Summit Altitude Research Articles

Morphometric characteristics of glacial cirques and former glaciers in the Geyik Mountains, Western Taurus, Türkiye

Using the Glacier reconstruction (GlaRe) toolbox, reconstructions of former glaciers in the Geyik Mountains, part of the Taurus Mountain system in southern Türkiye, show that an area of 132.5 km2 was glaciated in the last major glaciation, which left clear terminal and hummocky moraines. Glaciers were 1.4 to 12 km long and those from 49 cirques merged to form a broad 75 km2 piedmont glacier in the Namaras Valley, up to 400 m thick. A thorough analysis of morphometry of the 98 Geyik cirques, using the revised Automated Cirque Metric Extraction version 2 (ACME2) toolbox, shows that they are relatively small, with limited widths: the median length/width ratio of 1.29 is unusually high. With size, length and width increase faster than depth, demonstrating strong static allometry. Maximum slope averages 59°, minimum 3.3° and axial 25°. A combination of low hypsometric integral, high axial profile closure and high axial height-length integral is proposed as a measure of cirque development.The main summits are on sharp ridges on cirque crests, showing that they have been lowered by glacial erosion (by cirque development). Glaciation was strongly asymmetric, with cirque vector mean aspect between northeast and north-northeast. This shows the dominance of solar radiation effects, with some modification from westerly winds. Glacier palaeo- Equilibrium Line Altitudes (pELAs) rise northeastwards and cirque floor minimum altitudes (CFAs) rise toward east-northeast, both showing the importance of moist air from the Mediterranean, 38–55 km to the southwest. pELA averages 2208 m above sea level (a.s.l.) (2277 m area-weighted); CFA averages 2234 m. CFA varies mainly with summit altitudes; where related palaeoglaciers are short CFA is somewhat below pELA, but for longer ones it is above. The most likely palaeoclimate to form these glaciers involves a precipitation increase of 53–72 % with a temperature fall of 8 °C compared with present-day. The cirques formed under similar or less severe conditions.

Development and persistence of hazardous atmospheres in a glaciovolcanic cave system—Mount Rainier, Washington, USA

Glaciovolcanic cave systems, including fumarolic ice caves, can present variable atmospheric hazards. The twin summit craters of Mount Rainier, Washington, USA, host the largest fumarolic ice cave system in the world. The proximity of fumarole emissions in these caves to thousands of mountaineers each year can be hazardous. Herein we present the first assessment and mapping of the atmospheric hazards in the Mount Rainier caves along with a discussion on the microclimates involved in hazard formation and persistence. Our results are compared to applicable life-safety standards for gas exposure in ambient air. We also describe unique usage of Self-Contained Breathing Apparatus (SCBA) at high altitude. In both craters, subglacial CO2 traps persist in multiple locations due to fumarole output, limited ventilation, and cave morphology. CO2 concentrations, calculated from O2 depletion, reached maximum values of 10.3 % and 24.8 % in the East and West Crater Caves, respectively. The subglacial CO2 lake in West Crater Cave was persistent, with atmospheric pressure as the main factor influencing CO2 concentrations. O2 displacement exacerbated by low O2 partial pressure at the high summit altitude revealed additional cave passages that can be of immediate danger to life and health (IDLH), with O2 partial pressures as low as 68.3 mmHg. Planning for volcanic research or rescue in or around similar cave systems can be assisted by considering the implications of atmospheric hazards. These findings highlight the formation mechanisms of hazardous atmospheres, exploration challenges, the need for mountaineering and public awareness, and the broader implications to volcanic hazard assessment and research in these environments.

Ground thermal regimes and implications for permafrost distribution on Kilimanjaro, Tanzania

ABSTRACT Tropical mountain permafrost has a unique thermal regime due to ground surface exposure to strong solar radiation. The intensity of the surface offset resulting from snow cover also strongly affects the absence or presence of permafrost. Latent heat transfer and reflected solar radiation (higher albedo) that occur during the snow-covered season contribute to a positive feedback that cools the ground. Eleven ground temperature monitoring sites were established on the mountain at 2,780 to 5,820 m.a.s.l. The geothermal heat flow is locally high in the caldera of this volcano, as shown by borehole temperature data. Permafrost is located near the only glacier entirely within the caldera (Furtwängler). These three-year continuous records of ground temperature data encompass years of high and low snow cover. Our results show that the current lower boundary of permafrost is slightly above summit altitude and relict permafrost is present due to the influence of saturated sand on latent heat transfer. Permafrost tends to be lost more rapidly during drought years. The remaining permafrost seems likely to disappear in the future. The presence of permafrost and its thermal resistance depends on the ice content of caldera sand and the duration of snow cover.

