Half Dome Research Articles

Reducing Rockfall Risk in Yosemite National Park

Yosemite National Park preserves some of the world's most spectacular geological scenery, including icons such as Half Dome and El Capitan. The glacially sculpted granite walls of Yosemite Valley attract 4 million visitors a year, but rockfalls from these cliffs pose substantial hazards (Figure 1).

A visitor use monitoring approach on the Half Dome cables to reduce crowding and inform park planning decisions in Yosemite National Park

Regulating visitor access, in the form of user limits, on public lands is a contentious issue. Although visitor use limits have been instituted to manage a variety of recreation activities in national parks there is little research that has successfully demonstrated relationships between visitor use levels and evaluative conditions (e.g. visitor perceptions of crowding). The lack of empirical understanding of relationships between use levels and evaluative conditions brings into question the efficacy of use limits to achieve management objectives. This paper describes a research and monitoring program that identifies clear management objectives and definitive visitor use pattern relationships to manage visitor use on Half Dome in Yosemite National Park to inform the development of the Half Dome Trail Stewardship Plan that established a permit system to limit visitor use on and around Half Dome. Automated visitor counters were used to collect trail use level data and photographic documentation was used to collect people-at-one-time (PAOT) data on the cable route. Regression analyses yielded strong relationships between these data and show that 400 people per day significantly reduces crowded conditions and preserves unimpeded travel on the Half Dome cables. The approach and results developed in this project provide a basis for future monitoring to promote adaptive management of visitor use on Half Dome in order to ensure that management objectives related to quality visitor experiences and safety are met.

Transport and thermodynamic properties of (Ca1−xLax)10(Pt3As8)(Fe2As2)5superconductors

Single crystals of (Ca${}_{1\ensuremath{-}x}$La${}_{x}$)${}_{10}$(Pt${}_{3}$As${}_{8}$)(Fe${}_{2}$As${}_{2}$)${}_{5}$ ($x=0$--0.182) superconductors have been grown and characterized by x-ray, microprobe, transport, and thermodynamic measurements. Features in the magnetic susceptibility, specific heat, and two kinks in the derivative of the electrical resistivity around 100 K in the $x=0$ compound support the existence of decoupled structural and magnetic phase transitions. With La doping, the structural/magnetic phase transitions are suppressed and a half dome of superconductivity with a maximal ${T}_{c}$ around 26 K is observed in the temperature-concentration phase diagram.

Reducing Donor Site Morbidity When Reconstructing the Nipple Using a Composite Nipple Graft

BackgroundNumerous procedures are available for nipple reconstruction without a single gold standard. This study presents a method for reducing donor-site morbidity in nipple reconstruction using a composite nipple graft after transverse rectus abdominis musculocutaneous flap breast reconstruction.MethodsThirty-five patients who underwent nipple reconstruction using a composite nipple graft technique between July of 2001 and December of 2009 were enrolled in this study. To reduce the donor site morbidity, the superior or superior-medial half dome harvesting technique was applied preserving the lateral cutaneous branch of the fourth intercostal nerves. The patients were asked to complete a previously validated survey to rate the color and projection of both nipples, along with the sensation and contractility of the donor nipple; and whether, in retrospect, they would undergo the procedure again. To compare projection, we performed a retrospective chart review of all the identifiable patients who underwent nipple reconstruction using the modified top hat flap technique by the same surgeon and during the same period.ResultsThirty-five patients were identified who underwent nipple reconstruction using a composite nipple graft. Of those, 29 patients (82.9%) responded to the survey. Overall, we received favorable responses to the donor site morbidity. Projection at postoperative 6 months and 1 year was compared with the immediate postoperative results, as well as with the results of nipples reconstructed using the modified top hat flap.ConclusionsThe technique used to harvest donor tissue is important. Preserving innervation of the nipple while harvesting can reduce donor site morbidity.

Painting Yosemite Valley: A Case Study of Rock Coatings Encountered at Half Dome

No prior research has documented the different types of rock coatings in Yosemite Valley, despite the evident black streaks down Yosemite Falls, the light granitic rock exposed by recent rock falls contrasting with dark rock coatings, and the millions of visitors who have photographed the coated rocks of Yosemite. This paper identifies the types of rock coatings found on Half Dome, in Yosemite Valley, assesses the hypothesis that the rock coatings of Yosemite are consistent with the landscape geochemical model of rock coating formation, and considers the relevance of equifinality. Eight types of rock coatings were identified: case-hardened surfaces, heavy metal skins, iron films, lithobiontic coatings, oxalate crusts, manganiferous rock varnish, silica glaze, and anthropogenic pigments. The landscape geochemical model of rock coating formation and the concept of equifinality both proved useful in this investigation.

