Large Fall Research Articles

The entry of Colombian-sourced heroin into the US market: The relationship between competition, price, and purity

There have been large structural changes in the US heroin market over the past 20 years. Colombian-sourced heroin entered the market in the mid-1990s, followed by a large fall in the price per pure gram and the exit of Asian heroin. By the 2000s, Colombian-sourced heroin had become a monopoly on the east coast and Mexican-sourced heroin a monopoly on the west coast with competition between the two in the middle. We estimate the relationship between these changes in competitive market structure on retail-level heroin price and purity. We find that the entry of Colombian-sourced heroin is associated with less competition and a lower price per pure gram of heroin at the national level. However, there is wide variation in changes in market concentration across the US. Controlling for the national fall in the heroin price, more competition in a region or city is associated with a lower price per pure gram.

Supporting Evidence for a 9.6 1 ka Rock Fall Originating from Glacier Point in Yosemite Valley, California

Research Article| November 01, 2013 Supporting Evidence for a 9.6 ± 1 ka Rock Fall Originating from Glacier Point in Yosemite Valley, California Shaun E. Cordes; Shaun E. Cordes Department of Geology, Humboldt State University, 1 Harpst Street, Arcata, CA 95521 Search for other works by this author on: GSW Google Scholar Greg M. Stock; Greg M. Stock National Park Service, Yosemite National Park, 5083 Foresta Road P.O. Box 700, El Portal, CA 95318 Search for other works by this author on: GSW Google Scholar Brandon E. Schwab; Brandon E. Schwab Department of Geology, Humboldt State University, 1 Harpst Street, Arcata, CA 95521 Search for other works by this author on: GSW Google Scholar Allen F. Glazner Allen F. Glazner Department of Geological Sciences, CB# 3315, University of North Carolina, Chapel Hill, NC 27599-3315 Search for other works by this author on: GSW Google Scholar Environmental & Engineering Geoscience (2013) 19 (4): 345–361. https://doi.org/10.2113/gseegeosci.19.4.345 Article history 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 Shaun E. Cordes, Greg M. Stock, Brandon E. Schwab, Allen F. Glazner; Supporting Evidence for a 9.6 ± 1 ka Rock Fall Originating from Glacier Point in Yosemite Valley, California. Environmental & Engineering Geoscience 2013;; 19 (4): 345–361. doi: https://doi.org/10.2113/gseegeosci.19.4.345 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 SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract Large boulders exceeding 10 m3 in exposed volume are widely scattered throughout Upper Pines Campground in eastern Yosemite Valley, Yosemite National Park, California. These enigmatic boulders rest up to 330 m from the base of adjacent talus slopes but lack geomorphic expressions typical of other large rock fall, debris flow, or glacial deposits in Yosemite. We evaluated four hypotheses for boulder deposition: (1) glacial deposition during ice retreat 15–17 ka, (2) fluvial deposition during a high-discharge flood event, (3) debris flow deposition, and (4) rock fall deposition. We utilized field mapping, spatial analysis, cosmogenic 10Be exposure dating, and X-ray fluorescence analysis to investigate possible modes of deposition. A mean boulder exposure age of 9.6 ± 1 ka considerably post-dates glacial retreat from Yosemite Valley, effectively ruling out glacial deposition. Discharge and bed stress calculations indicate that although flooding could have been capable of entraining boulders at confined upstream locations, it is unlikely to have transported boulders as far as the Upper Pines area. Slope comparisons and evaluation of surface morphology of debris flow fans in Yosemite Valley suggest that the boulders did not result from debris flows. Geochemical results identify a majority of boulders in Upper Pines as granodiorite of Glacier Point, corresponding to bedrock samples located at the summit of Glacier Point. We interpret boulders in Upper Pines Campground to result from a single large rock fall event originating from the east face of Glacier Point circa 9.6 ± 1 ka; they were subsequently partially buried by alluvial fan aggradation, modifying the original geomorphic expression. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

What Do Data on Millions of U.S. Workers Say About Life Cycle Income Risk?

This paper sheds new light on individual labor income risk using a unique and confidential dataset from the Social Security Administration on individuals' earnings histories. The substantial sample size allows us to cut the data in different and novel ways and document how earnings risk varies over the lifecycle and across individuals that differ in their lifetime income. The main conclusion of our research is that earnings risk varies significantly across the population in the following ways. First, the overall size of income risk becomes smaller with age, from age 25 to 50 and then increases again. Second, as individuals age, the likelihood of getting very small and very large shocks increases relative to the likelihood of middling shocks. Third, income shocks become more left skewed with age, meaning that, relative to the average change in income, a large fall becomes more likely than a large rise as individuals get older. Finally, earnings growth rates are dramatically different for individuals ranked by their lifetime income: individuals with lifetime earnings in the top 5% experience a growth rate from age 25 to 55 that is 10 times larger than individuals with average lifetime earnings. To provide useful input to policy relevant research, we estimate an econometric process that captures these salient features of earnings dynamics to provide a reliable “user's guide” for applied economists.

