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Show CALKED TECTONIC MAP OF UTAH AND ADJACENT AREAS ... faujt lines of Utah and surrounding t0 Note the characteristic polygon shape. LT VALLEY PATTERNS R (TENSION) j ,,0F A rift valley showing the erosion cutting along shaped fractures at 120 degree angles. leory On Earth's Crust RANDALL LARSON i Wle Staff Writer i tolly new explanation for mi the earth's crust has inced by Dr. Francis Jristiansen of the Uni-ijepartmeirt Uni-ijepartmeirt of geology. Wstlansen Is known in SU for recently publish- oilher theory propound-; propound-; mvectlons currents as a I i in shaping the earth's ants. sijti his new theory is : lily concerned with fail-, fail-, :the earth's crust, it applies 1 J to fracture characterist-"infinite characterist-"infinite or spherical . u todies." HUE in the earth's crust ! 'store lines called faults. ', : movement occurs along it the result is an earth- t ; J ausly, failures in the i- i mist have been explain- I 'the linear theory, which i ses such fractures to opp- II tees. 'THIS theory does not & for the characteristic ii pattern found in fracture the earth is shrinking or expanding. expand-ing. There are some indications that it may be expanding. This is an alternate theory to the classical idea that the earth is shrinking as it "cools," much like a drying apple. BUT WHETHER the forces were tensional or compressional, the resulting fracture patterns would be much the same, 'Dr. Christiansen reports. Tension forces would be set up in an expanding ex-panding body, and compression forces would be set up in a shrinking one. Of course, both forces could be set up in different diff-erent areas of the same tabular body. This is likely to be the case in the earth's crust. Failures, Dr. Christiansen explains, ex-plains, originate at isolated points in the tabular body. These points are thought to be points of weakness. From these points radiate fracture lines which form "bi-radial or tri-radial sectors." sec-tors." These fractures always form at angles of 120 degrees, and may intersect with sectors from other points as they con- J tinue to '"grow" outward. :i This pattern is seen to Aantage in the Ural 1 'As of Russia, in the Mid- !S :( Ridge and in other out- 1 ''(geologic features. If the i 'Jieory were correct, such 8 belts would tend to i ijht or parallel rather li ' the zigzag patterns : wist in nature. iunt for this irregular ti 3! formation, tt has been ?i that these polygonal Hi 'Wtems are due to ten-si ten-si fs which would explain ill -rgonal pattern character- ' mudcracks and the colli' col-li' the famous Devil's H '"Wyoming. ,;. 'ER current theory is j,. tion currents caused t in dearth's mant- )? " forces which are ;t deformation of the ;"e mantle is the central : ,ot sphere lying be- core and the outer i ;r.,i!!1Ve?ion currnts do 2 e sterns they 3 in the crust '4rflentlally identical to :: Pattern. i :t? wh,ch r- ; C'0" compos- !' :7"iA could be set . Z b l4r body such as ( 'crust, tttsar uncertain at hme to wtiethe |