Explaining sheeting joints on Yosemite's Half Dome

Explaining sheeting joints on Yosemite's Half Dome

Is chemical zonation in plutonic rocks driven by changes in source magma composition or shallow-crustal differentiation?

Lithologic and magnetic-susceptibility mapping of the western Half Dome Granodiorite of the Tuolumne Intrusive Suite of California reveals seven km-scale lithologic cycles, each of which is bounded by a sharp west-dipping contact that is subparallel to the external contact of the pluton. Crosscutting relations indicate that the cycles become younger to the east. Each cycle is inferred to have been a zone of partial melt in which an eastern melt-depleted base grades westward to a melt-rich top now preserved as a leucocratic facies of the Half Dome Granodiorite. Sharp contacts between cycles may record freezing episodes when the rate of heat input into the growing pluton dropped below that required to maintain interstitial melt. Thus, the interstitial melt zone migrated with time and its size at any given time need not have differed greatly from the ∼1 km thickness of the cycles. Cycles occur on the outer, older margins of the suite, and disappear toward the interior, younger intrusions. Inward disappearance of cycles likely reflects thermal maturation of the system such that melt was continuously present until the final migration of the solidus through the intrusive suite. Although the cycles span the compositional range from granodiorite to leucogranite, trace-element trends preserved in the cycles differ dramatically from those of both the Tuolumne Intrusive Suite and other Cretaceous zoned plutons of the eastern Sierra Nevada batholith. We suggest that (1) the compositional variations of the intrusive suite and the batholith reflect a signal from the source of the magmas, and (2) the geochemistry within the km-scale cycles reflects in situ crystal/liquid separation.

Fractures on curved surfaces: A classic problem solved

Sheeting joints—large fractures parallel to a curved rock surface—are common in many locations on Earth, such as the iconic Half Dome in Yosemite National Park in California. Explaining how these fractures form has been a classic unsolved problem in geology. Martel solved the problem by reformulating the static equilibrium equations in a curvilinear reference frame. His analysis shows that compression along a curved surface can induce tension perpendicular to the surface, which can cause subsurface cracks to open. He found that the curvature of a rock surface plays a key role in the formation of fractures.

The Mammoth Peak sheeted complex, Tuolumne batholith, Sierra Nevada, California: a record of initial growth or late thermal contraction in a magma chamber?

The Mammoth Peak sheeted intrusive complex formed in the interior of a ~7–10 km deep magma chamber, specifically in the Half Dome granodiorite of the Tuolumne batholith, central Sierra Nevada, CA (USA). The sheets consist of fractionated melts with accumulated hornblende, biotite, magnetite, titanite, apatite, and zircon. The accumulation, especially of titanite, had a profound effect on minor and trace elements (Nb, Ta, Ti, REE, U, Th, P, Zr, Hf, etc.), increasing their contents up to five to six times. Our thermal–mechanical modeling using the finite element method shows that cooling-generated tensile stresses resulted in the inward propagation of two perpendicular sets of dilational cracks in the host granodiorite. We interpret the sheeted complex to have formed by a crack-seal mechanism in a high strength, crystal-rich mush, whereby outward younging pulses of fractionated magma were injected into these syn-magmatic cracks at the margin of an active magma chamber. Thermal–mechanical instabilities developed after the assembly of the sheeted complex, which was then overprinted by late ~NW–SE magmatic foliation. This case example provides a cautionary note regarding the interpretation that sheeted zones in large granitoid plutons imply a diking mechanism of growth because the sheeted/dike complexes in plutons (1) may display inverse growth directions from the growth of the overall intrusive sequence; (2) need not record initial chamber construction and instead may reflect late pulsing of magma within an already constructed magma chamber; (3) have an overprinting magmatic fabric indicating the continued presence of melt after construction of sheeted complexes and thus a prolonged thermal history as compared to dikes; and (4) because the scale of the observed sheeted complexes may be small (<1%) in comparison to large homogenous parts of plutons, in which there is no evidence for sheeting or diking. Thus, where extensive dike complexes in plutons are absent, such as in much of the Tuolumne batholith, the application of an incremental diking model to explain chamber construction is at best speculative.