Quality Assessment of Giant Freshwater Prawn (<i>Macrobrachium rosenbergii</i>) in Ice Storage Condition Collected from Selected Farms and Depots

This study was conducted to evaluate the quality changes in an important crustacean species giant freshwater prawn, Macrobrachium rosenbergii (locally called golda) at various stages of handling. The samples under study were obtained from farms and depots of four golda producing districts viz. Khulna, Bagerhat, Jessore and Norial area by determining organoleptic and biochemical aspects. The golda samples stored in ice immediately after harvest were in acceptable condition for seven days after harvesting period while the samples obtained from depots from all stations were in acceptable condition for 4 days only. There was a large fall of protein solubility and ATPase activity in all the samples obtained from farms and depots. The fall of solubility and ATPase activity was faster in samples obtained from depots compared to the samples obtained from farm immediately after harvest. The large fall of protein solubility and ATPase activity of samples indicated the denaturation of protein during ice storage.DOI: http://dx.doi.org/10.3329/pa.v22i1-2.16476 Progress. Agric. 22(1 & 2): 139-149, 2011

A new species of Exitomelita (Amphipoda: Melitidae) from a deep-water wood fall in the northern Norwegian Sea

The recently erected amphipod genus Exitomelita (Tandberg et al., 2012) has so far been found only associated with the deep-water hydrothermal vent field “Loki's Castle” in the Norwegian-Greenland Sea. There it was found on the black smoker chimney walls as well as within fields of the tubeworm Sclerolinum contortum in sulphide- and methane-rich sediments surrounding the vent field. A new species has now been found in a large wood fall of pine at 2800 m depth close to this vent field. This group of amphipods is apparently confined to reduced habitats, and our data support the theory that the vent fauna in this area is closely related to fauna found on cold seeps and wood falls in the northernmost Atlantic and Arctic Oceans. Here we present morphological and molecular data and a short discussion of the habitat of the new species, in addition to a comparison with the previously described species of Exitomelita.http://www.zoobank.org/urn:lsid:zoobank.org:pub:2B0B3CC2-AB6A-4006-83BB-182280CB22B8

Hemorrhage‐induced increase in total peripheral resistance is blunted in conscious obese Zucker rats

Obesity is associated with increased morbidity and mortality after severe hemorrhage. We hypothesize that in obesity, the blood pressure compensation following severe hemorrhage is impaired due to blunted neurohormonal responses. Mean arterial pressure (MAP) and heart rate (HR) in conscious lean (LZ) and obese Zucker rats (OZ) were monitored before and after injection of SNP or prazosin (iv.) to estimate baroreflex sensitivity or basal sympathetic tone, respectively. Severe hemorrhage (a loss of 35% of total blood volume) was induced in additional groups of conscious LZ and OZ. The MAP, HR, cardiac output (CO), total peripheral resistance (TPR), and plasma renin activity (PRA) were measured before and one hour after hemorrhage. Basal values for MAP, CO, TPR, and PRA were not different between conscious LZ and OZ. However, under basal conditions, prazosin resulted in a larger fall in MAP in OZ (134 ± 3 to 85 ± 4 mmHg) than in LZ (129 ± 4 to 96 ± 4 mmHg). In addition, baroreflex control of HR was impaired in OZ. Following hemorrhage, MAP and HR recovery were more complete in LZ than in OZ. CO was similar in both groups but MAP, TPR, HR, and PRA were significantly lower in OZ than in LZ (Table). These results indicate that the diminished recovery of MAP after hemorrhage in OZ is due to a blunted increase in TPR associated with impaired renin secretion and baroreflex activity. Supported by AHA‐12SDG12050525, NIH HL‐51971, and HL‐89581

Comment

Comment

Falls Among Adult Patients Hospitalized in the United States

The purpose of this study was to provide normative data on fall prevalence in U.S. hospitals by unit type and to determine the 27-month secular trend in falls before the implementation of the Centers for Medicare and Medicaid Service (CMS) rule, which does not reimburse hospitals for care related to injury resulting from hospital falls. We used data from the National Database of Nursing Quality Indicators (NDNQI) collected between July 1, 2006, and September 30, 2008, to estimate prevalence and secular trends of falls occurring in adult medical, medical-surgical, and surgical nursing units. More than 88 million patient days (pd) of observation were contributed from 6100 medical, surgical, and medical-surgical nursing units in 1263 hospitals across the United States. A total of 315,817 falls occurred (rate = 3.56 falls/1000 pd) during the study period, of which, 82,332 (26.1%) resulted in an injury (rate = 0.93/1000 pd). Both total fall and injurious fall rates were highest in medical units (fall rate = 4.03/1000 pd; injurious fall rate = 1.08/1000 pd) and lowest in surgery units (fall rate = 2.76/1000 pd; injurious fall rate = 0.67/1000 pd). Falls (0.4% decrease per quarter, P < 0.0001) and injurious falls (1% decrease per quarter, P < 0.0001) both decreased over the 27-month study. In this large sample, fall and injurious fall prevalence varied by nursing unit type in U.S. hospitals. Over the 27-month study, there was a small, but statistically significant, decrease in falls (P < 0.0001) and injurious falls (P < 0.0001).

