DIVISION XXX GEOLOGY, METEOROLOGY AND GEOGRAPHY DYNAMICAL AND STRUCTURAL GEOLOGY BY KIRTLEY F. MATHER of the earth-blocks separated by the San Andreas fault. The relation of earth temperature Earth Structure.-A critical analysis of the geological relations of earth-condensation and resulting acceleration in rotation of the earth, to buried hills and anticlinal folds, prepared by the late Joseph Barrell as presented by W. T. Thom, Jr. (Am. Journ. Sci., 5th ser., Vol. 10, (Econ. Geol., Vol. 20, pp. 524-530) pp. 408-432, 499-529) indicates that suggested a new application of geolstresses in the earth's body due to ogy to practical affairs as well as an changes of oblateness are wholly sub- interesting train of purely scientific merged beneath those due to change inquiry. The abnormally high temof volume. R. A. Daly (Proc. Am. perature gradients beneath the Salt Phil. Soc., Vol. 64, pp. 283-307) em- Creek and other oil-bearing domes is phasized the close relationship be- attributed to the truncation of the tween mountain building and igneous folds by erosion so that relatively action to a degree not possible before hot strata are now exposed near their the hypothesis of continental dis- tops. Sidney Powers also directed placement had been imagined by Tay- attention to the fertile field for relor and Wegener. Daly describes the search in structural geology, enriched continents as sliding on a thick shell by data pertaining to activities of of hot, basaltic glass, rigid but weak, the petroleum industry in the Midand explains the mountain chains as Continent region (Bull. Geol. Soc. structures compressed on the down-Am., Vol. 36, pp. 379-392). stream sides of gigantic landslides. Geologic Processes.-The causes A factor not ordinarily considered of deposition of calcareous materials by geologists is called to their atten- in sea water have long been of great tion by Warren J. Mead in "The interest. In a critical and experiGeologic Rôle of Dilatancy" (Journ. mental study of Drew's bacterial hyGeol., Vol. 33, pp. 685-698). Dilat-pothesis of lime precipitation, Charles ancy is the expansion of granular B. Lipman (Carnegie Inst. Pub., No. masses when deformed due to the rearrangement of the grains, and the term is expanded to include all volume increase due to deformation. Its consequences have far-reaching geologic significance. It is quite likely, for example, that the active thrustfaults in San Benito County, Cal., described by Paul F. Kerr and Hubert G. Schenck (Bull. Geol. Soc. A great flood of glacier-born waAmerica, Vol. 36, pp. 465-494) are de- ters, which during the ice age swept veloped in response to dilatancy in- down the Snake and Columbia valvolved in the differential movement | leys and resulted in noteworthy ero 340, pp. 181-191) found no proof that deposition of lime is accomplished by bacteria under natural conditions. There are several interactions, physical, organic and atmospheric, constantly going on in the sea-water which determine large lime precipitation without introducing hypotheses such as Drew's. sion as well as deposition of gravel bars and the Portland delta, was described by J. Harlen Bretz (Journ. Geol., Vol. 33, pp. 97-115, 236-259). The close relationship between seismology and structural geology is illustrated by the study of clastic dikes in eastern Washington, made by Olaf P. Jenkins (Am. Journ. Sci., 5th ser., Vol. 10, pp. 234-246), who "is inclined to believe" that the jagged, ramifying sand and dust dikes near Walla Walla are fillings of cracks resulting from earthquakes during or subsequent to the glacial period. Similarly, a study of the earth movements accompanying the Katmai eruption of 1912, made by Clarence N. Fenner (Journ. Geol., Vol. 33, pp. 116-139, 193-223), indicates that the tectonic movements accompanying the eruption were not caused by the surficial faulting in the Valley of Ten Thousand Smokes, which he attributes to the intrusion of a sill-like body of not great thickness beneath its floor. Isostacy.-F. A. Melton presented (Am. Journ. Sci., 5th ser., Vol. 10, pp. 166-174) an interpretation of isostatic anomalies, which emphasizes anew the considerable strength of the earth's crust and suggests the possibility of deep-seated rather than merely surficial heterogeneity within the body of the earth. Eastern Canada.