Causes of compositional diversity in a lobe of the Half Dome granodiorite, Tuolumne Batholith, Central Sierra Nevada, California

ABSTRACTThe causes of compositional diversity in the Tuolumne Batholith, whether source heterogeneity, magma mixing, or fractional crystallisation, is a matter of longstanding debate. This paper presents data from detailed mapping and a microstructural and major element, trace element and isotopic study of an elongate lobe of the Half Dome granodiorite that protrudes from the southern end of the batholith. The lobe is normally zoned from quartz diorite along the outer margin to high-silica leucogranite in the core. Contacts are steep and gradational, except for the central leucogranite contact, which is locally sharp: magmatic fabrics overprint contacts. A striking feature of the lobe is the 18 wt SiO2 range comparable to that observed for the entire Tuolumne Batholith. Feldspar-compatible elements (Sr and Ba) decrease towards the centre, while Rb increases. Light and middle REEs show a smooth decrease towards the centre of the lobe. Calculated initial isotopic ratios of 87Sr/86Sr(i) and εNd(t) have identical values within error across the lobe, except in the central leucogranite, the most silica rich phase, which shows a slightly more crustal signature. Field, structural, geochemical and isotopic data suggest that fractionation was the dominant process causing compositional variation in this lobe. It is envisioned that this fractionation/crystal sorting occurred in a vertically flowing and evolving magma column with the present map pattern representing a cross-section of this column. Thus the areal extent of the lobe represents a minimum size of interconnected melt at the emplacement level of the Tuolumne Batholith and, given its marginal position, limited width and proximity to colder host rocks, implies that fractionation in larger chambers likely occurred in the main Tuolumne Batholith magma chamber(s).

Formation of Igneous Layering in Granodiorite by Gravity Flow: a Field, Microstructure and Geochemical Study of the Tuolumne Intrusive Suite at Sawmill Canyon, California

Layered granites and granodiorites occur in many plutons. They occur, together with non-layered granodiorites, at the margin of the Tuolumne Intrusive Suite, one of the largest late Cretaceous intrusions in the Sierra Nevada. Results from field observations, quantitative microstructural analysis and whole-rock compositions from the non-layered Kuna Crest, Half Dome and Cathedral Peak granodiorites and layered granodiorites from the Sawmill Canyon area are compared to determine which processes contributed to the formation of the layering. The non-layered granodiorites have foliated but homogeneous microstructures, which are attributed to the orientation of crystals with high aspect ratios when the magma flowed before solidification; their compositions are consistent with magma mixing and fractional crystallization. The microstructure in the layered granodiorite is heterogeneous, and shows normal gradation of the dense, primocryst minerals magnetite, hornblende and titanite at the base, and inverse size gradation with large crystals of the less dense primocryst phases plagioclase and biotite at the top, and a systematic change in the preferred orientation of minerals from base to top. Macroscopic structures in the layers indicate erosion and the action of traction currents when the layers formed, and the sinking of the dense minerals and rise of interstitial melt immediately afterwards. The layered rocks have similar grain size and mineral compositions to the non-layered granodiorites, and thus could be derived from the same magmas as the Kuna Crest, Half Dome and Cathedral Peak non-layered granodiorites. The major and trace element variations in the layered rocks are very different from those in the non-layered rocks and indicate a strong segregation of crystals during formation of the layers. However, the separation process did not fractionate the main rare earth element-bearing phases from one another. The macrostructure and microstructural features in the layers resemble those from hyper-concentrated sediment gravity flows. The layering is interpreted to have formed from gravity flows of melt and crystals initiated by syn-magmatic tectonic deformation and seismic shaking. Two types of layering are identified; one, called normal layering, represents material derived from a single granodiorite magma and deposited from a relatively low-energy gravity flow, whereas the other, called melanocratic layering, incorporated mafic minerals eroded from the substrate, had the felsic tops of layers eroded off by subsequent flows, incorporated crystals from more than one magma source and formed from gravity flows that had higher energy.