Glaciers, rock avalanches and the ‘buzzsaw’ in cirque development: Why mountain cirques are of mainly glacial origin

AbstractIt has been proposed that most cirques are source‐area depressions of large, deep‐seated rock‐slope failures. Yet the close relation between cirques and climate is convincing evidence of the dominance of glacial erosion, rather than rock‐slope failure, in mountain cirque development and distribution. Cirque floor altitudes have a lower limit that varies with snowfall by 1000 m or more between windward and leeward sides of mountain systems. Glaciation levels and equilibrium line altitudes implied by cirques vary in parallel with those for modern glaciers. Cirques are often found mainly on the poleward or leeward slopes of individual mountain ranges, as are modern small glaciers (because of solar radiation and wind effects on ablation and accumulation).Most rock‐slope failures (RSFs: rock slides, rock avalanches and gravitational deformations) do not involve the deep‐seated rotational movement that would produce a cirque form. Although some deep‐seated RSFs with arcuate head scars may be confused with cirques, identification as a glacial cirque is more confident as the floor is longer, wider and more gently sloping. Some scars from major RSFs may resemble poor or moderately developed cirques, but tend to have steeper floors, to be more scattered and closely related to geology, whereas glacial cirques develop on all rock types. Deep‐seated RSFs high on slopes can be associated with seismic shaking, but cirques develop without relation to seismicity. Degree of cirque development can be related to duration of exposure to glaciation. Often RSFs are found adjacent to cirques, or in glacial transfluences; only a proportion are well situated to develop into glacial cirques. Valley‐head cirques are continued down‐valley by glacial troughs. The ‘overdeepening’ (rock basins with reversed slopes) found in a large minority of cirques is not due to rock avalanching, fluvial or periglacial erosion.The RSF proposal should therefore be rejected in favour of the traditional glacial explanation, without any nivation stage being necessary. Rock‐slope failure is one of several possible ways of initiating hollows for glacier accumulation, as well as an ancillary process of cirque extension or widening through collapse of glacially oversteepened slopes.Headward extension of adjacent cirques on a ridge leads to displacement of the divide, sometimes by 2 km or more, lowering ridge and summit altitudes and producing the ‘glacial buzzsaw’ effect. Where a relatively lower snowline has led to cirque erosion on all sides of a mountain, cirque intersection lowers summits further. The buzzsaw hypothesis is not applicable, however, where remnants of a preglacial summit surface survive. © 2020 John Wiley & Sons, Ltd.

Analysis of the glacial geomorphological characteristics of the last glacial in the Tianger area, Tien Shan, and their paleoclimate implications

AbstractThe Tianger area in the Tien Shan preserves many glacial landforms to which several methods of estimating ancient equilibrium-line altitudes (ELAs) can be applied. Thus it provides the opportunity to compare different methods and evaluate the correlation between the methods and their errors. This comparison provides guidance in the application of these methods in other mid-latitude alpine glaciated areas. In this paper we calculate characteristic ratios relating to the ELAs, including accumulation–area ratio (AAR), toe–headwall altitude ratio (THAR), terminus–summit altitude method (TSAM) and Höfer value, and their correlations with each other and the geomorphological characteristics. The AAR of a glacier is small when the slope of the bedrock beneath it is small and the area is large, and the AAR of a glacier with such characteristics is better correlated with its THAR, TSAM and Höfer value. Paleoclimate information derived from these characteristic ratios relating to ELAs is discussed. The glaciers and the glacial climate of the early and middle stage of the last glacial are more continental than those of the Last Glacial Maximum (LGM). Compared with those of the LGM on the Qinghai–Tibetan Plateau and surrounding mountains, the ELA characteristics of the early and middle stage of the last glacial in the Tianger area show more continental features.

Influence of a glacial buzzsaw on the height and morphology of the Cascade Range in central Washington State, USA

Analysis of climatic and topographic evidence from the Cascade Range of Washington State indicates that glacial erosion limits the height and controls the morphology of this range. Glacial erosion linked to long-term spatial gradients in the ELA created a tilted, planar zone of 373 cirques across the central part of the range; peaks and ridges now rise ≤600 m above this zone. Hypsometric analysis of the region shows that the proportion of land area above the cirques drops sharply, and mean slopes >30° indicate that the areas above the cirques may be at or near threshold steepness. The mean plus 1σ relief of individual cirque basins (570 m) corresponds to the ∼600-m envelope above which peaks rarely rise. The summit altitudes are set by a combination of higher rates of glacial and paraglacial erosion above the ELA and enhanced hillslope processes due to the creation of steep topography. On the high-precipitation western flank of the Cascades, the dominance of glacial and hillslope erosion at altitudes at and above the ELA may explain the lack of a correspondence between stream-power erosion models and measured exhumation rates from apatite (U-Th/He) thermochronometry.