-Discussion concerning the oldest known rocks of North America was rife at the annual meeting of the Geological Society of America, held at Ithaca during the last week of 1924. F. F. Grout (Bull. Geol. Soc. Am., Vol. 36, pp. 351-364) presented data tending to show that the Coutchiching series in the Rainy Lake district was younger than the Keewatin series rather than older as A. C. Lawson had concluded several years ago. Later, George W. Bain described a thick mass of sediments in the Upper Harricana Basin, Quebec, which seem to be distinctly older than the Keewatin rocks. If so, these sediments of the "Okikeska series" are the oldest rocks now known on this continent. Mississippi Valley. Two of the great batholiths of Minnesota, the Vermilion and Giants Range granite masses, are described by Frank F. Grout and Ira S. Allison (Journ. Geol., Vol. 33, pp. 467-508). In each, the differentiation of magmas produced a considerable variety of rocks. The latest addition to the Geologic Atlas of the United States, under preparation by the U. S. Geological Survey, is Folio 219, descriptive of the Central Black Hills in South Da kota, by N. H. Darton and Sidney Paige. As customary in this excellent and valuable series, the geog raphy, geology and mineral resoures of the region are described in detail. Of general interest is the conclusion that the shapes of the Tertiary igneous masses have been greatly influenced by the structure of the rocks invaded by the Tertiary magmas. Coastal Plain.-The contribution which the oil industry is making to detailed knowledge of geologic structure, especially in such areas as the Gulf Coastal Plain where the deter mination of structure solely from rock outcrops is extremely difficult if not impossible, is illustrated by a comparative study of well logs on the Mexia type of structure, made by Frederick H. Lahee (Trans. Am. Inst. Min. and Metall. Engineers, Vol. 71, pp. 1329-1350). The Mexia fault zone is 30 to 40 miles east of the Balcones fault zone, and the two bound a great graben which is broken by numerous minor faults and which extends for many miles across Limestone and Navarro counties, Texas. Cordilleran Region. Among the outposts of the Northern Rocky Mountains on the Great Plains in Central Montana are two small laccolithic masses, North and South Moc casin Mountains. The South Moccasin laccolith is described by Harold S. Palmer (Am. Journ. Sci., 5th ser.. Vol. 10, pp. 119-133). The Bearpaw Mountains, 60 miles farther north, are surrounded by a belt of faulted folds of rather unusual characteristics. Frank Reeves (Am. Journ. Sci., 5th ser., Vol. 10, pp. 187-200) presents evidence that this folding and faulting is quite shallow; al though the formations underlying the Upper Cretaceous strata were involved in the thrust, according to his interpretation, they responded with out being folded or faulted in any manner that has found expression in the structure of the outcropping beds. Describing the Wasatch Mountains, Hyrum Schneider (Journ. Geol., Vol. 33, pp. 28-48) interprets the Wasatch Front as an initial fault-scarp modified by erosion, rather than a faultline scarp, and affirms that some of the ranges in the northeastern part of the Great Basin are fault-blocks. In similar vein, George D. Louderback (Bull. Dept. Geol. Sci., Univ. Calif., Vol. 15, pp. 1-44) concluded that the period of scarp production in the Great Basin, especially in the western portion near the Sierra Nevada, occurred during latest Tertiary or early Quarternary time. W. M. Davis has also considered the Basin Range problem (Proc. Nat. Acad. Sci., Vol. 11, pp. 387-392) and corroborates these results. Pacific Coast.-Richard N. Nelson described the geology of the hydrographic basin of the upper Santa Ynez River, Cal. (Bull. Dept. Geol. Sci., Univ. Cal., Vol. 15, pp. 327396). The region is in the Santa Ynez and San Rafael Mountains, and the report is an excellent study of an area, somewhat difficult of access, rugged, and of complicated geologic structure. The "structural dynamics of the Livermore region" is the title of a paper by Frederick P. Vickery (Journ. Geol., Vol. 33, pp. 608-628) in which a portion of the California Coast Range, 40 miles southeast of San Francisco, is described. 