Trachyandesite of Kennedy Table, its vent complex, and post−9.3 Ma uplift of the central Sierra Nevada: Comment

Hildreth et al. (2021) analyzed a set of table mountains near the San Joaquin River that are capped by a 9.3 Ma trachyandesite lava flow and concluded that, since the deposition of the volcanic rocks, the table mountains have been tilted 1.07° due to uplift of the central Sierra Nevada. While Gabet (2014) suggested that, under a limited set of conditions, the size of fluvial gravels under the table mountains would support the hypothesis of postdepositional uplift, the authors claimed that their evidence is more definitive. In addition, the authors proposed that the central Sierra Nevada tilted as a rigid block. However, their analyses rely on inferences and assumptions that are not supported by field evidence.

Evaluating the role of topographic inversion in the formation of the Stanislaus Table Mountains in the Sierra Nevada (California, USA)

The Table Mountains, a flat-topped series of ridges capped by a 10.4 Ma latite flow in the Stanislaus River watershed, are considered to be evidence for late Cenozoic uplift-driven landscape rejuvenation in the northern Sierra Nevada range (California, USA). The commonly accepted theory for the formation of these mesas posits that the latite flowed and cooled within a bedrock paleovalley and, since then, the surrounding landscape has eroded away, leaving behind the volcanic deposit as a ridge. Although this theory is accepted by many, it has not been thoroughly tested. In this study, I examine a series of geological cross-sections extracted along the length of the latite deposit to determine whether the evidence supports the existence of bedrock valley walls on both sides of the 10.4 Ma flow. I find that the presence of older Cenozoic deposits adjacent to the latite flow precludes the possibility that the flow would have been constrained within a bedrock valley. Moreover, the cross-section from an 1865 report that has been offered as evidence of topographic inversion (and subsequently reproduced in numerous publications) does not accurately represent the topography at that site. I conclude that there is no evidence that the bedrock topography has been inverted and that instead, the latite flowed within a channel cut into underlying Cenozoic deposits, which have since mostly eroded away. This study, therefore, refutes the hypothesis that the Stanislaus River watershed was rejuvenated in the late Cenozoic and challenges the claim for recent significant uplift of the region.

Supplemental Material: Evaluating the role of topographic inversion in the formation of the Stanislaus Table Mountains in the Sierra Nevada (California, USA)

The profile lines and lithological maps.

Supplemental Material: Evaluating the role of topographic inversion in the formation of the Stanislaus Table Mountains in the Sierra Nevada (California, USA)

The profile lines and lithological maps.

From the History of the Studies of the “Cave Town” of Kachi-Kal’on in the Nineteenth and Twentieth Centuries

The “cave towns” are located atop of table mountains built of limestone, or in rocky limestone precipices, within a small section of the Inner Range of the Crimean Mountains in the south-western Crimea. Among a very few written sources on the history of mediaeval Crimea there are mostly narratives, so thorough archaeological study of the sites is essential. Only the analysis of the data obtained by archaeology will shed light on the history of the creation, development, and decline of these enigmatic cave structures. This paper addresses the history of the study of the “cave town” of Kachi-Kal’on. This site is located in the Bakhchisarai District (Republic of the Crimea). Although the travelogues from the eighteenth to the early twentieth century regularly mentioned Kachi-Kal’on, the first archaeological studies of the site were carried out only in 1930. The excavations were conducted at a small square on the promontory in front of the fourth grotto of Kachi-Kal’on, where fortifications of the fortress were allegedly located. The excavations were carried out by the Eski-Kermen Expedition of the State Academy of the History of the Material Culture under the supervision of N. I. Repnikov. In the early autumn 1933, the archaeological researches at Kachi-Kal’on continued by the same expedition. Apart from the investigations in the territory of the ancient town where the cultural layer was disturbed, a great work was done to study and describe the whole site. This paper analyses the circumstances of the said researches of the site and examines the results of these works. The origin and functional purpose of the “cave town” is still disputable. The paper is the first to publish the photographs from the collections of the Institute of the History of the Material Culture of the Russian Academy of Sciences.

Mass tourism in protected areas – underestimated threat? Polish National Parks case study

The article considers the tourist traffic as possible to elements of inanimate nature in protected areas. The highest form of protection in Poland - national parks, has been taken into account. The main goal is to diagnose the situation based on the analysis of official documents elaborated by the national park authorities. One of the important elements is to diagnose the threat to nature and indicate ways to neutralize it. At the beginning, the geotouristic potential of these parks was presented, where this type of resources is considered important from the point of view of tourism. The tourist function of the most important attractions in Poland was indicated. In the top ten there are as many as 4 national parks, including Tatrzański which takes first place. The size of tourist traffic in all 23 parks was analyzed. As a result, it was shown that the most popular, where tourist flow is of mass character, include mountain parks with significant geotouristic potential. Next, the current protection plans for them were analyzed: Tatrzański, Karkonoski, Table Mountains and Pieniński, where the annual tourist flow varies between 0.5 million and almost 4 million visitors per year. Threats were assigned to 4 groups: existing internal threats, potential internal threats, existing external threats and potential external threats. In each of the types of threats special attention was paid to those related to inanimate nature. It also indicated the ways in which park managers want to influence the change of negative trends. The basic conclusion was indicated, which boils down to the postulate of a balanced approach to the protection of both types of nature: animate and inanimate. In the case of animate nature, threats and suggestions for improving the situation seem to be much better diagnosed than in the case of inanimate nature.

