Volcanic and tectonic implications of the surface morphology of Mercury are addressed in two separate sections. In Part 1, mercurian scarps, ridges, troughs, and other lineaments are described and classified as planimetrically linear, arcuate, lobate, or irregular. A global pattern of lineaments is interpreted to reflect modification of linear crustal joints formed in response to stresses induced by tidal spindown. Large arcuate scarps on Mercury most likely record a period of compressional tectonism near the end of heavy bombardment. Shrinkage owing to planetary cooling is the mechanism preferred for their production. Two planimetrically lobate escarpments probably formed by uplift along intersecting elements of the global mercurian lineament pattern. One may subsequently have been modified by extrusive igneous activity along its trace. Most irregular scarps inside craters are interpreted to be tectonic features formed in response to local stresses, perhaps induced by subsurface magma movements.
\r\n\r\nLarge linear ridges on Mercury may record a period of volcanism responsible, at least in part, for intercrater plains formation. Linear ridge production is speculatively attributed to accumulation of extruded material along linear vents, and to differential erosion around relatively\r\nresistant dikes intruded into near-surface materials.
\r\n\r\nLinear, open-ended troughs are well-developed in a distinct terrain unit on Mercury characterized by intense modification of pre-existing landforms. Regional trends defined by these troughs are consistent with those of the global mercurian lineament pattern. Combined with their regional setting, this suggests that the troughs formed by differential erosion along linear crustal fractures. A few are radial from nearby large craters, and may be highly modified chains of secondary impact craters.
\r\n\r\nScarps, ridges, and troughs in and around Caloris Basin define trends radial from the basin center and concentric with its rim. A radial system of linear ridges outside Caloris probably reflects the combined effects of ejecta deposition and erosion during the basin-forming event. Planimetrically irregular ridges developed in smooth plains inside Caloris may owe their origin to regional subsidence, perhaps in response to magma withdrawal from below to form smooth plains outside the basin rim. Gravitational readjustment owing to loading by plains material may be responsible for scarp and ridge formation outside Caloris. Finally, isostatic readjustment to basin excavation may have caused regional uplift inside the basin to form a system of planimetrically irregular troughs.
\r\n\r\nIn Part 2, measurements of local normal albedo are combined with computer-generated photometric maps of Mercury to provide constraints on the nature of mercurian surface materials and processes. If the mercurian surface obeys the average lunar photometric function, its normal albedo at 554 nm is .16\u00b1.03. This is roughly 40% higher than the corresponding lunar value, but the difference may be largely attributable to differences in the photometric function s of the two bodies, and to unmodelled effects such as multiple scattering. The existence of relatively bright smooth plains confined to crater floors is most easily reconciled with a volcanic origin for some mercurian smooth plains. Lack of photometric contrast across most large escarpments on Mercury is consistent with the tectonic origin for these features inferred from morphologic studies. Local photometric and transectional relationships in two instances suggest mantling of preexisting topography by younger, perhaps volcanic, material. Brightness of several extremely localized patches in large craters is attributed to enhanced backscatter owing to multiple reflections relative to surrounding plains and craters. These patches are generally \"bluer\" than typical mercurian plains, and some are surrounded by material which is \"redder\" than typical plains. Chemical alteration of crustal rocks, perhaps related to fumarolic activity along impact-induced fractures, is the preferred explanation for these uniquely mercurian features.
", "doi": "10.7907/4c38-xp93", "publication_date": "1977", "thesis_type": "phd", "thesis_year": "1977" }, { "id": "thesis:2718", "collection": "thesis", "collection_id": "2718", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06242009-141311", "primary_object_url": { "basename": "Smith_rsu_1976.pdf", "content": "final", "filesize": 32480924, "license": "other", "mime_type": "application/pdf", "url": "/2718/1/Smith_rsu_1976.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Late-Quaternary Pluvial and Tectonic History of Panamint Valley, Inyo and San Bernardino Counties, California", "author": [ { "family_name": "Smith", "given_name": "Roger Stanley Uhr", "clpid": "Smith-Roger-Stanley-Uhr" } ], "thesis_advisor": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "thesis_committee": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Allen", "given_name": "Clarence R.", "clpid": "Allen-C-R" }, { "family_name": "Smith", "given_name": "George I.", "clpid": "Smith-G-I" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Birman", "given_name": "Joseph Harold", "clpid": "Birman-J-H" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Panamint Valley was filled to overflowing on five, possibly six, separate instances, fed largely by runoff from the Sierra Nevada discharged through Owens and Searles lakes. These high water levels are best represented by uplifted lake terraces and associated deposits at Pleasant Canyon on the, west face of the Panamint Range, where shorelines at five, possibly six, levels have formed with respect to the level of Wingate Pass, (present elevation 1977 \u00b11 feet) into Death Valley. The level of this sill seems to have been tectonically stable, but was permanently raised about 50 feet by a mudflow which poured into the pass during a long-lasting lake stage, herein named Gale Stage. Paired Gale-Stage shorelines, attributed to lake stands stabilized at pre- and post-mudflow sill levels are found throughout Panamint Valley. The lower shoreline is 1.26 times older than the higher, more prominent shoreline, based on 1.26 times greater tectonic deformation at most localities. On the rising range block at Pleasant Canyon, the higher shoreline seems superposed on the lower to form a composite shoreline at 2177\u00b110 feet elevation. Shoreline elevations at Pleasant Canyon (and probable uplift they experienced) are: 2410\u00b110 feet (480\u00b125 feet); 2298\u00b110 (368\u00b125); 2265\u00b110 (335\u00b125); 2177\u00b110 (247\u00b125 to 200\u00b111); 2127\u00b110 (150\u00b111); and 2040\u00b140? (63\u00b141?). If the long-term uplift rate has been constant, the age of each shoreline should be proportional to its height above its sill level. Relatively steady deformation rates throughout Panamint Valley are suggested by the constant proportion (1.26:1.00) of deformation between the older (lower) and younger (higher) Gale-Stage shorelines.