6 miles in diameter, from which between 8 and 15 cubic miles of rock and lava is believed to have been exploded into the air. It is the largest known explosion crater in the world and the nearest counterpart to the craters of the moon. The annual volume descriptive of the mineral resources of Alaska (U. S. Geol. Survey Bull. No. 773) includes papers which discuss the geologic structure of various parts of that territory, written by J. B. Mertie, Jr., W. R. Smith and Kirtley F. Mather. Naval Petroleum Reserve No. 4 occupies a vast and little known portion of the Arctic shore in the vicinity of Point Barrow. The third expedition of geologists of the U. S. Geol. Survey, dispatched to that area, spent the summer of 1925 there, and the report of the first expedition, led by Sidney Paige in 1923, was printed during the year (U. S. Geol. Survey Bull. 772). The low flat coastal plain is now known to be underlain by coal seams and to contain several seepages of oil, but its real value as a petroleum reserve seems still in doubt. SELECT REFERENCES Among the principal books of the year are the following: DAKE, C. L., and BROWN, J. S.-Interpretation of Topographic and Geologic Maps. N. Y., McGraw Hill. D. W.-New EnglandAcadian Shoreline. N. Y., John Wiley and Sons. Alaska.--Aniakchak Crater, discovered in 1922 on the Alaska Peninsula, 150 miles southwest of Mt. Katmai, QUIRKE, T. T.-Elements of Geology. was described by Walter R. Smith N. Y., Holt. (U. S. Geol. Survey Prof. Paper SHIMER, H. W.-An Introduction to 132-J) as a gigantic hole, averaging Earth History. Boston, Ginn & Co. EARTHQUAKES AND VOLCANOES BY KIRTLEY F. MATHER PROFESSOR AT HARVARD UNIVERSITY Perspective. During 1925 a greater time in several years earth tremors number of persons in the United shook the congested districts of the States were startled by earthquakes Eastern States, occasioning a marked than during any previous year in the though probably temporary increase history of this country. For the first of the average man's interest in seismic phenomena. Disasters from earthquakes occurred at Santa Barbara, Cal., Talifu, China, and Osaka, Japan, but in the perspective of history the year was not especially unusual. NEW ENGLAND-MARITIME Eastern Massachusetts was slightly shaken by an earthquake at 8:07 a.m., January 7, which originated not far off Cape Ann. China and bric-abrac were hurled to the floors in towns north of Boston, and the quake was felt as far south as Providence, Rhode Island. were due to the location of the points of origin, beneath an uninhabited wilderness rather than beneath a popu lous city. a Aftershocks.-The tremors of the February 28 quake were numerous and continued over a period of many weeks. In the first week more than hundred tremors were noted in Pointe-au-Pic; on March 3 and 21, temblors were widespread in the St. Lawrence Valley. A shock was felt at Kamouraska and Murray Bay on April 10 and another near the Saguenay River on April 25. The Murray Bay district was again shaken during the night of May 29; none of these tremors did any damage. Eastern Massachusetts.-This section experienced a slight quake at 2:58 a. m. on April 24, which was felt throughout the area surrounding New Bedford, Marion, Middleboro and Brockton. A fainter and more local tremor rattled dishes at Lynn, Swampscott, and Salem, Massachu setts, at 12:51 p. m., May 4, but was not recorded on the Harvard seismograph, although only a few miles away. A very strong earthquake at 9:20 p. m., Feb. 28, alarmed the inhabitants generally throughout eastern Canada and New England. Tremors were felt as far south as Virginia and as far west as the Mississippi, but damage was confined to a narrow belt along the St. Lawrence River. The epicenter was probably about half way between Murray Bay on the St. Lawrence and Chicoutimi on the Saguenay River, in an uninhabited portion of the Laurentian upland (Hodgson, Bull. Seismological Soc. Canada. Another sharp tremor was Am., Vol. 15, pp. 84-99). Buildings noted at Kamouraska, Quebec, at were badly damaged and many tombstones overthrown at St. Urbain, Rivière Quelle, and elsewhere upon the alluvial land bordering the St. Lawrence below Quebec. In that city the harbor works on the deep soil and filled ground of the "lower town" were considerably damaged although the quake was not alarming to persons half a mile away on the crystalline rocks of the "upper town." Similar influence of terrane characterized the quake in Boston; panic was narrowly averted in theatres and hotels on the filled ground where formerly were the Back Bay swamps, although in other parts of the city persons were quite unaware of the quake. Estimating the real intensity of this earthquake from the area affected and Slight earthquakes, accompanied the damage in towns scores of miles by rumblings, were reported in the from the epicenter, it appears dynam- vicinity of Middletown and Hartford ically of the same order as in the Connecticut Valley during the Charleston