Rock Surface Temperature Research Articles

Rock surface temperatures in southern Namibia and implications for thermally-driven physical weathering

Rock surface temperatures in southern Namibia and implications for thermally-driven physical weathering

Endolithic Phototrophs from an Active Geothermal Region in New Zealand

Endolithic photosynthetic communities in geothermal siliceous rocks in the area of Rotorua, New Zealand, were analysed using traditional microbiological and molecular biology techniques. Rock surface temperatures varied between 40°C and 60°C. Major endoliths included cyanobacteria of subsections I, II and V. Few subsection IV organisms were found and subsection III (filamentous, non-heterocystous) cyanobacteria were present only as epiliths or chasmoendoliths. Therefore, the endolithic cyanobacterial communities in these sites resembled assemblages as reported for carbonate rocks in other geothermal regions. Cells of the rhodophyte family Cyanidiaceae were detected within rock at various sites. Some of these phototrophic organisms were associated with mineral (presumably silica) deposits and could be important geological agents in siliceous rock deposition.

Temperature observations in Antarctic tafoni: implications for weathering, biological colonization, and tafoni formation

Tafoni have long been recognized, measured and discussed within the Antarctic context. However, with respect to the formative processes tafoni still remain somewhat of an enigma. In terms of the weathering attributes of tafoni, one problem is the monitoring of environmental conditions without the transducers themselves altering that environment. The application of ultra-small thermocouples provides an avenue for monitoring of rock surface temperatures without influence on the tafoni environment. At an Antarctic site temperatures were measured both inside and outside of a tafone, with data at 20 second intervals. These data show a spatial variability that may help explain tafoni development, at least in terms of weathering. Humidity data indicate that moisture conditions are very low such that water-based weathering processes are temporally and spatially constrained. The presence of several episodes of extreme temperature variations indicates that thermal stress may be an important contributor to weathering here. It is argued that the absence of any endolithic communities (at this site) within the sandstone, in which the tafoni develop, is a reflection of weathering rates that exceed the ability of organisms to invade and colonize the rock. At the present time, weathering appears to be primarily in the form of granular disintegration and flaking.

Surface‐climate attributes at Injisuthi Outpost, Drakensberg, and possible ramifications for weathering

AbstractAerial and sub‐aerial climatic data were collected from a station at 1920 m a.s.l. in the Injisuthi region of the South African Drakensberg. Sensors monitored air temperature, soil surface and rock surface temperature, for two rock types, over the summer and winter of 2001/2002. Rainfall was measured from the summer of 2001 to January 2004. These are the first rock and soil surface‐climate data to be collected for an exposed site at this altitude in the area. Rainfall over the two calendar years 2002 and 2003 was found to be below estimates for the region, but patterns imply numerous rock wetting and drying cycles in summer. At the site, air, rock and soil temperatures differ considerably on a diurnal basis with respect to both absolute temperature and daily ranges. Mean rock daily ranges, as conducive to possible thermal fatigue, are found to be similar in the summer and winter periods. Of the two rock types monitored, the darker coloured basalt attained higher maximum and marginally lower minimum temperatures than the sandstone. Soil frost did not occur at 2·5 cm depth, but rock did reach below −6 °C in winter. Both rock types maintain relatively high rock temperatures in winter (exceeding 25 °C), thus chemical weathering is probably only moisture restricted during this dry period. Findings highlight the importance of directly monitoring rock temperature when attempting to discern the rock weathering environment. Copyright © 2006 John Wiley & Sons, Ltd.

Microclimate and weathering in the central Namib Desert, Namibia

Data on rock surface microclimates at four sites (Kleinberg, Vogelfederberg, Gobabeb, and Ganab) along a transect across the central Namib Desert over a 3-year period have been collected, alongside some shorter term data sets. Rock surface temperature (RST), air temperature, wind, relative humidity, and surface wetness data are presented here. Weathering of exposure blocks of local marble and granite has also been monitored over the 3-year period, with change observed visually and with scanning electron microscopy. Complex temporal patterns of rock temperature fluctuations are observed over the 3 years, although the four sites show very similar overall trends, suggesting spatial homogeneity in the rock surface temperature regime. Relative humidity and surface wetness data show clear differences between the four sites, related to the frequency of fogs. Granite blocks show no visible changes after 2 years of weathering, whereas marble blocks (especially those at Ganab) show SEM evidence of structural weakening after 1 year.

