Foehn Winds of Southern California

One of the characteristic weather phenomena of southern California is a wind of the foehn type known locally as the Santa Ana. Unseasonably high temperatures and very low humidities are associated with its occurence. The maximum effects of this wind are felt in the region south of Cajon Pass at the eastern extremity of the Los Angeles Basin. The latter area, extending eastward from the sea to the San Bernardino Mountains, is ordinarily protected from continental influences by the rather high San Gabriel Mountains to the north. Cajon Pass, trending roughly north and south between the San Gabriel Mountains to the west and the San Bernardino Mountains to the east, opens to the north upon the Mohave Desert and to the south upon the alluvial plain of the Los Angeles Basin

The Rwenzori Mountains, a Paleoproterzoic crustal shear belt crossing the Albertine rift system

This contribution discusses the development of the Paleoproterozoic Buganda-Toro belt in the Rwenzori mountains and its influence on the western part of the East African Rift System in Uganda. The Buganda-Toro belt is composed of several thick-skinned nappes consisting of Archaean Gneisses and Palaeoproterozoic cover units that are thrusted northwards. The high Rwenzori mountains are located in the frontal unit of this belt with retrograde greenschist facies gneisses towards the north, which are unconformably overlain by metasediments and amphibolites. Towards the south the metasediments are overthrust by the next migmatitic gneiss unit that belongs to a crustal scale nappe. The southwards dipping metasedimentary and volcanic sequence in the high Rwenzori mountains shows an inverse metamorphic grade with greenschist facies conditions in the north and amphibolite facies conditions in the south. Early D1 deformation structures are overgrown by cordierite, which in turn grows into D2 deformation, representing the major northwards directed thrusting event. We argue that the inverse metamorphic gradient develops because higher grade rocks are exhumed in the footwall of a crustal scale nappe whereas the exhumation decreases towards the north away from the nappe leading to a decrease in metamorphic grade. The D2 deformation event is followed by a D3 E-W compression, a D4 with the development of steep shear zones with a NNE-SSW and SSE-NNW trend including the large Nyamwamba shear followed by a local D5 retrograde event and D6 brittle inverse faulting. The Paleoproterozoic Buganda-Toro belt is relatively stiff and crosses the NNE-SSW running rift system exactly at the node where the highest peaks of the Rwenzori mountains are situated and where the lake George rift terminates towards the north. Orientation of brittle and ductile fabrics show some similarities indicating that the cross-cutting Buganda-Toro belt influenced rift propagation and brittle fault development within the Rwenzori mountain and that this stiff belt may form part of the reason why the Rwenzori mountains are relatively high within the rift. Keywords: East African Rift, Basement, Buganda Toro, Inverse Metamorphic Gradient, Microtectonics, Rwenzori mountain

Taxonomic results of the Bryotrop expedition to Zaire and Rwanda : 31., the Andean Daltonia latolimbata Broth. in Herzog in Africa

Daltonia latolimbata Broth. described in 1916 from the Bolivian Andes occurs also in the high African mountains, consequently is an Andean-Afroalpine species

Mid-Miocene cooling and the extinction of tundra in continental Antarctica

A major obstacle in understanding the evolution of Cenozoic climate has been the lack of well dated terrestrial evidence from high-latitude, glaciated regions. Here, we report the discovery of exceptionally well preserved fossils of lacustrine and terrestrial organisms from the McMurdo Dry Valleys sector of the Transantarctic Mountains for which we have established a precise radiometric chronology. The fossils, which include diatoms, palynomorphs, mosses, ostracodes, and insects, represent the last vestige of a tundra community that inhabited the mountains before stepped cooling that first brought a full polar climate to Antarctica. Paleoecological analyses, 40Ar/39Ar analyses of associated ash fall, and climate inferences from glaciological modeling together suggest that mean summer temperatures in the region cooled by at least 8°C between 14.07 ± 0.05 Ma and 13.85 ± 0.03 Ma. These results provide novel constraints for the timing and amplitude of middle-Miocene cooling in Antarctica and reveal the ecological legacy of this global climate transition

Airborne Thermal Infrared Multispectral Scanner (TIMS) images over disseminated gold deposits, Osgood Mountains, Humboldt County, Nevada