Load transmission by elastic, elasto-plastic or fully plastic deformation of rough interface asperities

The normal contact between two nominally flat, parallel rough surfaces is analysed on the microgeometric scale from a theoretical point of view. The microgeometry is described using a probabilistic model based on the quantification of the variability in the summit altitude and the asperity radius. This model takes for its basic data six standardised parameters for roughness and waviness defects measured on both surfaces in contact. For a given separation between two surfaces, this model allows us to determine the number of asperities in contact and their respective indentations. For each asperity in contact, realistic indentation laws are developed taking into account either elastic, elasto-plastic or plastic deformation. The continuous sum of the loads at each asperity gives the global load at the contact and the force transmitted through elastic, elasto-plastic or fully plastic deformed asperities. The theoretical analysis of classical surfaces possessing various mechanical characteristics confirms the combined influence of microgeometry (roughness and waviness parameters) and mechanical characteristics (Young's modulus, Poisson's ratio and yield stress) on load transmission. The association of these parameters into a classical index for plasticity confirms previous predictions. The last necessary parameter is the normal load applied through the contact. This parameter does not appear in previous theories for the plasticity index but can drastically change the degree of plasticity in the contact. The main contribution of our research consists in the quantification of the proportion of plastification in the contact at a given normal load.

Early rocket observations of auroral Bremsstrahlung and its absorption in the mesosphere

In the summer and autumn of 1957 the author and his colleagues at the University of Iowa conducted 10 successful balloon‐launched rocket (rockoon) flights of Geiger‐Mueller tubes during two shipboard expeditions, one to the arctic and the other to the antarctic. Summit altitudes ranged from 77 to 130 km. One flight was conducted in the equatorial zone, six in the northern auroral zone, and three in the southern auroral zone. Detailed results of each flight are presented. Auroral bremsstrahlung was detected on eight of the nine high‐latitude flights. By virtue of physical shielding, the detectors were insensitive to photons of energy E < 8 keV. Hence our derived absolute spectra refer to the high‐energy tail of the auroral electron spectrum and the resulting bremsstrahlung. For the energy range E > 8 keV, we find a typical e‐folding energy E* of about 10 keV for a differential photon number spectrum of the form dn/dE = A exp(−E/E*) with A in units of photons (cm² s keV)−1. Essentially, the same value of E* is obtained by two complementary methods: (1) The dependence of counting rate on atmospheric depth Q and (2) the inverse ratio of counting rates of an “unshielded” tube and one with an added shield. A detailed discussion of the bases for interpretation of the flight data is given in an extended appendix. For a representative set of data (flight 64) we find an omnidirectional flux of downward moving photons of 2.4×104 (cm² s)−1 at Q = 0, the integral of the above spectrum from E = 0 to E = ∞ with the explicit understanding that this result does not include the presumably much greater flux of photons having E < 8 keV and a much steeper spectrum. The corresponding electron number flux striking the top of the atmosphere is 9.3×107 electrons (cm² s)−1 with an e‐folding energy T* = 30 keV. The corresponding energy flux is 4.5 erg (cm² s)−1. Both of the two latter fluxes represent the integral from electron energy T = 0 to T = ∞ of the high‐energy tail of the electron spectrum, again with the explicit understanding that the estimates do not include the steeply rising spectrum for T ≲ 15 keV.

Alexander M. Kellas and the physiological challenge of Mt. Everest.

Alexander M. Kellas (1868-1921) was a British physiologist who made pioneering contributions to the exploration of Everest and to the early physiology of extreme altitudes, but his physiological contributions have been almost completely overlooked. Although he had a full-time faculty position at the Middlesex Hospital Medical School in London, he was able to make eight expeditions to the Himalayas in the first two decades of the century, and by 1919 when the first official expedition to Everest was being planned, he probably knew more about the approaches than anybody else. But his most interesting contributions were made in an unpublished manuscript written in 1920 and entitled "A consideration of the possibility of ascending Mount Everest." In this he discussed the physiology of acclimatization and most of the important variables including the summit altitude and barometric pressure, and the alveolar PO2, arterial oxygen saturation, maximal oxygen consumption, and maximal ascent rate near the summit. On the basis of this extensive analysis, he concluded that "Mount Everest could be ascended by a man of excellent physical and mental constitution in first-rate training, without adventitious aids [supplementary oxygen] if the physical difficulties of the mountain are not too great." Kellas was one of the first physiologists to study extreme altitude, and he deserves to be better known.