Field Measurements of Rock Surface Temperature in Montane Zone

Field Measurements of Rock Surface Temperature in Montane Zone

THE IMPORTANCE OF A CREVICE ENVIRONMENT TO THE LIMPET HELCION PECTUNCULUS (PATELLIDAE)

Helcion pectunculus has an organized distribution within rock crevices with smaller, younger limpets towards the back of the crevice and larger, older limpets towards the crevice mouth. The crevice refuge provides H. pectunculus with a stable and buffered environment with higher relative humidities and lower rock surface temperatures than adjacent exposed rock surfaces. Limpet body temperatures were significantly lower in crevice refuges compared with limpets on adjacent exposed rock surfaces. Body temperatures never exceeded the rock surface temperatures. It is suggested that this is a result of morphological adaptations such as short spines on the shell and allometric growth (shell increasing in height faster than length). Compared with other South African patellids, less force is required to detach H. pectunculus from the substratum and individuals deprived of a crevice refuge experienced extremely high mortalities, 45% of limpets being lost during the first high tide period.

Experimental investigations into the interactions between moisture, rock surface temperatures and an epilithic lichen cover in the bioprotection of limestone

This paper examines the links between moisture, epilithic lichens, rock surface temperatures and weathering. Field and laboratory experiments were conducted in order to investigate the combined effect of surface wetness and Verrucaria nigrescens (an epilithic lichen) on limestone temperature fluctuations. Exposure blocks with and without a lichen cover were subjected to short-term temperature fluctuations and two types of moisture events: artificial showers ( 8 ml rainfall) and larger storms ( 40 ml rainfall). The experiments showed that larger storms are more likely to dampen temperature fluctuations at the rock surface, especially in the presence of an epilithic lichen cover, providing evidence for a mechanism of bioprotection. The conclusion is that the epilithic lichen retains moisture, which reduces thermal stress in the surface of the limestone.

New insights into rock weathering from high-frequency rock temperature data: an Antarctic study of weathering by thermal stress

A major limitation of many weathering studies has been the acquisition of rock temperature data at insufficiently frequent intervals for the meaningful determination of the rate of change of temperature (Δ T/ t). Equipment and/or logistical constraints frequently facilitate temperature measurement at only hourly intervals or, at best, every 10 min. Such data are not adequate for the determination of Δ T/ t required for the evaluation of the freeze–thaw mechanism or thermal stress fatigue. Recent undertakings at different sites in Antarctica (and at other cold-region locations) provide rock temperature measurements at 1-min intervals, which indicate that the perception of the weathering regime would be very different from that generally assumed from longer-interval geomorphological data. These data clearly show that thermal stress fatigue and thermal shock may be more active components of the Antarctic weathering regime than have generally been recognised; the aridity of the study area limits the role of freeze–thaw weathering. Values of Δ T/ t of ≥2 °C min −1 that suggest thermal stress fatigue/shock is operative were recorded; observations of rock flaking are thought to reflect the impact of thermal stress. Further, the data show that contrary to general perceptions, the southern aspect can, in summer, experience higher rock surface temperatures than the north-facing exposure. An examination of rock fracture patterns found in the field shows great similarity to fracture patterns developed in the laboratory as a direct result of thermal shock. The argument is made that greater cognizance should be given to thermal effects.