Growth of complex sheeted zones during recycling of older magmatic units into younger: Sawmill Canyon area, Tuolumne batholith, Sierra Nevada, California

In Sawmill Canyon, located near the eastern margin of the Tuolumne batholith, central Sierra Nevada, California, a series of petrologically and structurally complex, magmatic sheeted zones intrude older granodioritic units (Kuna Crest and equigranular Half Dome) and in one case truncate these units along a sharp contact. These sheeted zones (a) consist of numerous batches of (now frozen) magma, (b) display clear outward growth directions, (c) were actively deforming during and after emplacement resulting in magmatic folds, faults and multiple magmatic mineral fabrics, and (d) are the location of numerous, but localized magma flow structures (schlieren-bounded tubes, troughs, megacryst-rich pipes) and instabilities (load casts, flame structures, slumps, diapirs, ridge and pillar structures). Geochemical data indicate that the sheeted zones largely consist of magmas derived from the Half Dome granodiorite with some late Cathedral Peak granodiorite pulses, and with fractionation and flow sorting forming widespread layering in the above structures. We interpret these sheeted zones to record the pulsing of magma during propagation and expansion of opening-mode (Mode I), submagmatic fractures at the margins of large blocks of older, fairly solidified magmatic pulses that were subsequently removed from the present crustal level. Elsewhere in the Tuolumne batholith we see similar features suggesting that a “recycling” process, i.e., the breaking off of older parts of the magma chamber and incorporation into younger intrusive units, occurred in this batholith. This recycling removed a significant portion of older units and resulted in the formation of sheeted zones and local instabilities in this batholith. Finally this recycling is one process responsible for transfer of zircon crystals between units and for obscuring whole-rock geochemical signatures.

Long-term geochemical variability of the Late Cretaceous Tuolumne Intrusive Suite, central Sierra Nevada, California

Abstract This study investigates the internal anatomy and petrogenesis of the Tuolumne Intrusive Suite (TIS), which comprises metaluminous, high-potassium, calc-alkaline granitoids typical of the Sierra Nevada batholith. Although the TIS has often been cited as an example of a large magma chamber that cooled and fractionated from the margins inward, its geochemistry is inconsistent with closed-system fractionation. Most major elements are highly correlated with SiO 2 , but the scattered nature of trace elements and variations of initial Sr and Nd isotopic ratios indicate that fractional crystallization is not the predominant process responsible for its chemical evolution. Isotopic data suggest mixing between melts of mantle-like rocks and a granitic melt similar in composition to the highest-silica TIS unit. Monte Carlo models of magma mixing confirm that such processes can reproduce the observed variations in major elements, trace elements and isotopic ratios. Thermobarometry suggests emplacement at depths near 6 km and crystallization temperatures ranging from 660 to 750 °C. Feldspars, hornblende, biotite and magnetite exhibit evidence of extensive low-temperature subsolidus exsolution. The TIS as a whole trends toward more evolved isotopic compositions and younger U–Pb zircon ages passing inward. This pattern indicates a general increase in the proportion of felsic, crustally derived melt in the mixing process, which may have resulted from net accumulation of heat added to the lower crust by intrusion of mantle-derived mafic magma. However, the bulk geochemical and isotopic compositions of the equigranular Half Dome Granodiorite, the porphyritic Half Dome Granodiorite and the Cathedral Peak Granodiorite overlap one another and the contacts between them are commonly gradational. We interpret these map units to represent a single petrological continuum rather than distinct intrusive phases. The textural differences that define the units probably reflect thermal evolution of the system rather than distinct intrusive events.

Half Dome from Olmsted Point, Yosemite National Park, Yosemite, California

Half Dome from Olmsted Point, Yosemite National Park, Yosemite, California

Rethinking the emplacement and evolution of zoned plutons: Geochronologic evidence for incremental assembly of the Tuolumne Intrusive Suite, California

New U-Pb geochronologic data indicate that the Tuolumne Intrusive Suite, California, was assembled over a period of at least 10 m.y. between 95 and 85 Ma, and that the Half Dome Granodiorite intruded over a period approaching 4 m.y. Simple thermal considerations preclude the possibility that a magma chamber the size of the Half Dome pluton could have existed as a liquid at shallow crustal depths for that long. Rather, field evidence for sheeting along the margins of the suite, the range of ages, and the regular decrease of ages toward the center of the suite and within individual plutons suggest incremental assembly. Geochronologic evidence for incremental assembly is consistent with the failure of geophysical methods to detect large magma chambers with more than ∼20% melt, even in active volcanic areas. Because it is unlikely that the individual plutons composing the Tuolumne ever coexisted as liquid-rich magmas, the chemical evolution of the suite cannot be the result of simple fractionation and/or mixing between exposed units, but instead must reflect processes occurring during magma generation.