\r\n\r\nA radiocarbon age of 31,150\u00b11400 B.P. on snail shells establishes a minimum age for the shoreline at 2127 feet. Extrapolation using steady uplift rates indicates the following youngest-possible ages (in thousands of years) for the other uplifted shorelines: 2410 ft: 100\u00b117; 2298 ft: 77\u00b114; 2265 ft: 70\u00b113; 2177 ft: 52 to 42\u00b17; and 2040 ft?,: 14\u00b110?. The probable age of each lake stage is about 20 per cent greater than its youngest possible age, a judgement based on correlation with the stages of Searles Lake (G.I. Smith, 1968).\r\n\r\nThe higher, younger Gale-Stage shoreline is prominent throughout Panamint Valley. Differential tectonic deformation of this feature amounts to about 370 feet, as established by a maximum elevation of 2190\u00b110 feet on the central Panamint Range to a minimum of 1820\u00b120 at Panamint Valley's north end. Deformation involves differential north- south warping of crustal block on both sides of the Panamint Valley and Ash Hill fault zones, which respectively define the east and west margins of Panamint Valley.\r\n\r\nRight-lateral displacement of Quaternary features along the Panamint Valley fault zone exceeds their vertical, offset. Sixty feet of right-lateral offset have occurred since desiccation of the last, low lake to occupy Panamint Valley (15,000\u00b15,000 B.P.), and cumulative offset of a sheet of monolithologic (landslide?) breccia of Plio-Pleistocene age from its probable source in Wildrose Canyon may total 10,000 to 15,000 feet.\r\n\r\nPanamint Valley is abruptly and massively closed at its north end, where valley-floor deposits appear to underthrust Mesozoic plutonic rocks of Hunter Mountain along a northwest-trending zone which may represent the northwestward continuation of the Panamint Valley fault zone. Along the middle part of this reach of the zone, poorly-sorted (talus?) rubble of sound crystalline boulders underlies a 50 to 100-foot-thick zone of crushed crystalline rock which dips 17 to 35 degrees to the northeast beneath unshattered crystalline rocks. Thrusting may reflect a response to regional northwest-southeast right-lateral shear, possibly imposed upon classical Basin-Range bounding faults. The complex pattern of warping and faulting throughout the rest of Panamint Valley is also consistent with right-lateral shear, and the valley itself may have originated as a right-lateral \"pull apart\".\r\n\r\nThe unusually large volume of deposits along the 2177-foot shoreline suggests correlation with the Sierra Nevada Tahoe glaciation, which is distinguished by unusually large moraines. The small volume of 2127-foot shoreline deposits suggests correlation with the Tenaya glaciation, whose moraines are small. Thus the queried 2040-foot shoreline could represent the Tioga glaciation and the 2410-foot shoreline the Mono Basin glaciation. The 2265 and 2298-foot shorelines may represent early Tahoe events, suggesting that the Tahoe may be divided into early and late phases. Tentative ages of glaciations, based on correlation with pluvial events in Panamint Valley, are (in thousands of years B.P.): Mono Basin: 120\u00b120; Tahoe (early): 92\u00b115 to 78\u00b115; Tahoe (late): 65\u00b113 to 48\u00b110; Tenaya: 38\u00b16; Tioga?: 23\u00b110?.", "doi": "10.7907/W934-HC84", "publication_date": "1976", "thesis_type": "phd", "thesis_year": "1976" }, { "id": "thesis:14013", "collection": "thesis", "collection_id": "14013", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12042020-203212461", "type": "thesis", "title": "Scour and Fill in Ephemeral Streams", "author": [ { "family_name": "Foley", "given_name": "Michael Glen", "clpid": "Foley-Michael-Glen" } ], "thesis_advisor": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "thesis_committee": [ { "family_name": "Vanoni", "given_name": "Vito A.", "clpid": "Vanoni-V-A" }, { "family_name": "Brooks", "given_name": "Norman H.", "clpid": "Brooks-N-H" }, { "family_name": "Dix", "given_name": "Charles Hewitt", "clpid": "Dix-C-H" }, { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The classical concept that mean bed elevation over an entire stream reach is lowered by scour during flood-wave passage and is re\u00adstored by deposition in the waning flood phase (mean-bed scour and fill) can be challenged. The alternative that both scour and fill occur concurrently at different migrating loci within a reach (local scour and fill) is more consistent with published field data. The field and laboratory investigations reported herein suggest that mean-bed scour and fill in a uniform channel is minor compared to local scour and fill caused by bedform migration, and that maximum local scour and fill may occur on the waning flood in some instances.
\r\n\r\nThe field experiment, utilizing a rectilinear array of buried maximum-scour indicators (scour-cords), produced data for contouring of maximum scour and fill in an ephemeral streambed during two floods. In the first flood, 24 cm of scour and fill was measured for a bankfull flow depth of 23 cm.\tIn the second, maximum scour and fill was at least 66 cm for a bankfull flow depth of 34 cm.
\r\n\r\nEstimates of antidune amplitudes for the two floods, based on theoretical models and laboratory and field observations, are 28 to 64 cm and 48 to 97 cm, respectively. This indicates that all scour and fill measured by the scour-cord array could have been caused by antidune migration.
\r\n\r\nLaboratory experiments were conducted in an 18 m-long open-circuit flume with automated sediment and water input-rate controls. A series of experiments in a 26.7 cm-wide sand-bed channel with rigid walls, at grade for a simulated flood patterned after those typical of ephemeral streams, showed that mean-bed scour and fill was less than 3 percent of local scour and fill. For these experiments, mean sand size was 0.3 mm, channel slope was .009, maximum water depth was 40 mm, maximum local scour and fill was 22 mm, and maximum mean-bed scour and fill was 0.6 mm.\tMaximum mean bed elevation variation was thus only two sand-grain diameters. Fill occurred at peak flow followed by scour to the pre-flood mean bed elevation on the waning flood. Maximum local scour and fill took place near the end of the simulated floods, when bedform amplitudes were the greatest.
\r\n\r\nA series of simulated-flood experiments in a sand-bed channel with erodible sand banks showed scour and fill behavior qualitatively similar to that of the rigid-wall channel. Bank erosion, channel meandering, and braiding prevented quantitative scour and fill measurements in these alluvial-bank experiments. Measured flow and bedform parameters and scour and fill data derived from small laboratory scour-chains were compatible with those estimated from the theoretical model used in the field experiment.