The U.S. Geological Survey (USGS) acquired airborne Thermal Infrared Multispectral Scanner (TIMS) images over several disseminated gold deposits in northern Nevada in 1983. The aerial surveys were flown to determine whether TIMS data could depict jasperoids (siliceous replacement bodies) associated with the gold deposits. The TIMS data were collected over the Pinson and Getchell Mines in the Osgood Mountains, the Carlin, Maggie Creek, Bootstrap, and other mines in the Tuscarora Mountains, and the Jerritt Canyon Mine in the Independence Mountains. The TIMS data seem to be a useful supplement to conventional geochemical exploration for disseminated gold deposits in the western United States. Siliceous outcrops are readily separable in the TIMS image from other types of host rocks. Different forms of silicification are not readily separable, yet, due to limitations of spatial resolution and spectral dynamic range. Features associated with the disseminated gold deposits, such as the large intrusive bodies and fault structures, are also resolvable on TIMS data. Inclusion of high-resolution thermal inertia data would be a useful supplement to the TIMS data

Degree Landscapes in Scale-Free Networks

We generalize the degree-organizational view of real-world networks with broad degree-distributions in a landscape analogue with mountains (high-degree nodes) and valleys (low-degree nodes). For example, correlated degrees between adjacent nodes corresponds to smooth landscapes (social networks), hierarchical networks to one-mountain landscapes (the Internet), and degree-disassortative networks without hierarchical features to rough landscapes with several mountains. We also generate ridge landscapes to model networks organized under constraints imposed by the space the networks are embedded in, associated to spatial or, in molecular networks, to functional localization. To quantify the topology, we here measure the widths of the mountains and the separation between different mountains.Comment: 4 pages, 5 figure

Bird Migration Through A Mountain Pass Studied With High Resolution Radar, Ceilometers, And Census

Autumnal migration was studied with high-resolution radar, ceilometer, and daily census in the area of Franconia Notch, a major pass in the northern Appalachian Mountains. Under synoptic conditions favorable for migration, broadfront movements of migrants toward the south passed over the mountains, often above a temperature inversion. Birds at lower elevations appeared to be influenced by local topography. Birds moving southwest were concentrated along the face of the mountain range. Birds appeared to deviate their flights to follow local topography through the pass. Specific migratory behavior was not associated with species or species groups. Under synoptic conditions unfavorable for southward migration, multimodal movements probably associated with local flights were as dense as the southward migrations described above. Avian migrants reacting to local terrain may result in concentrations of migrants over ridge summits or other topographic features

Remote sensing and geologic studies of the orientale basin region

Both visual and near-infrared spectral observations are combined with multispectral imaging to study the Orientale interior and exterior, the Cruger region, Grimaldi Region, the Schiller-Schickard Region, and the Humorum Region of the Moon. It was concluded that anorthosites occur in the Inner Rook Mountains of Orientale, the inner ring of Grimaldi, and the main ring of Humorum. Imaging spectroscopy shows that the entire eastern Inner Rook Mountains are composed of anorthosites. Orientale ejecta are strikingly like the surface materials in the region where Apollo 16 landed. This similarity indicates similar mineralogy, i.e., noritic anorthosite. Thus, Orientile ejecta is more mafic than the Inner Rook Mountains. This situation is also true for the Nectaris, Humorum, and Gramaldi basins. Isolated areas of the Orientale region show the presence of gabbroic rocks, but, in general, Orientale ejecta are noritic anorthosites, which contain much more low-Ca pyroxene than high-Ca pyroxene. Ancient (pre-Orientale) mare volcanism apparently occurred in several areas of the western limb

The next widespread bamboo flowering poses a massive risk to the giant panda

The IUCN Red List has downgraded several species from “endangered” to “vulnerable” that still have largely unknown extinction risks. We consider one of those downgraded species, the giant panda, a bamboo specialist. Massive bamboo flowering could be a natural disaster for giant pandas. Using scenario analysis, we explored possible impacts of the next bamboo flowering in the Qinling and Minshan Mountains that are home to most giant pandas. Our results showed that the Qinling Mountains could experience large-scale bamboo flowering leading to a high risk of widespread food shortages for the giant pandas by 2020. The Minshan Mountains could similarly experience a large-scale bamboo flowering with a high risk for giant pandas between 2020 and 2030 without suitable alternative habitat in the surrounding areas. These scenarios highlight thus-far unforeseen dangers of conserving giant pandas in a fragmented habitat. We recommend advance measures to protect giant panda from severe population crashes when flowering happens. This study also suggests the need to anticipate and manage long-term risks to other downgraded species