Direct observation of frost wedging in alpine bedrock

AbstractWidth and temperature of rock joints were automatically monitored in the Japanese Alps. Three years of monitoring on a sandstone rock face shows two seasonal peaks of joint widening in autumn and spring. The autumn events are associated with short‐term freeze–thaw cycles, and the magnitude of widening reflects the freezing intensity and water availability. The short‐term freezing can produce wedging to a depth of at least 20 cm. The spring events follow a rise in the rock surface temperature to 0 °C beneath the seasonal snowcover, and likely originate from refreezing of meltwater entering the joint. Some of these events contribute to permanent enlargement of the joint. Two other joints on nearby rock faces experience only sporadic widening accompanying freeze–thaw cycles and insignificant permanent enlargement. Observations indicate that no single thermal criterion can explain frost weathering. The temperature range at which wedging occurs varies with the bedrock conditions, water availability and duration of freezing. Copyright © 2001 John Wiley & Sons, Ltd.

Experimental simulation of rapid rock block disintegration by sodium chloride in a foggy coastal desert

An environmental chamber was used to simulate a 24-h cycle of rock surface temperature and relative humidity, a stone pavement with differing levels of sodium chloride content, and differing levels of fog precipitation to assess some of the controls of rock weathering in the vicinity of Swakopmund in the Namib Desert. The rock employed was Cretaceous Chalk. Some treatments were effective at causing disintegration after 76 temperature/humidity cycles and 10 fog cycles. Small amounts of fog moisture (0.5 mm per event) were associated with the greatest amounts of breakdown, whereas the amount of salt in the simulated pavements appeared to be of less significance. The experiment showed that sodium chloride can be an effective agent of weathering in a coastal foggy environment.

Effects of Rock Surface Temperature on Exfoliation, Rock Varnish, and Lichens on a Boulder in the Hunza Valley, Karakoram Mountains, Pakistan

Granodiorite boulders on a moraine around the Batura Glacier in the Karakoram Mountains have exfoliation sheets and rock varnish on the south surface, and lichens and salt efflorescence on the north surface. To elucidate the formative conditions of these surface features, temperatures of a boulder at two points, one each on the north and south surfaces, were measured simultaneously with air temperature at 1-h intervals for 1 yr from July 1994 to July 1995. The annual temperature range of the south surface was 50C higher than that of the north surface. The south surface had diurnal temperature ranges of 30'C with no seasonal change, while the north surface had diurnal ranges of 20OC in summer and 50C in winter. Maximum heating and cooling rates of the south surface were high, being + 12.6 and - 14.5?C h-', while those rates in the north surface were low at +6.5 and -7.70C h-', respectively. These results suggest that the difference in microclimatic conditions have affected the formation of rock surface features; for example, high rates of change in rock temperature on the south surface may produce exfoliation sheets.

Effects of Rock Surface Temperature on Exfoliation, Rock Varnish, and Lichens on a Boulder in the Hunza Valley, Karakoram Mountains, Pakistan

Granodiorite boulders on a moraine around the Batura Glacier in the Karakoram Mountains have exfoliation sheets and rock varnish on the south surface, and lichens and salt efflorescence on the north surface. To elucidate the formative conditions of these surface features, temperatures of a boulder at two points, one each on the north and south surfaces, were measured simultaneously with air temperature at 1-h intervals for 1 yr from July 1994 to July 1995. The annual temperature range of the south surface was 5°C higher than that of the north surface. The south surface had diurnal temperature ranges of 30°C with no seasonal change, while the north surface had diurnal ranges of 20°C in summer and 5°C in winter. Maximum heating and cooling rates of the south surface were high, being +12.6 and −14.5°C h−1, while those rates in the north surface were low at +6.5 and −7.7°C h−1, respectively. These results suggest that the difference in microclimatic conditions have affected the formation of rock surface features; for example, high rates of change in rock temperature on the south surface may produce exfoliation sheets.