", "doi": "10.7907/gbn5-jb14", "publication_date": "1976", "thesis_type": "phd", "thesis_year": "1976" }, { "id": "thesis:5570", "collection": "thesis", "collection_id": "5570", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03042010-080311245", "primary_object_url": { "basename": "Wood_sh_1975.pdf", "content": "final", "filesize": 11768638, "license": "other", "mime_type": "application/pdf", "url": "/5570/1/Wood_sh_1975.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Holocene Stratigraphy and Chronology of Mountain Meadows, Sierra Nevada, California", "author": [ { "family_name": "Wood", "given_name": "Spencer Hoffman", "clpid": "Wood-Spencer-Hoffman" } ], "thesis_advisor": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Valley-fill deposits, exposed by Twentieth-Century dissection of a number of meadows on the west slope of the southern Sierra Nevada, contain a stratigraphic record strongly affected by secular variations in watershed hydrology during the Holocene. Meadows are situated in low gradient reaches, adaquately supported by seepage water, where fine textured materials accumulate under present hydrologic conditions. Meadows do not necessarily owe their origin to glacial modification of drainage. Many meadows have formed in both glaciated and unglaciated valleys by a water table rise in valley-fill deposits.\r\n\r\nGround water in any meadow drainage basin is annually recharged by snowmelt. Significant evapotranspiration by meadow plants causes diurnal fluctuations of growing-season water tables on the order of 0.2 to 0.5 ft and seasonal fluctuations of 2 to 4 ft. Growing-season water-table depths are characteristically different for the two major plant communities, being usually shallower than 2 feet for meadows, and deeper than 4 ft for conifer forests. This relationship and a ground-water model are used to interpret paleohydrologic variations recorded in valley-fill stratigraphy.\r\n\r\nStratigraphy, radiocarbon dating, and tephrachronology indicate the following sequence in upper tributary valleys of the montane belt. Pre-Holocene cobbly alluvium rests upon bedrock. A paleosol developed upon this alluvium between 10,200 and 8700 radiocarbon years B.P., records an early post-glacial climatic interval that established forests in the present upper montane belt. The overlying sequence of coarse loamy materials associated with in situ conifer stumps indicates one or more intervals of good soil drainage and dry valley-bottom conditions between 8700 and 1200 years B.P. At some sites there is an abrupt change from orest soils to overlying wet-meadow deposits dated 2500 years at some sites and 1200 years at others, suggesting many meadows originated coincidentally with neoglaciation in the Sierras. A water-table rise of a few feet, resulting from late melting snows, could cause the change from forest to meadow conditions. Meadow deposits are composed of organic-rich, sandy-loam, topsoil layers intercalcated with sheets of well-sorted sandy gravels deposited by flood flows with recurrence intervals greater than 50 years.\r\n\r\nA plot of upstream catchment area and valley gradient for dissected and undissected meadows indicates the geomorphic domain of unstable meadows subject to gully erosion under present hydrologic conditions on the Sierra west slope.\r\n\r\nTwo pumiceous tephra layers, widespread in meadow topsoils of the southern Sierra, are radiocarbon dated and attributed to tephraringed eruptive centers at opposite ends of the Mono-Inyo Crater chain of eastern California. Tephra 1, characterized by sanidine microphenocrysts and Sr content of 215 ppm, erupted 720 years B.P. Distribution of this tephra is confined to a south trending lobe extending 120 miles over the Sierra from the upper San Joaquin drainage to the Little Kern drainage. Trace element analysis of tephra 1 best match those of the tephra-ringed obsidian flow just south of Deadman Creek in the Inyo Craters. Tephra 2, characterized by a lack of microphenocrysts and Sr contents less than 20 ppm erupted from one of the northern Mono Craters eruptive centers. These two tephras appear to represent the most recent explosive eruptions of magma from this 40-km long chain of Holocene volcanoes.\r\n", "doi": "10.7907/HQEG-6769", "publication_date": "1975", "thesis_type": "phd", "thesis_year": "1975" }, { "id": "thesis:1396", "collection": "thesis", "collection_id": "1396", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04162003-095459", "primary_object_url": { "basename": "Hooke_rl_1965.pdf", "content": "final", "filesize": 17907409, "license": "other", "mime_type": "application/pdf", "url": "/1396/1/Hooke_rl_1965.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Alluvial Fans", "author": [ { "family_name": "Hooke", "given_name": "Roger LeBaron", "clpid": "Hooke-Roger-LeBaron" } ], "thesis_advisor": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "NOTE: Text or symbols on renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\n\r\nAlluvial fans were studied in the field, largely in the desert regions of California, and in the laboratory. Field study consisted of detailed mapping of ages and sizes of debris, channel patterns, and deposits of different types on parts of four fans, and reconnaissance work on over 100 additional fans. Reconnaissance generally consisted of outlining the fan, noting material size and channel patterns, and measuring a few slopes. In the laboratory small alluvial fans were built of mud and sand transported through a channel into a five-foot square box under controlled conditions.\r\n\r\nMaterial is transported to fans by debris flows or water flows which follow the main channel. This channel is generally incised at the fanhead, because there water is able to transport on a lower slope the material deposited earlier by debris flows. Since the main channel at the fanhead has a lower slope than the adjacent fan surface, it emerges onto the surface near a midfan point herein called the intersection point. On the laboratory fans most deposition above the intersection point is by debris flows that exceed the depth of the incised channel. Fluvial deposition dominates below the intersection point. This is also inferred to be true on natural fans.\r\n\r\nFans deficient in fine material may have so high an infiltration rate that even moderately large discharges are completely absorbed before reaching the toe of the fan. Under these conditions the coarse debris in transport is deposited as lobate masses on the fan. In many respects these deposits resemble and may, in the past, have been mistaken for debris-flow deposits.\r\n\r\nThe empirical relationship between fan area, A[subscript f], and drainage-basin area, A[subscript d] = cA[subscript d][superscript n] has been recognized previously (Bull, 1964; Denny, 1965). The present study suggests that this relationship results from a tendency toward a quasi steady-state between coalescing fans in the same lithologic, tectonic, and geographic environment. The quasi steady-state exists when all fans are increasing in thickness at the same rate. If rates differ, the areas of the fans will change to approach a quasi steady-state. The rate of deposition is determined by the influx of debris, which is a function of drainage basin area. The exponent [...] is less than unity because a storm of a given recurrence interval is less likely to envelop a large drainage basin than a small one. The coefficient [...] is a function of the lithologic, tectonic, and geographic environment.