An analysis of absorbed radiation by domed and vaulted roofs as compared with flat roofs

Domed or vaulted roofs have been extensively used in buildings throughout the Middle East and other hot arid regions. Many studies have focused on climate-related considerations, but very little quantitative research exists in the literature. In this study, an attempt was made to calculate the insolation absorbed by these roofs, as compared with flat roofs, based on angular dependence of absorptance and solar geometry. Results showed that a domed or vaulted roof will absorb more solar radiation than its corresponding flat roof. The ratios K b, K tot increase with the increase of the half dome or vault angle but are insignificantly affected by climate characteristics and latitude of the location. It was also seen that a south–north facing vaulted roof both reduces the solar heat gain of buildings in summer months and increases solar heat gain in winter months compared to one which faces east–west; the greater the proportion of area exposed to the sun is, the smaller the amount of beam radiation that will be absorbed by a curved roof. Furthermore, results showed that even if absorptance is assumed to be constant this would affect total solar heat gain of the roofs studied by less than 4%.

Morphologies of rocks within and near the Rock Garden at the Mars Pathfinder landing site

This paper considers the morphology of several rocks and rock fragments within and near the Rock Garden at the Mars Pathfinder landing site. We have analyzed stereo images taken both by the lander IMP camera and by the rover forward cameras. The rocks were found to differ in their roundness/angularity and in their densities of millimeter‐to‐centimter‐sized pits and flute‐like features on the rock facets. No correlation between rock roundness and the degree of rock pitting was found, indicating that rounding and pitting formed by different processes. Pits are either gas bubbles (implying the rocks are volcanic), or resulted from eolian abrasion/deflation (putting no constraints on the nature of the rocks), or both. If pits are of eolian origin, variations in the density of pits on different rocks imply that either the rock surfaces have been exposed for different times or the susceptibility of different rocks to pitting varies significantly from rock to rock, implying differences in composition and/or lithology. The densities of pits and flutes on the rocks show anti‐correlation. This may be connected to their formation but probably is mostly related to issues of observation and definition of what is a pit and what is a flute. Flute‐like features may be a result of eolian abrasion, but in this case, the spatial closeness of fluted rocks and those having delicately pitted textures requires explanation. Other mechanisms producing flute‐like features, such as collisions in the deposit‐forming flows and the breaking of rock in impact cratering, should not be ignored. Our observations agree with the conclusion of Golombek et al. [this issue] that deflational exhumation in this area was minor. The observed, relatively large, rocks typically do not show a concentration of small rock fragments at their feet. This implies diurnal thermal cycles are very ineffective at destructing rocks. The rock, Half Dome, may be a conglomerate (as suggested by Smith et al. [1997a] for this and several other rocks), but this hypothesis remains to be proven. Impact craters of a few meters to a few tens meters in diameter may have played a role in the local geology.

Mechanism of exfoliation joint formation in granitic rocks, Yosemite National Park

Fractographic techniques reveal mechanical aspects of exfoliation in granitic rocks at Yosemite National Park, and electronic surveying provides information on their attitudes and dimensions. In the middle elevations of the cliff of El Capitan, exfoliation consists of early fractures a few meters to tens of meters in size which are fan-shaped. Fans at upper elevations point upwards, whereas fans at lower elevations point downwards parallel to the cliff. The fans interact with each other and merge into composite joints hundreds of meters in size, normal to the minimum compressive principal stress. This polarity indicates exfoliation by longitudinal splitting and buckling. The palaeostress causing the exfoliation on the southwestern side of Half Dome is estimated to range between 0.01 MPa and 0.94 MPa. Differences in fracture paleostresses of joints may be used in comparing their relative propagation velocities. It is suggested that the large exfoliation on the southwestern side of Half Dome had undergone a prolonged sub-critical growth before attaining rapid fracture velocities under post-critical conditions.

航技研の飛行シミュレータ用ハーフドーム表示部の三次元表現

航技研の飛行シミュレータ用ハーフドーム表示部の三次元表現

107 航技研の飛行シミュレータ用ハーフドームとその応用例について

A visual sense is an important information source for aircraft pilots. In a modern flight simulator, the image made by computer graphics is used as a visual information. Several equipment which artificial visual information are used as a flight simulator visual system. First, we present display systems for a flight simulator. Next, the half dome type display system which is installed to the National Aerospace Laboratory is explained. Finally, the evaluation results and its application is described.