Effects of direct and indirect heating on the validity of rock weathering simulation studies and durability tests

Rock surface and subsurface temperature responses in samples exposed to direct heating (insolation) under natural hot desert conditions reveal considerable variability between lithologies related to differences in thermal properties, especially albedo and thermal conductivity. However, when the same samples are heated indirectly by air in an oven-based environmental cabinet, lithological differences in temperature response disappear and all samples attain temperatures similar to the air temperature within the cabinet. Rates and patterns of rock decay produced in such environmental cabinets may not, therefore, reflect those encountered under natural conditions, where breakdown is related to micro-environmental conditions at the rock/air interface and where rock temperature is one of the most important controlling factors. In addition to implications for assessment of weathering effectiveness, use of only indirect forms of heating affects the determination of comparative rock durability because all rock types are cycled through the same temperature regimes. Because temperature exerts such a major control on rock breakdown through its control on physical and chemical weathering processes, all significant factors influencing it must be included in the design of weathering simulations and durability tests.

FIELD EXPERIMENTS ON PHYSICAL WEATHERING AND WIND EROSION IN AN ANTARCTIC COLD DESERT

Field experiments were carried out over a five year period with the aim of understanding contemporary weathering and erosional environments in the Sør Rondane Mountains, an Antarctic cold desert region. These include observations of (1) scaling from rockwalls, (2) disintegration of tuff blocks with or without saline solutions, and (3) abrasion of artificial walls by wind. Monitoring was also made of rock surface temperature and wind speed. Despite frequent temperature oscillations across 0°C, rock scaling due to frost action was generally very slow because of low moisture content in the rockwalls. Exposure to the cold, dry climate led to the rapid disintegration of porous tuff blocks including soluble salts like halite and thenardite. This indicates that rates of weathering are increased greatly with the accumulation of such salts in the bedrock. Although gypsum did not cause any visible damage over four years, its widespread occurrence in heavily damaged rocks demonstrates that increasing gypsum contents may also intensify rock breakdown. The snow-laden katabatic wind resulted in rapid wearing of the windward face of an asbestos board with the peak erosion at 30–40 cm above the ground. Nonetheless, the landforms expected from the unidirectional wind characteristics are by no means common features because of lack of abrasive materials, such as snow and sand particles. These experiments suggest that frost weathering and wind erosion are only locally effective where plenty of moisture or an abrasive material is available, whilst salt weathering and removal of the waste by wind play a major role in constructing erosional landforms over the mountains.

濡れた地下風道における気流温度・湿度の実用的な予測手法とシステム

An approximated solution [Eq.(24)] to estimate rock surface temperature of underground airway with partly wet conditions has been provided. It is much simple and practical compared with previous methods or solutions. The solution is applicable to the range of airflow temperature from 0 to 32° or 10 to 40°(see appendix) and practical ranges of humidity, ventilation time, heat transfer rate, wetness, virgin rock temperature and rock thermal properties. Furthermore, an explicit function for the rock surface temperature is derived, then the rock surface temperature can be calculated by simple procedures without any iterative calculations. The short subroutine program in FORTRAN 77 to calculate the rock surface temperature is shown in the appendix.The estimated value of rock surface temperature have been compared with Amano et al's numerical calculation results using two dimensional finite difference method.Finally, a practical calculation system to predict airflow temperature and humidity along underground airways have been proposed using the practical solution of rock surface temperature. The system can consider the effects of airway inclination and wetness or wet area ratio upon airway surface. The calculation results of temperature and humidity along a single airway shows good agreement with the results of Uchino et al. using finite deference method for analysis of rock temperature distribution and some simulation codes reported by Danko et al.Furthermore, it is pointed out that differences between calculation results of the simulation codes suggested by Danko et al. is probably caused by the difference between wetness and wet area-ratio (see Table 2).The present prediction method for temperature and humidity in underground airways have been successfully applied to a general ventilation simulator named MIVENA run on the Microsoft WindowsTM which has been further developed and released by authors.