\r\n\r\nRates of deposition on fans may be estimated from this relationship using Langbein and Schumm's (1958) data on sediment yield as a function of precipitation. A typical average rate is on the order of one foot per 1,000 years. If a long-term tectonic process is superimposed upon the quasi steady-state relationship between fans in the same lithologic and geographic environment, the rate of deposition may be used to estimate the rate and nature of the tectonic process. As an example, the difference in depositional rates on opposite sides of Death Valley suggests a present rate of eastward tilting of 0.018 degrees/1000 years.\r\n\r\nThe slope of an alluvial fan is determined primarily by debris size and water discharge. Large fans have larger drainage basins and hence larger discharges than small fans. Consequently fan slope generally decreases with increasing fan area.\r\n\r\nPhotographic materials on pages 16, 31, 33, 55, 63, 64, and 81 are essential and will not reproduce clearly on Xerox copies. Photographic copies should be ordered.\r\n", "doi": "10.7907/4KN6-1E95", "publication_date": "1965", "thesis_type": "phd", "thesis_year": "1965" }, { "id": "thesis:1068", "collection": "thesis", "collection_id": "1068", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03232006-104828", "primary_object_url": { "basename": "Benson_cs_1960.pdf", "content": "final", "filesize": 27289939, "license": "other", "mime_type": "application/pdf", "url": "/1068/1/Benson_cs_1960.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Stratigraphic Studies in the Snow and Firn of the Greenland Ice Sheet", "author": [ { "family_name": "Benson", "given_name": "Carl S.", "clpid": "Benson-Carl-S" } ], "thesis_advisor": [ { "family_name": "Kamb", "given_name": "W. Barclay", "clpid": "Kamb-W-B" }, { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nThe Greenland ice sheet is treated as a monomineralic rock formation, primarily metamorphic, but with a sedimentary veneer of snow and firn. This sedimentary member is perennial above the firn line, and the classical methods of stratigraphy and sedimentation can be profitably applied to it.\r\n\r\nDuring a 4-year period 146 pit studies and 288 supplementary Rammsonde profiles were made along 1100 miles of over-snow traverse (Fig.1). Temperature, density, ram hardness, and grain size were measured in the strata exposed in each pit.\r\n\r\nStratification of snow results from variations in the conditions of deposition and is emphasized by subsequent diagenesis. Summer layers are coarser-grained and have generally lower density and hardness values than winter layers; they may also show evidence of surface melt. The onset of fall is usually identified by an abrupt increase in density and hardness accompanied by a decrease in grain size. This stratigraphic discontinuity is used as the annual reference plane.\r\n\r\nStrata in the upper 10 to 20 meters compose a succession of annual sequences which are preserved in recognizable form for at least several decades. Correlation of annual layers between pits, spaced 10 to 25 miles apart along the traverse of Figure 1, gives a picture of annual accumulation during the past 5 to 20 years for western Greenland between 69 and 77\u00b0N. The control established by these data, together with information from earlier expeditions (primarily those of Koch-Wegener and DeQuervain) and from permanent coastal meteorological stations, have been used to make a map showing the distribution of gross annual accumulation, essentially the equivalent of annual precipitation, for the entire ice sheet (Fig. 30). In general, the accumulation contours follow the north-south trend of the coast lines, with extremes of less than 10 cm H2O in the northeast and more than 90 cm H2O per year in the south; the average for the ice sheet is 34 cm H2O per year. The zone of maximum precipitation lies close to the coast in two regions, one on the east coast between Angmagssalik and Scoresbysund, the other on the west coast between Upernavik and Thule.\r\n\r\nIn addition to the existence of a useful stratigraphic record four diagenetic facies are recognized on the ice sheet.\r\n\r\n(1) The ablation facies extends from the outer edge, or terminus, of the glacier to the firn line. The firn line is the highest elevation to which the annual snow cover recedes during the melt season.\r\n\r\n(2) The soaked facies becomes wet throughout during the melting season and extents from the firn line to the saturation line, i.e., the uppermost limit of complete wetting. The saturation line is the highest altitude at which the 0\u00b0C isothermal surface penetrates to the melt surface of the previous summer.\r\n\r\n(3) The percolation facies is subjected to localized percolation of melt water from the surface without becoming wet throughout. Percolation can occur in snow and firn of sub-freezing temperatures with only the pipe-like percolation channels being at the melting point. A network of ice glands, lenses, and layers forms when refreezing occurs. This facies extends from the saturation line to the upper limit of surface melting, the dry-snow line. Negligible soaking and percolation occur above the dry-snow line.\r\n\r\n(4) The dry-snow facies includes all of the glacier lying above the dry-snow line, and negligible melting occurs in it.\r\n\r\nThe saturation line can be identified by discontinuities in temperature, density, and ram hardness data, and it may also be located by examination of melt evidence in strata exposed on pit walls. It is as sharply defined as the firn line; but the dry-snow line, although determined by the same methods, is an ill-defined transition zone 10- to 20-miles wide.\r\n\r\nThe facies represent a response to climate, therefore changes in the location of facies boundaries may be used as indicators of secular climatic change. Since facies are not restricted to the Greenland ice sheet, they provide the basis for a general classification of glaciers. This \"facies classification\" is areal in nature and gives a greater resolution of characteristics than Ahlmann's \"geophysical classification.\" In particular, the \"facies classification\" permits subdivision of large glaciers which span the entire range of environments from temperate to polar. Ahlmann's useful distinction between temperate and polar glaciers takes on new meaning in the light of glacier facies. Thus, a temperate glacier exhibits only the two facies below the saturation line whereas one or both of the facies above the saturation line are present on polar glaciers. An attempt has been made to map the distribution of facies on the Greenland ice sheet (Fig. 48).