Cenozoic thermal evolution and tectonics of the Coast Mountains of British Columbia: 1. Fission track dating, apparent uplift rates, and patterns of uplift

The high relief of the Coast Mountains of British Columbia has been produced in part by rapid late Neogene uplift. The relationship of this uplift to the presently diverse and complex plate tectonic regime off the west coast of British Columbia, however, is not clear‐cut. To study this problem, the areal patterns, rates, and total amounts of Cenozoic uplift from 50° to 55°N have been determined by using fission track dating of zircon and apatite separated from rocks collected at high and low altitudes along several traverses through the mountains. Accepting closure temperatures of 105°C ± 10°C and 175°C ± 20°C for apatite and zircon, respectively, and a likely closure temperature difference between zircon and apatite of 70° ± 15°C, paleogeothermal gradients have been measured at Kemano ( °C/km 35 Ma ago) and near Ocean Falls‐King Island ( °C/km 20 Ma ago). Subcrustal heat flow is suggested to have significantly increased in the late Neogene near King Island. Uplift rates in the axial part of the northern (52°–55°N) Coast Mountains were 0.1–0.2 km/Ma from 25 to 15 Ma ago; this uplift was temporally and tectonically related to part of the subsidence in the adjacent Queen Charlotte basin. Uplift rates increased somewhat in the Late Miocene to about 0.4 km/Ma, probably due to passage of the Anahim “hot spot” beneath the area. Late Miocene‐Recent erosion in the north (52°–55°N) has reduced summit altitudes and been more extensive than farther south. Despite this, relicts of Miocene river valleys and topography are still locally preserved, partly beneath 7–10 Ma basalts. The area of the present southern (50° to 52°N) Coast Mountains was near sea level and experienced very low uplift rates (<0.1 km/Ma) throughout the middle Cenozoic (30–10 Ma), despite its more active volcanism. Late Miocene basaltic lavas that were erupted onto a mature erosion surface near Taseko Lakes were elevated and warped by rapid Pliocene‐Pleistocene uplift (>0.5 km/Ma) of the southern Coast Mountains. The profile of this uplift was broadly plateaulike, and this uplift led to the inversion of the Miocene coastal topography. Middle Cenozoic uplift from 52° to 55°N was probably the result of denudation and diminishing uplift after the terminal Paleocene‐Eocene orogenic episode which grossly thickened the crust. This middle Cenozoic erosion resulted in the restoration of a normal crustal thickness. Late Neogene uplift in the Coast Mountains was the result of thermal expansion in the mantle caused by a mantle hot spot near 53°N and changes in the geometry of the subducted slab farther south.

Winds at an Interior Alaska Summit

One purpose of this study was to compare anemometer-based average wind speeds at a well-exposed interior Alaskan summit with those deduced from local rawinsonde data at the same summit altitude. The second purpose was to evaluate the wind power potential of the site investigated. Winds measured by an anemometer for two years (1979–81) at Murphy Dome Air Force Station, Alaska, 893 m above sea level, gave an annual scalar wind speed V̄n of 6.33 m s−1 (14.2 mph) at 13.7 m (45 ft) above ground. The measured seasonal average speeds of 7.48 (winter), 5.70 (spring), 5.98 (summer) and 6.14 m s−1 (autumn) agree well with estimates based on free-stream (rawinsonde) winds V̄f from long-term (1948–70) data at the same altitude. The latter came from the vicinity of the Fairbanks International Airport, 27 km southeast of Murphy Dome. The ratios V̄n/V̄f were 1.1 (winter), 0.99 (spring), 1.1 (summer) and 0.97 (autumn). The wind power potential of the station is good to excellent throughout the year, in sharp contrast to the poor potential of Fairbanks.

The Lowland Floral Element on the Summit of Cerro Guaiquinima and Other Cerros of the Guayana Highland of Venezuela