The relationship between shade and molluscan grazing in structuring communities on a moderately-exposed tropical rocky shore

The relationship between physical factors (principally temperature) and biological factors (herbivory) in structuring mid and low shore communities were investigated on a moderately-exposed tropical rocky shore. Physical stress, as measured by rock surface temperature and evaporation of distilled water, was greatest higher on the shore as a result of increased exposure time. Exclusion of herbivores (by caging) and alteration of physical factors (by shading) caused little visible change in community structure in the mid shore. There was also no difference in community structure between open rock areas and control treatments for experimental manipulations at either shore level. Chlorophyll levels increased in rock chips from treatments at both shore levels that excluded herbivores, but still allowed access to sunlight, indicating a developing biofilm. In the low shore, however, treatments that provided refuge from herbivores and direct sunlight were colonized by barnacles ( Balanus amphitrite) and an encrusting alga, Hildenbrandia. There appeared to be an interaction between these factors in structuring the community, removal of herbivores allowed the settlement of barnacles which was greatest in shaded treatments. On Hong Kong shores during the summer months biological interactions are important low on the shore in combination with physical factors. In the mid shore, however, physical factors appear the major structuring agent. Community structure on Hong Kong shores is dictated by seasonal variation in physical factors which mediate the effect of biological factors such as herbivory.

Interrelationships between water economy and thermo-regulation in the Canyon tree-frog Hyla arenicolor

Canyon tree-frogs, Hyla arenicolor, are found along permanent waterways, but during daylight hours they bask on vertical rock faces in open sun, about a metre above water line. We examined the thermoregulatory activity of H. arenicolor by measuring body temperatures (Tb) and rates of evaporative water loss (EWL) under field conditions, and EWL under controlled laboratory conditions. Rates of EWL for the northern leopard frog, Rana pipiens, were included for comparison. Around midday in June, average Tb, 30·6 ± 0·2°C, was independent of air temperature, water temperature, and surrounding rock surface temperature. Between dawn and dusk, the EWL of basking frogs averaged 24·8 ± 3·5% of body mass, equivalent to the bladder water reserves, 25·1 ± 1·4% of body mass, of these animals. The average resistance to water loss for H. arenicolor, 14·9 ± 0.3 s/cm, was nearly 7-fold greater than the skin of a typical frog, R. pipiens, 2·2 ± 0.3 s/cm, but only about one-fifteenth the average skin resistance of 'waterproof' frogs. The relatively high skin resistance to EWL is adaptive for the thermoregulatory activity of H. arenicolor; preventing excess heat loss through EWL when ambient temperature (Ta) is less than Tb, but permitting excess heat loss through EWL when Ta exceeds Tb , thereby stabilizing Tb during basking.

Infrared monitoring of volcanoes by satellite

Sensors on future satellite platforms will be used routinely for volcano monitoring, with infrared channels offering the potential to detect and measure temperatures of features such as lava bodies and fumarole fields. This is possible even though the surface temperature distributions associated with such phenomena are typically inhomogeneous at the pixel scale, so long as simplifying assumptions can be made. To test the applicability of the technique, we have carried out field studies of a range of volcanic thermal manifestations using portable infrared thermometers. Rock surface temperatures around fumarolic vents exhibit greater stability with time than those associated with actively degassing lava bodies, but in both cases volcanogenic fumes can significantly attenuate the emitted infrared radiation. The scale of the temporal variability, at a given wavelength, dictates the quantitative value of isolated satellite 'snapshots'. If more spectral channels in the infrared were available on remote sensing platforms then more components of the surface temperature distribution could be extracted from the data. Imaging spectrometry offers the greatest flexibility, although data processing, including correction for atmospheric effects, would present difficulties.

Numerical simulation and field testing of flame-jet thermal spallation drilling—1. Model development

Certain polycrystalline rocks will fracture into thin, disk-like fragments when exposed to rapid surface heating. Some current hard-rock drilling methods using supersonic flame-jets as heat sources exploit this behavior for efficient granite quarrying or blasthole formation. Recent extensions of Weibull's theory of rock failure to quantitatively analyze rock spallation are employed to estimate spall size distributions and rock surface temperatures at the onset of spallation. A numerical drilling simulation code incorporating rock failure criteria and turbulent flow effects is developed to predict spallation rates and hole radii under field-drilling conditions. Because an accurate description of heat transfer through a turbulent wall jet is required, the wall-function method is generalized in a crude way to account for compressible flow past roughened, non-adiabatic rock surfaces.