\r\n\r\nThe distribution of mean annual temperature on the ice sheet may be approximated by gradients with respect to altitude and latitude of 1\u00b0C/100m and 1\u00b0C per degree latitude respectively. The altitude gradient is controlled by strong outgoing radiation, producing deep inversions and katabatic winds. The katabatic winds are warmed adiabatically as they descend along the surface of the ice sheets and this is the primary control determining the temperature gradient along the snow surface. The latitude gradient is based on temperature measurements made above 2000 m on the ice sheets and on average values from meteorological stations spanning 20\u00b0 of latitude on the west coast. A contour map of isotherms based on these gradients compares well with temperature values obtained from pits on the ice sheet. (Fig. 40).\r\n\r\nThe densification of snow and firn is discussed for the case where melting is negligible. The assumption is that accumulation remains constant at a given location and, under this assumption, the depth-density curve is invariant with time as stated by Sorge's law. As a layer is buried it moves through a pressure gradient under steady-state conditions, and it is assumed that the decrease in pore space with increasing load is simply proportional to the pore spaces, i.e., [...] where [...] = specific volume of firn ([...] = firn density), [...] = specific volume of ice = 1.09 cm3/g, [...] = load at depth z below the snow surface and m = a constant which depends on the mechanism of densification. The depth-density equation obtained from equation 8 is [...] where K = [...], [...] = void ratio for snow of density [...], and [...] = void ratio for snow of density [...], [...] = density of snow when [...] = 0.\r\n\r\nThe consequences of the assumption in equation 8 compare favorably with observation. A fundamental change in the mechanism of densification is recognized within 10 m of the snow surface. The concept of a \"critical density\" is introduced. Before the density of snow attains the critical value it is compacted primarily by packing of the grains. The critical density represents the maximum value obtainable by packing and further compaction must proceed by other mechanisms. The rate of change of volume with increasing load decreases by a factor of 4 when the critical density is exceeded. The same equations hold in the case where melt is not negligible but the rates of densification are higher.\r\n\r\nBauer's (1955) estimate for the balance of the ice sheet is revised. Two corrections are applied: (1) the average annual accumulation value of 31 cm H2O originally estimated by Loewe (1936) is revised to 34 cm H2O as a result of this study; (2) the relative areas of ablation and accumulation zones in Greenland north of 76\u00b0N are more accurately defined. The net result is a slightly positive balance which is interpreted to mean that the Greenland ice sheet is essentially in equilibrium with present day climate.\r\n", "doi": "10.7907/G7V2-0T57", "publication_date": "1960", "thesis_type": "phd", "thesis_year": "1960" }, { "id": "thesis:691", "collection": "thesis", "collection_id": "691", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02212006-085518", "primary_object_url": { "basename": "Shreve_rl_1959.pdf", "content": "final", "filesize": 5835535, "license": "other", "mime_type": "application/pdf", "url": "/691/1/Shreve_rl_1959.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Geology and Mechanics of the Blackhawk Rockslide, Lucerne Valley, California", "author": [ { "family_name": "Shreve", "given_name": "Ronald Lee", "clpid": "Shreve-Ronald-Lee" } ], "thesis_advisor": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Blackhawk Mountain, a resistant mass of marble thrust northward over uncemented sandstone and weathered gneiss, rises above southeastern Lucerne Valley at the eastern end of the rugged 4000-foot escarpment that separates the San Bernardino Mountains on the south from the Mojave Desert on the north. Spread out on the alluvial apron at the foot of the mountain is the Blackhawk rockslide, a lobe of nearly monolithologic marble breccia 30 to 100 feet thick, 2 miles wide, and nearly 5 miles long. At least two earlier similar but smaller rockslides have occurred in the area.
\r\n\r\nThe rocks of the area comprise late Tertiary and Quaternary fanglomerates and breccias derived mainly from the gneiss, quartzite, Carboniferous marble, and Cretaceous quartz-monzonite of the San Bernardino Mountains. Uplift of Blackhawk Mountain occurred in two stages after deposition of the older fanglomerates and breccias: the first by over-thrusting from the south, and the second by monoclinal folding along a northwest-trending axis.
\r\n\r\nGeological evidence in the area shows that the Blackhawk rockslide traversed the gently inclined alluvial slope as a nearly nondeforming sheet of breccia moving more than 50 miles per hour. The hypothesis that compressed air, rather than water or mud, constituted the lubricating layer on which the breccia sheet slid qualitatively explains all of the principal physical features of the slide lobe. Theoretical analysis of the flow in the lubricating air layer indicates the quantitative feasibility of the air-lubrication hypothesis for the Blackhawk slide.
", "doi": "10.7907/T496-QF62", "publication_date": "1959", "thesis_type": "phd", "thesis_year": "1959" }, { "id": "thesis:2607", "collection": "thesis", "collection_id": "2607", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06152006-081525", "primary_object_url": { "basename": "Meier_mf_1957.pdf", "content": "final", "filesize": 10124167, "license": "other", "mime_type": "application/pdf", "url": "/2607/1/Meier_mf_1957.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Mode of Flow of Saskatchewan Glacier, Alberta, Canada", "author": [ { "family_name": "Meier", "given_name": "Mark Frederick", "clpid": "Meier-Mark-Frederick" } ], "thesis_advisor": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Research in 1952-54 on Saskatchewan Glacier was directed toward the measurement of velocity on the surface and at depth, the surface and bedrock topography, ablation, and structures produced by flow. These field data are used to test current theories of flow and to derive new conclusions about the flow of a valley glacier.
\r\n\r\nPositions in space of 51 velocity stations fixed in the ice were computed from triangulation surveys. Summer velocities are generally greater than yearly velocities. Short interval (1/2-1 day) observations recorded great velocity fluctuations and occasional backward movements. Some of these fluctuations represent domains not over 100 feet in extent. Dispersion values indicate that jerkiness is probably due to irregular shearing and is not predominantly perpendicular to crevasses. Dispersion of velocity decreases with increasing time intervals of measurement. Maximum surface velocity of 383 fpy occurs at the firn limit; velocity decreases unevenly along the midglacier line to 12 fpy at the terminus. Velocity vectors plunge below the surface along the centerline from above the firn limit to 1.3 miles below. Further downglacier the vectors rise out from the surface and the angular divergence increases both downglacier and toward the margins. The flow of ice toward the surface is constant at 10 fpy in the lower 3 miles. Rates of surface lowering computed from these data and ablation data agree roughly with independently measured thinning.