Procedural Method for Fast Table Mountains Modelling in Virtual Environments

Natural terrains created by long-term erosion processes can sometimes have spectacular forms and shapes. The visible form depends often upon internal geological structure and materials. One of the unique terrain artefacts occur in the form of table mountains and can be observed in the Monument Valley (Colorado Plateau, USA). In the following article a procedural method is considered for terrain modelling of structures, geometrically similar to the mesas and buttes hills. This method is not intended to simulate physically inspired erosion processes, but targets directly the generation of eroded forms. The results can be used as assets by artists and designers. The proposed terrain model is based on a height-field representation extended by materials and its hardness information. The starting point of the technique is the Poisson Faulting algorithm that was originally used to obtain fractional Brownian surfaces. In the modification, the step function as the fault line generator was replaced with a circular one. The obtained geometry was used for materials’ classification and the hardness part of the modelled terrain. The final model was achieved by the erosive modification of geometry according to the materials and its hardness data. The results are similar to the structures observed in nature and are achieved within an acceptable time for real-time interactions.

Up on the table mountains in Brazil: new Bromeliaceae and Eriocaulaceae (Poales) from the Pantepui in the Guayana Shield

Background and aims – As “islands in the sky” of northern South America, the isolated ecosystems of the Pantepui province include a distinct flora with high levels of endemism and which are ancestral areas for many angiosperm lineages. About one fifth of Pantepui angiosperm species are distributed in Poales, a highly diverse angiosperm order.Methods – Recent field trips were carried out on two Brazilian tepuis, by foot and helicopter. Herbarium collections were consulted and compared with the proposed new species. Key results – Four new species of Poales, three Navia Schult. & Schult.f. (Bromeliaceae) and one Paepalanthus Mart. (Eriocaulaceae) were found. Descriptions, illustrations, and distribution maps of the new species, as well as an identification key to Brazilian Navia species, are provided.

The Influence of Tool Texture on Friction and Lubrication in Strip Reduction Testing

While texturing of workpiece surfaces to promote lubrication in metal forming has been applied for several decades tool surface texturing is rather new. In the present paper tool texturing is studied as a method to prevent galling. Adopting a strip reduction test longitudinal pocket geometries oriented perpendicular to the sliding direction, with shallow pocket depth, small pocket angle to the workpiece surface and varying distance between pockets are investigated. The experiments reveal that the distance between pockets should be larger than the pocket width thereby creating a topography similar to flat table mountains to avoid mechanical interlocking in the valleys; otherwise an increase in drawing load and pick-up on the tools is observed. The textured tool surface lowers friction and improves lubrication performance provided that the distance between pockets is 2-4 times larger than the pocket width. Larger drawing speed facilitates escape of the entrapped lubricant in the pockets. Testing with low to medium viscosity oils leads to a low sheet roughness on the plateaus but also local workpiece material pick-up on the tool plateaus. Large lubricant viscosity results in higher sheet plateau roughness but also prevents pick-up and galling.

New and unusual species of cyanobacteria, diatoms and green algae, with a description of a new genus Ekerewekia gen. nov. (Chlorophyta) from the table mountain Churí-tepui, Chimantá Massif (Venezuela)

The unique character of biotas on table mountains (tepuis) is well documented for macroscopic organisms. However, much less is known about the microorganisms inhabiting these unusual and diverse biotopes. Previously, new algal and cyanobacterial taxa have been described from South American table mountains, providing evidence for the frequently disputed concept of microorganismal endemism. The present study adds additional support for this concept. A number of unusual microalgae were found during a 2012 expedition on the top of Churí-tepui (Chimantá Massif, Venezuela). These organisms were thoroughly examined and we herein propose the establishment of two new species of cyanobacteria—Schizothrix venezuelana sp. nov., Porphyrosiphon latissimus sp. nov., two diatoms—Eunotia churiensis sp. nov. and E. multirimoportulata sp. nov.; and one filamentous green alga, for which we also present molecular phylogenetic support, Ekerewekia churiensis gen. et sp. nov. (Chlorophyta). These novel species are morphologically unique and because no such forms have been reported elsewhere in the world, they are potentially endemic to tepuis.