earthquake of 1886. Free- evening of October 29, about 8:00 a. dom from loss of life and the com- m. on Nov. 14, and at 1:20 a. m, paratively slight property damage Nov. 16. the 9:20 p. m., July 26. On October 9 at 8:58 a. m. central and southern New Hampshire was shaken by a local quake of moderate intensity which centered near Lake Winnipe saukee. Windows were broken at Ossipee, and chimneys were cracked at Sandwich, N. H., and Cornish, Me. Seismographs in the eastern states and Canada recorded a moderately se vere quake at 6:00 a. m., October 19, but it has not been possible to deter mine its point of origin from the rec ords and no report of damage nor of sensible vibration has been received. The earthquake may possibly have originated in the region of the St. Lawrence River, but that is by no means certain. CARIBBEAN REGION A tremor severe enough "to crack a few buildings" was reported to have occurred in Kingston, Jamaica, at 12:20 p. m., April 13, and another quake "caused excitement" in the same city shortly before 1:00 a. m., June 15. EASTERN INTERIOR on July 10, about 8:00 a. m., was reported generally throughout central Montana, and again on July 20 at 10:08 a. m. a distinct shock was felt at Helena. Livingston and Bozeman were slightly shaken at 7:50 p. m., August 12, and a faint temblor was reported from the vicinity of Three Forks at 8:45 a. m., August 29. Other tremors in this train of aftershocks were felt at Helena at 3:45 a. m., September 19, at 2:30 a. m., September 30, and early in the morning of October 6. A slight quake was felt at Great Falls on November 8, at 12:07 a. m., and another shock occurred southwest of Sheridan, Wyoming, at 6:45 p. m., November 17. A slight tremor was reported in Syracuse, N. Y., during the afternoon of April 7. A considerable area in western Kentucky, southwestern Ohio, southern Indiana and Illinois was disturbed by three distinct tremors at 10:06, 10:14 and 10:30 p. m., April 26, by the most widespread Southern Kansas, western Oklaquake which has occurred in the homa and the panhandle of Texas exOhio-Mississippi valley in many perienced a tremor about 6:10 a. m., years. The heaviest shocks were reported from the vicinity of Louisville and Owensboro, Ky., and small articles were upset at places as far north as Springfield, Illinois. A local shock broke a few windows in Edwardsville, Illinois, during the night of July 14-15, and about 6:00 a. m., September 2, Evansville, Ind., and adjacent parts of Kentucky were shaken for the second time this year. WESTERN INTERIOR Montana. Central and western Montana and adjacent portions of Idaho and Wyoming were consider ably shaken by sharp quakes at 6:23, 7:05 and 8:40 p. m., June 27. Many persons in Billings, Butte, Anaconda, Great Falls, Missoula, Livingston and Helena were panic stricken, and property damage totaling about $500,000 was caused in and near the Gallatin Valley. A few individuals were injured, but no lives were lost. Passenger trains were hemmed in by landslides along the transcontinental lines, and railroad tunnels were temporarily blocked by rock falls. The most intense shock was felt as far north as Saskatoon and Calgary, Canada, and as far south as Thermopolis and Casper, Wyo. Several aftershocks were recorded, one of which, at 2:20 a. m., June 29, was fairly sharp at Helena. Another July 30. Although the shock was felt over a large area, no damage was caused. PACIFIC COAST REGION was California and Alaska.--A slight quake was felt in Los Angeles and surrounding towns at 10:15 a. m., January 10; no damage was reported. A very slight tremor occurred at Millbrae, Cal., at 1:05 a. m. FebruAlaska ary 10. Southeastern shaken at 1:55 p. m., February 23, by the heaviest tremors which have been felt in that section for many years. The epicenter seems to have been at a point on the coast about 75 miles north of Valdez. A few chimneys were wrecked in Seward, water pipes and telegraph cables were broken, and buildings were rocked by two tremors which together lasted a half minute or more. The Sierra Nevada, northwest of Lake Tahoe, was shaken by several tremors on March 30, between 9:47 p. m. and midnight. The first shock was most severe, but caused no damage. Slight damage was caused by a quake at Calexico, Cal., on April 15, when three shocks were felt between 7:30 and 8:20 a. m. Other quakes shook Ketchikan, Alaska, at 2:30 p. m., April 29, and Los Angeles at 1:25 a. m., May 1. A very feeble shock was reported at Santa Rosa, Cal., May 10, at 5:04 |