\r\n\r\nVelocity gradients in an area of detailed study are analyzed to determine the surface strain rate field. Deformation is largely caused by the transverse gradient of the longitudinal velocity. Longitudinal and transverse extensions and compressions were measured. One principal strain rate trajectory lies along the flow centerline; a trajectory of maximum shearing strain rate parallels the valley wall at the margin.
\r\n\r\nVelocity to a depth of 140 feet decreases exponentially. The flow law of ice is determined by an analysis of this short vertical profile and a transverse velocity profile on the surface. The two sets of data give consistent results which agree with results from other glaciers, and suggest that the flow law is unaffected by either hydrostatic pressure or extending or compressing flow. The strain rate cannot be expressed as a simple power function of the stress. A viscous-like flow appears to predominate at low stresses. Above a shear stress of 0.7 bar the flow velocity changes much more rapidly with slight changes in stress.
\r\n\r\nThe derived flow law is used to compute velocity as a function of depth and the mass-budget. These results show that the ice currently being supplied to the surface is not as great as the surface ablation but is just sufficient to keep the glacier thinning at an unchanged rate in time. Computed streamlines parallel the bedrock channel closely.
\r\n\r\nThree main classes of features in the ice are distinguished: (1) primary sedimentary layering, (2) secondary flow foliation and (3) secondary cracks and crevasses. Primary stratification is flat-lying in general but wrinkled longitudinally in detail. Foliation generally dips steeply, strikes longitudinally, and shears other structures. However, some foliation attitudes do not relate to measured directions of maximum shearing strain rate at the point of observation or at any conceivable point of origin. The orientation of the most prominent set of cracks agrees approximately with measured trajectories of principal compressing strain rate. Other minor sets of cracks are related to trajectories of maximum shearing strain rate.
", "doi": "10.7907/Q1QN-XP58", "publication_date": "1957", "thesis_type": "phd", "thesis_year": "1957" }, { "id": "thesis:1735", "collection": "thesis", "collection_id": "1735", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05122003-112509", "primary_object_url": { "basename": "Rigsby_gp_1953.pdf", "content": "final", "filesize": 7207906, "license": "other", "mime_type": "application/pdf", "url": "/1735/1/Rigsby_gp_1953.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Studies of Crystal Fabrics and Structures in Glaciers", "author": [ { "family_name": "Rigsby", "given_name": "George Pierce", "clpid": "Rigsby-George-Pierce" } ], "thesis_advisor": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Optical orientation of approximately 5000 ice crystals was determined on the Emmons Glacier in 1950, the Malaspina Glacier in 1951, and the Saskatchewan Glacier in 1952, by means of a 6-inch universal stage mounted between crossed polaroid sheets. The crystals measured were 0.2-6 inches across, and from three to eighty were included in each 4 ? x 6-inch thin-section. The optic axes when plotted on a Schmidt equal-area projection, form consistent patterns which appear to be related to the foliation in the ice. The patterns usually feature strong maxima at the corners of diamond shaped quadrangles. Concentrations of axes as high as 26 per cent in 1 per cent of the area were recorded.\r\n\r\nTwo possible mechanisms for producing common orientation of the crystals in glacier ice seem plausible. One is ?instantaneous recrystallization? by means of which the atoms in a lattice become energized under stress and rearrange themselves into more comfortable positions. The second is the growth of crystals favorable to deformation on glide planes at the expense of those which are unfavorably oriented for gliding and consequently become strained and develop higher free energy.\r\n\r\nFrom the study of fabric patterns in glaciers it seems likely that the two crystals are oriented in such a way as to allow gliding either on two glide planes other than the well-known basal plane, or on the basal glide plane with the pattern later being changed by recrystallization, possibly by an ordered response within the crystals to the relaxation of stresses. This might be compared to annealing behavior in metals.\r\n\r\nIt is postulated that ?solid flow? occurs in ice by deformation on glide planes and continuous recrystallization with migration of grain boundaries as local stresses on each crystal slowly change. The preferred orientation of crystals is probably developed by growth of crystals favorably oriented for gliding at the expense of the others.", "doi": "10.7907/03RC-6663", "publication_date": "1953", "thesis_type": "phd", "thesis_year": "1953" }, { "id": "thesis:10685", "collection": "thesis", "collection_id": "10685", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02082018-131502507", "primary_object_url": { "basename": "Nelson_RL_Major_1952.pdf", "content": "final", "filesize": 41103656, "license": "other", "mime_type": "application/pdf", "url": "/10685/1/Nelson_RL_Major_1952.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "A Study of the Seismic Waves SKS and SKKS. Glacial Geology of the Frying Pan River Drainage, Colorado", "author": [ { "family_name": "Nelson", "given_name": "Robert Leslie", "clpid": "Nelson-Robert-Leslie" } ], "thesis_advisor": [ { "family_name": "Gutenberg", "given_name": "Beno", "clpid": "Gutenberg-B" }, { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "[Major Thesis Abstract]
\r\n\r\nArrival times, amplitudes, and periods of the seismic phases SKS and SKKS have been investigated for normal, intermediate, and deep earthquakes recorded at Pasadena and Huancayo, Peru. New observed time\u00ad-distance curves are constructed for depths of < 60, 100, 200, and 600 kilometers. Travel-times for the core have been calculated from normal shock time data. Slight modification of wave velocity just inside the core and of travel times within the core are suggested. Calculated travel times of SKS, SKKS, and SKKKS are in good agreement with observations.
\r\n\r\nEnergy parameters determined from observed ampli\u00adtude/period ratios are found in only fair agreement with those calculated from theory. Observed energies are too large for most of the phase components and depths considered. The horizontal components of SKKS over the whole distance range, and of SKS at \u0394 < 100\u00b0for all depths, yield observed energies less than those pre\u00addicted by theory. Both discrepancies are at least qual\u00aditatively explained by a proposed non-spherical distribution of shear strain about the fault source, and by . abnormal absorption in the outer 700 kilometers of the core. A period increase with epicentral distance for SKS and SKKS is best explained by selective absorption in this same zone.
\r\n\r\nAnomalous observed energies, as a function of epi\u00adcentral location, can also be accounted for by the proposed non-spherical distribution of energy. A similar regional phase-period dependence is considered in terms of finite faulting velocities. Times, energies, and periods of multiple SKS phases for the depths studied are presented. No single hypothesis commensurate with all observed conditions is found, but the phases pSKS and sSKS for normal shocks are probably represented.