Cerro Guaiquinima is one of the largest of the sandstone table mountains (tepuis) of the Venezuelan Guayana. The relatively abundant vegeta- tional cover with an especially high percentage of tall forest, together with a rather level topography and deficiency of rock outcrops are outstanding features. The summit attains an altitude of 1680 m above sea level, but in some parts drops to 700 m, a record low level for the summit altitudes of the major table mountains. The phanerogamic flora encountered on the summit consists of a mixture both of elements characteristic of and endemic to the summits of the sandstone table mountains as well as a considerable proportion (21.6%) of the flora of low altitudes. The relatively low percentage (9.5%) of the endemic phanerogamic flora of the summit provides further evidence that the summit floras of these sandstone mountains often harbours less than 50% of the total flora. Vertical upward movement of the flora from the lowlands is postulated on the basis of either (1) present-day dispersal along available migration routes by means of the low passes extending to the summit from the Rio Carapo and other affluents tributary to the Rio Paragua on the south and west flanks of Cerro Guaiquinima, or (2) upward migration during one of the warmer interglacial stages of the Pleistocene Epoch, when warmer and/or more humid climate pre- vailed. The relatively high percentage of the lowland flora encountered on the summit supports the view that a considerable vertical movement is involved in this dispersal, and negates the contrary view that no significant dispersal move- ments have occurred between species on the summits and those in the contiguous lower levels of the mountains.

Drainage Density, Length Ratios, and Lithology in a Glaciated Area of Southern Connecticut

Twenty-five third order basins in the Mount Carmel quadrangle, Connecticut, were analyzed morphometrically with emphasis on drainage density and length ratios. Drainage density and maximum summit altitude are adjusted to lithology, indicating that the landscape is in dynamic equilibrium, despite the influence of glaciation and possible past erosion cycles. Total length ratio correlates with lithology, but mean length ratio does not. The latter is a function of the bifurcation ratio, and hence has an important environmentally independent stochastic component.

Glaciation of Shickshock Mountains, Gaspe Peninsula

Research Article| August 01, 1942 Glaciation of Shickshock Mountains, Gaspe Peninsula RICHARD FOSTER FLINT; RICHARD FOSTER FLINT Search for other works by this author on: GSW Google Scholar MAX DEMOREST; MAX DEMOREST Search for other works by this author on: GSW Google Scholar A. L. WASHBURN A. L. WASHBURN Search for other works by this author on: GSW Google Scholar GSA Bulletin (1942) 53 (8): 1211–1230. https://doi.org/10.1130/GSAB-53-1211 Article history received: 03 Mar 1942 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation RICHARD FOSTER FLINT, MAX DEMOREST, A. L. WASHBURN; Glaciation of Shickshock Mountains, Gaspe Peninsula. GSA Bulletin 1942;; 53 (8): 1211–1230. doi: https://doi.org/10.1130/GSAB-53-1211 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Shickshock Mountains constitute one of the highland areas that have been considered by Coleman on geologic evidence, and by Fernald on botanical and geologic evidence, to have been nunataks during the maximum of Wisconsin glaciation.Recent field studies have been made on the two highest parts of the Shickshocks—the broad plateaulike masses known as Mount Albert (summit altitude 3775 feet) and Tabletop Mountain (4230 feet). Glacial erratics possibly derived from pre-Cambrian rocks from north of the St. Lawrence were found as high as 3760 feet on Mount Albert. On Tabletop Mountain, striated surfaces were found as high as 3500 feet, and glacial erratics (of local origin) as high as 3700 to 3800 feet. Detailed search failed to produce any direct evidence of glaciation through the highest 400–500 feet. Throughout this distance evidences of any possible glaciated surfaces are obscured by mantles of locally derived felsenmeer that presumably originated in postglacial time. In addition, the composition of the bedrock is so heterogeneous that several types of erratic stones might be present without having been recognized. These circumstances do not demonstrate glaciation of the highest parts of Tabletop Mountain; yet there is no geologic evidence inconsistent with the possibility that the entire Shickshock highland was overtopped by Wisconsin ice. No geologic evidence was found, suggesting that any portion of the area existed as a nunatak during the Wisconsin maximum.During the waning stages of glaciation, and possibly earlier, Tabletop was the site of radial outflow from a local ice cap. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The Accordance of Summit Levels among Alpine Mountains: the Fact and Its Significance

THE STATEMENT OF SUMMIT-LEVEL ACCORDANCE. THE VARIOUS EXPLANATIONS OF ACCORDANCE. I. Explanations by Inheritauce. I. The peneplain theory. 2. Hypothesis of original rough accordance of summit levels, due to isostatic adjustment. 3. Hypothesis of original rough accordance, due to differential erosion during the period of alpine plication. 4. Conclusion. The Composite Explanation. II. The Spontaneous Development oj Summit-Level Accordance. I. Spontaneous development by isostatic adjustment. 2. Metamorphism and igneous intrusion in relation to the degradation of mountains. 3. The influence of local glaciation on summit altitudes. 4. The influence of the forest cap on summit altitudes. 5. Accordance through river-spacing and gradation of slopes. GENERAL CONCLUSION AND SUMMARY.