geologist follows the changing face of the earth, the oscillations of the sea-level, the pulsation of folding and mountain-building, the periodicity of the ice-ages, the rhythmical cadence of Life. Just as the physician will draw his conclttsions from outward symptoms when examining his patient, so the geologist tries to discover the deeper significance of the sequence of observed phenomena by ieeling the pulse of the earth.
The many additions and revisions which have had to be made in this second. edition include three new chapters, several new sections in other chapters, I09 new textfigures, I2 tables and 2 plates.
A leu) fundamental geological terms have been explained in Chapter I . Geologists and older students will, I trust, forgive me for handling facts that no longer represent terra incognita to them, realizing that younger undergraduates, biologists and other readers will welcome a concise synopsis concerning matters which, in the following chapters, are presupposed to be generally known. On the other hand the Appendix, consisting of a somewhat dry and monotonous compilatIOn and disCttss,:on of data, is only intended for geologists who desire to examine further the fundamental points laid down in plates I-8 and Chapters II and III.
Most (1/ tlte topics are adapted from lectures delivered in Cambridge, Delft, The Haf!,lIt~ and Lt'vden in the course of the yearsI939-I945.
h 7f1()lIld ncccssilalt· 100 long a list if I were to mention all the names of those 7I(J/tO, in tJ1W way or tuzother. have generously given assistance or contributed in/ormation, 10 all o/wl/om I hereby wish to express my gratitude.,I owe special Ihanks to IItV colleagues and friends Prof. Arthur Holmes of Edinburgh, Dr. E. C. Nul/artl, ami Dr. Harold Jetfreys of Cambridge, Prof. B. G. Escher, I'ro/' H . .f. I_allll11lt! Prof. ]. H. Oort of Leyden, Prof. Ph. H. Kuenen of GrolIinf!,t'll, /Jro/. F .. '1. Vening Meinesz and the late Prof. J. A. A. Mekel of Delft /or their illuminatillg ciisCltssions or critical reading of parts of the manuscl'ipt.
Mr . ./. A. 11a1l Houlen, B. A. , translated the Dutch manuscl'ipt of the first edition into English 1e1illt great devotion and patient pel'severance. I gl'eatly regret that Itt' could 1101 IIlldcrtake tlte translation of the new chapters. I had to il'trite them in English I/lI tsdj, hilt / am 11ery glad to say that some of my friends
XXII PREFACE
in England made linguistic corrections in the manuscript, while Professor Holmes even kindly undertook the onerous task of reading the page proofs. Of course, I remain personally responsible for any mistakes or misprintings that may finally have been overlooked.
I may also mention my ~ndebtedness to Mr. C. van Werkhoven, who executed plates I-8 with such admirable skill and overcame numerous difficulties with great ability. It was he too who put the finishing touches to several figures in the text. Most of the latter, however, lowe to Dr. R. de Wit and Mr. G. A. de Neve, for whose valuable assistance I express my sincere appreciation.
And last but not least, I wish to extend my thanks to Mr. W. Nijhoff, who has published this book with the meticulous care which so unfailingly characterizes his work.
Wassenaar, May I2th I946.
FOREWORD TO THE PHOTOMECHANICAL REPRINT
At the time 01 his death the author was preparing a new edition of this book, as in his opinion it needed a revision.
Several outstanding colleagues, some of them close friends of the author, were asked to try and complete the manuscript for this third edition. But out of respect for the personal touch which gives "The Pulse of the Earth" such a special character, all concerned came to the conclusion that it would prove to be impossible to find a suitable editor.
Because there is a continuing demand lor copies of the second edition Mrs. U mbgrove consented to a completely identical photomechanical reprint.
The Publisher