\r\n\r\n[Minor Thesis Abstract]
\r\n\r\nOn the west flank of the Sawatch Range, Colorado, evidence is found for six distinct glacial advances. One glaciation is pre-Wisconsin, four are Wisconsin, and one post-Wisconsin in age. In addition to end and lateral moraines of each advance, terrace remnants of six valley trains were identified and studied for a distance of 25 miles along Frying Pan River and its major tributaries. Elevations above stream level of these outwash terraces are 400\u00b150, 90-120, 40-50, 20-30, 12-17, and 6-8 feet. Five of the tributary valleys contained ice streams which did not join the trunk Frying Pan glacier during the Wisconsin stage.
\r\n\r\nAn extensive review and testing of the numerous criteria used to distinguish deposits of multiple glaciations shows that nine of these criteria can conveniently be expressed in parameters indicative of relative age. Estimates based on these criteria, coupled with a recent radiocarbon dating of late Mankato till in the Midwest, yield the following approximate ages for deposits of the six glaciations in Frying\r\nPan Valley: 230,000, 63,000, 46,000, 17,000, 11,500, and 5,750 years. The accuracy and reliability of the procedure used cannot be evaluated without further absolute Carbon-14 age determination.
\r\n", "doi": "10.7907/WWWD-0T60", "publication_date": "1952", "thesis_type": "phd", "thesis_year": "1952" }, { "id": "thesis:5656", "collection": "thesis", "collection_id": "5656", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03302010-085636751", "primary_object_url": { "basename": "Campbell_rb_1951.pdf", "content": "final", "filesize": 7209531, "license": "other", "mime_type": "application/pdf", "url": "/5656/1/Campbell_rb_1951.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Continental Glaciation in the Glenlyon Area, Pelly River District, Yukon, Canada", "author": [ { "family_name": "Campbell", "given_name": "Richard Bradford", "clpid": "Campbell-Richard-Bradford" } ], "thesis_advisor": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The Glenlyon area in central Yukon is bounded by 62\u00b0 \r\nand 63\u00b0N and 134\u00b0 and 136\u00b0W. It is part of the Yukon Plateau, a mature upland surface surmounted by isolated peaks and small ranges, and dissected by deep, young valleys. Features of glacial erosion and deposition ore such that the direction of flow and the upper limit or the last glaciation can be determined from them.\r\n\r\nIce flowed into central Yukon from three sources, Selwyn\r\nMountains to the east, Cassiar mountains to the southeast, \r\nand the Coast and St. Elias mountains to the south. Ice \r\nmoved into the Glenlyon area from the first two of these \r\nsources and apparently the maximum stages of these two gla\r\ncial advances were not synchronous, but Selwyn ice was active last. In this area, many higher mountains and hills projected above the ice surface as nunataks. In detail, topography altered the direction of ice flow, ice thickness and extent.\r\n\r\nEvidence from adjacent parts of Yukon suggest two or possibly three glaciations but only the last has been recognized in the Glenlyon area although this could not have escaped glaciation in earlier stages. The large glaciers of central Yukon developed by windward building in contrast with the Cordilleren ice sheet in central British Columbia which developed on the lee of the Coast Range.", "doi": "10.7907/GQNK-GQ14", "publication_date": "1951", "thesis_type": "masters", "thesis_year": "1951" }, { "id": "thesis:8684", "collection": "thesis", "collection_id": "8684", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10092014-103732963", "primary_object_url": { "basename": "Steenson_bo_1951.pdf", "content": "final", "filesize": 12050814, "license": "other", "mime_type": "application/pdf", "url": "/8684/1/Steenson_bo_1951.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Radar Methods for the Exploration of Glaciers", "author": [ { "family_name": "Steenson", "given_name": "Bernard Owen", "clpid": "Steenson-Bernard-Owen" } ], "thesis_advisor": [ { "family_name": "Pickering", "given_name": "William Hayward", "clpid": "Pickering-W-H" }, { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The problem of finding the depths of glaciers and the current methods are discussed briefly. Radar methods are suggested as a possible improvement for, or adjunct to, seismic and gravity survey methods. The feasibility of propagating electromagnetic waves in ice and the maximum range to be expected are then investigated theoretically with the aid of experimental data on the dielectric properties of ice. It is found that the maximum expected range is great enough to measure the depth of many glaciers at the lower radar frequencies if there is not too much liquid water present. Greater ranges can be attained by going to lower frequencies.
\r\n\r\nThe results are given of two expeditions in two different years to the Seward Glacier in the Yukon Territory. Experiments were conducted on a small valley glacier whose depth was determined by seismic sounding. Many echoes were received but their identification was uncertain. Using the best echoes, a profile was obtained each year, but they were not in exact agreement with each other. It could not be definitely established that echoes had been received from bedrock. Agreement with seismic methods for a considerable number of glaciers would have to be\r\nobtained before radar methods could be relied upon. The presence of liquid water in the ice is believed to be one of the greatest obstacles. Besides increasing the attenuation and possibly reflecting energy, it makes it impossible to predict the velocity of propagation. The equipment used was far from adequate for such purposes, so many of the difficulties could be attributed to this. Partly because of this, and the fact that there are glaciers with very little liquid water present, radar methods are believed to be worthy of further research for the\r\nexploration of glaciers.
", "doi": "10.7907/3YY8-XC87", "publication_date": "1951", "thesis_type": "phd", "thesis_year": "1951" }, { "id": "thesis:5551", "collection": "thesis", "collection_id": "5551", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02262010-085815097", "primary_object_url": { "basename": "Rigsby_gp_1950.pdf", "content": "final", "filesize": 4329033, "license": "other", "mime_type": "application/pdf", "url": "/5551/1/Rigsby_gp_1950.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Glaciological Studies in the St. Elias Range, Canada", "author": [ { "family_name": "Rigsby", "given_name": "George Pierce", "clpid": "Rigsby-George-Pierce" } ], "thesis_advisor": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The glaciological and geologic studies of 1948 in the St. Elias Range by a group from the California Institute of Technology were made possible by the Arctic Institute of North America and research grants from the Office of Naval Research, American Alpine Club and the California Institute. Walter A. Wood, director of the New York office of Arctic Institute, led the entire operation, and Robert P. Sharp of the California Institute of Technology directed the scientific research.
