Apeil 16, 1909] 



SCIENCE 



625 



India. The Malay arc, lapping around the eastern 

 ■end of the Himalaya and swinging far to the 

 south — even beyond the equator — met no such 

 obstacle. It spent itself more freely and formed 

 the most remarkable of the great earth-lobes of 

 Asia,. 



3. At its eastern end the tectonic line of the 

 Aleutian island arc penetrates to the heart of the 

 mountain knot of Alaska, so that westward from 

 about the 148th meridian, west longitude, Alaska 

 belongs structurally to Asia. 



4. The Tuscarora deep, close in front of the 

 Japan and Kurile Island arcs, and also the long, 

 narrow deep, close in front of the Aleutian arc, 

 mark areas probably in part elastically depressed 

 by the weight of the adjacent more or less over- 

 thrust masses. They mark the negative side of 

 these great tectonic lines, while the high, though 

 largely submerged, mountain ranges of the adja- 

 cent island arcs mark the positive, uplifted side 

 of the same lines. These troughs are now unfilled, 

 because the uplifted ranges near them have re- 

 mained largely submerged and hence have sup- 

 plied little or no sediment. 



5. The mountain knot of Alaska was raised to 

 ita extraordinary height by a convergence of 

 crustal creeping movements. It is precisely in the 

 angle where the southeastward creep of the Aleu- 

 tian earth-lobe came into conflict with the south- 

 westward creep of northern North America. 



6. The peculiar rift valleys on the northern and 

 western sides of Greenland suggest a rending and 

 tearing away of Grant Land, Baffin Land and 

 Labrador from Greenland, due apparently to 

 crustal creep towards the south and southwest, 

 Greenland remaining as the great northern horst. 

 The import of these several facts added together 

 is Tertiary southward crustal creep, with periph- 

 eral faulting, folding and uplifting for all the 

 northern continents. 



7. Australia's Tertiary peripheral mountain belt 

 lies in island chains seaward from its northern 

 and eastern coasts, indicating northward and east- 

 ward crustal creep. South America's belt is on its 

 northern and western sides, indicating northward 

 and westward creep. Thus, the two southern con- 

 tinents show in general northward creep, but with 

 a considerable amount of deflection. 



8. The Celebes and Malmahera islands show re- 

 markable " chiragratic " mountain plans, and they 

 are precisely in the zone of conflict between the 

 southward crustal creep of Asia and the north- 

 ward crustal creep of Australia. Borneo is in the 

 same zone and has a similar mountain plan. 



Conclusions. — ^The foregoing facts show crustal 



creep in both hemispheres from high towards low 

 latitudes. This is not explicable by any form of 

 contraction hypothesis, but is the normal result 

 of a force tending to deform the lithosphere by 

 slightly and permanently increasing its oblateness 

 — the same in effect as if the earth's axial rota- 

 tion had been slightly and permanently increased. 

 No contraction hypothesis can account for the oc- 

 currence of this remarkable epoch of mountain 

 making at so recent a time as the Tertiary age, 

 unless it can provide some method of storage of 

 mountain making forces which shall endure and 

 continue to accumulate through several geologic 

 ages, with occasional mountain making in mod- 

 erate degree going on at the same time. 



The action of such a force would cause a de- 

 pression of both polar areas, resulting in crustal 

 creep towards lower latitudes. Inevitably, one 

 polar area would yield before tne other or else in 

 greater amount. The pole from which the first 

 large shift of mass took place \/0uld ever after 

 take the lead and be the more active area in 

 crustal movement, for that first movement would 

 slightly displace the earth's center of gravity, 

 moving it towards the other pole, where the shift 

 of mass was less, and this change itself would 

 intensify the deforming forces at the first pole and 

 diminish them at the other. Thus, the first pole, 

 corresponding to the north pole of the earth, 

 would progressively emerge from the sea, would 

 suffer the greater deformation and would there- 

 fore have an excess of land or continental areas 

 around it, while the other (south) pole would be 

 progressively submerged, would suffer less defor- 

 mation and would have a minimum of land or 

 continental areas around it. This may explain 

 why the north pole is girdled by land and the 

 south pole by water. 



The forces causing southward crustal creep in 

 the northern hemispnere were strongest in high 

 northern latitudes and diminished towards the 

 south; and further, the area of earth-crust upon 

 which the forces acted increased towards the south. 

 I'erhaps these two conditions, modified by the 

 tendency to a limited number of meridional rifts 

 due to girth expansion in the equatorial belt, 

 explain the triangular shape of the continents — 

 broad at the north, where a land belt almost 

 girdles the earth, and tapering in sharp points 

 towards the south. 



Mr. Taylor's paper was discussed by Professors 

 H. F. Eeid, B. K. Emerson, J. Barrell, W. H. 

 Hobbs, A. P. Coleman and F. B. Taylor. 



The session then adjourned at 12:30 p.m. 



The society convened again in two sections at 