\r\n\r\nThe purpose of the expedition was to make studies of the physics of ice, snow and glaciers, as well as to gather specific information on accumulation, ablation, temperature, movement, density, depth and compaction of the firn in the Seward firn field. It is also hoped that first hand study of existing glaciers will produce a better understanding of past happenings in areas from which glaciers have disappeared. Part of the program consisted of checking the published conclusions of other workers in glaciology as well as attempting to add something to this science. The possibility that radar might be a better and faster means of determining the thickness of a body of ice was investigated, and a check of the radar results by seismic methods was planned. Bernard O. Steenson, a graduate student in Electrical Engineering at the California Institute of Technology, built and operated the radar equipment. F. Beach Leighton, a graduate student in the Division of Geological Sciences at the same institution, worked with meltwater, ablation and accumulation, while the author studied temperature and density of the firn, glacier movement and bedrock geology of the area. The seismic operations were under the direction of Donald J. Salt of the University of Toronto, Canada.
\r\n", "doi": "10.7907/MX3E-DB92", "publication_date": "1950", "thesis_type": "masters", "thesis_year": "1950" }, { "id": "thesis:5597", "collection": "thesis", "collection_id": "5597", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03122010-103205758", "primary_object_url": { "basename": "Leighton_fb_1949.pdf", "content": "final", "filesize": 13149833, "license": "other", "mime_type": "application/pdf", "url": "/5597/1/Leighton_fb_1949.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Contributions to the Glaciology of the Seward Ice Field, Canada, and the Malaspina Glacier, Alaska", "author": [ { "family_name": "Leighton", "given_name": "Freeman Beach", "clpid": "Leighton-Freeman Beach" } ], "thesis_advisor": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Certain phenomena of the Seward Ice Field and the Malspina Glacier as observed in the summer of 1948 are interpreted in the light of glaciologic literature.\r\n\r\nInferences on glacier regimen are drawn from accumulation and ablation measurements. The efficacy of the ablation factors is discussed and analogies are deduced by comparing ablation and meteorological data with those collected by Scandinavian glaciologists on the Vatnajokull,\r\nIceland. The meteorological factors play an overwhelmingly important part in ablation on the ma1uspina Glacier and probably retain their advantage over radiation at a higher elevation on the Seward Ice Field.\r\n\r\nDistinctions are made between indirect, internal, net end gross ablation. The formation of a glacier water table, and the incidence and dissipation of the winter cold wave on the Seward are discussed.\r\n\r\nTwo contrasting types of differential melt-depressions were noted on the Seward, inclined underwater ice wells and vertical wells not under water. Previous theories of ice- well formation are critically analyzed. The deepening of the ice wells beyond the depth at which the depression is shaded from the sun is believed to be produced by diffuse radiation, with reflected direct radiation playing a minor role. Experiments with artificial ice blocks attest to the\r\nimportance of vertical gravity settling of debris in ice wells and fail to account for the inclination of the underwater ice wells.\r\n\r\nMelt-water movement studies were undertaken during a period in July and August. The quantities of melt-water percolating through the firn were measured at various depths and are compared to the ablation record, the meteorological record, and to the time of day in this paper. There is little correlation between the daily melt-water record and the daily sunshine and ablation records. Air temperature is the most significant index of melt-water production. However, the average maximum temperature was reached between 11 and 12 A.M and the average hourly maximum melt-water collected was recorded between 5 and 6 P.M. The fact that the upper firm layers produced less water than deeper firn layers is evidently due to the greater capillary flow and less concentration of melt-water in the upper firn.\r\n\r\n", "doi": "10.7907/RTYV-8D93", "publication_date": "1949", "thesis_type": "masters", "thesis_year": "1949" }, { "id": "thesis:5604", "collection": "thesis", "collection_id": "5604", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03152010-105757471", "primary_object_url": { "basename": "Dort_w_1948.pdf", "content": "final", "filesize": 13698138, "license": "other", "mime_type": "application/pdf", "url": "/5604/1/Dort_w_1948.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "The Geology of a Portion of Eastern Ventura Basin, California", "author": [ { "family_name": "Dort", "given_name": "Wakefield, Jr.", "clpid": "Dort-Wakefield-Jr" } ], "thesis_advisor": [ { "family_name": "Jahns", "given_name": "Richard H.", "clpid": "Jahns-R-H" }, { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "thesis_committee": [ { "family_name": "Unknown", "given_name": "Unknown" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The eastern part of the Ventura Basin has\r\naroused the interest of geologists, professionals and\r\namateurs alike, for almost one hundred years. Much of\r\nthis attention has stemmed from the discovery of small\r\ndeposits of gold, and the completion of a few producing\r\noil wells within the area. Of more academia interest\r\nare some problems presented by the stratigraphy and\r\npaleontology of the region. These questions have been\r\ndebated at length by Stirton, Maxson, Kew, Jahns, and\r\nothers. References to these discussions are provided in\r\nthe bibliography.
\r\n\r\nThe Ventura Basin is a structural trough\r\nlying in the Transverse Range division of the Coast\r\nRange province of California. As shown in Figure 1, the\r\nspecific part of the Ventura Basin discussed in this\r\nreport lies somewhat east of the center of the valley,\r\nand northeast of the town of Newhall. The area is well\r\nwithin the boundaries of Los Angeles County, and is easily accessible by US Highway 6, as well as by\r\nnumerous state and county roads. It lies 30 miles from the Los Angeles Civic Center.
\r\n\r\nThis report deals with an area of approximately\r\ntwenty-six square miles, comprising parts of the Saugus,\r\nNewhall, Sylmar and Humphries quadrangles mapped by the\r\nUnited States Geological Survey. It is essentially\r\nbounded by Bouquet, Placerita, Soledad, and Mint Canyons.\r\nThe settlements of Saugus-Pardee, Honby, Solamint,\r\nSt. Johns, and Forest Park are included within these\r\nboundaries.
\r\n", "doi": "10.7907/JB4H-2S16", "publication_date": "1948", "thesis_type": "masters", "thesis_year": "1948" } ]