Revenge of the Optimum Currency Area

Revenge of the Optimum Currency Area

Variation in the Hatteras Front density and velocity structure Part 2: Historical setting

On the continental shelf near Cape Hatteras, cool fresh Mid-Atlantic Bight and warm salty South Atlantic Bight shelf waters converge alongshelf 90% of the time, causing strong alongshelf gradients in temperature and salinity known as the ‘Hatteras Front’. The resulting density gradient supports strong shoreward velocities in the cross-shelf oriented ‘nose’, of the Front in wintertime. To investigate further, the Frontal Interactions near Cape Hatteras (FINCH) project used shipboard ADCP and a towed undulating CTD to examine Hatteras Front property, density and velocity fields in August 2004, January 2005, and July 2005. Strong property gradients were encountered across the nose of the Hatteras Front in all cases, but the density gradient, dynamic height gradient, and observed along-front cross-shelf velocities evolved in time. FINCH along-Front velocities were strong and shoreward in fall and winter, and weakly mixed shoreward and seaward in July. Several archived data sets were examined, and demonstrate that the density evolution and wind forcing seen in FINCH are characteristic of other years. Evidence suggests the width of the Hatteras Front does not vary dramatically in time, so that consistently large fall and winter density contrast across the Front implies consistently large shoreward velocities along it in winter. Weak density contrasts across the Hatteras Front in spring suggest the magnitude and sign of springtime density gradients and along-Front velocities could vary interannually. Recruitment success of commercially important stocks on the shelf that depend on cross-shelf transport may thus be affected year to year.

Sea level and vertical motion of continents from dynamic earth models since the Late Cretaceous

Dynamic earth models are used to better understand the impact of mantle dynamics on the vertical motion of continents and regional and global sea level change since the Late Cretaceous. A hybrid approach combines inverse and forward models of mantle convection and accounts for the principal contributors to long-term sea level change: the evolving distribution of ocean floor age, dynamic topography in oceanic and continental regions, and the geoid. We infer the relative importance of dynamic versus other factors of sea level change, determine time-dependent patterns of dynamic subsidence and uplift of continents, and derive a sea level curve. We find that both dynamic factors and the evolving distribution of sea floor age are important in controlling sea level. We track the movement of continents over large-scale dynamic topography by consistently mapping between mantle and plate frames of reference, and we find that this movement results in dynamic subsidence and uplift of continents. The amplitude of dynamic topography in continental regions is larger than global sea level in several regions and periods, so that it has controlled regional sea level in North and South America and Australia since the Late Cretaceous, northern Africa and Arabia since the late Eocene, and Southeast Asia in the Oligocene–Miocene. Eastern and southern Africa have experienced dynamic uplift over the last 20 to 30 m.y., whereas Siberia and Australia have experienced Cenozoic tilting. The dominant factor controlling global sea level is a changing oceanic lithosphere production that has resulted in a large amplitude sea level fall since the Late Cretaceous, with dynamic topography offsetting this fall.

The Impact of Housing Market Conditions on Residential Property Upkeep

This paper assesses the impact of housing market conditions on the theoretically motivated and empirically observed negative relationship between loan-to-value (LTV) ratios and home maintenance expenditures. If the relationship is causal, then a down housing market will result in significantly decreased upkeep in the housing stock. The large rise and fall in home prices during the 2001–2009 period allows a unique opportunity to analyze the response of homeowners to changing housing market conditions. Data from the American Housing Survey are analyzed to confirm previous work that a negative relationship exists between LTV ratios and routine maintenance expenditures, however, this relationship does not move in the expected direction when examined along with temporal variations in market conditions. Panel analysis reveals a more complex story. Households most likely to be at risk for default decrease maintenance expenditures when default risk increases, but other households actually increased maintenance expenditures when the housing market conditions became less favorable.

Ionisers for chronic asthma.

Previous reports have shown that ion content in the air may have an effect on respiratory function. Results from studies which test the efficacy of air ionisers to reduce asthma symptoms are often inconclusive and their use as a treatment for asthma remains debatable. We conducted a systematic review of the available evidence to determine the effectiveness of positive and negative ion generators in people with asthma. We searched the Cochrane Airways Group Specialised Register, Cochrane Central Register of Controlled Trials (CENTRAL) as well as the alternative medicine database AMED. Searches were current as of June 2012. Randomised controlled trials (parallel or crossover design studies) comparing ionisers with dummy ionisers (being negative or positive ion emitters), in children or adults with chronic asthma. Two reviewers independently assessed titles and abstracts of studies and assessed trial quality. Study quality was determined using two methods:The Cochrane approach to allocation concealment and the five point Jadad scale. Six studies were selected for inclusion (106 participants). No results were combined as the studies were all of a crossover design.EFFECTS OF NEGATIVE ION GENERATORS (five studies) No study reported a significant difference in lung function between ionised and control air (morning Peak expiratory flow (PEF) - three studies; forced expiratory flow in one second (FEV1) - one study). There were no significant differences in symptoms or beta-2 agonist usage between ionised and control air in three studies.EFFECTS OF POSITIVE ION GENERATORS (one study) This study demonstrated that although positively ionised air was associated with a larger fall in FEV1 with exercise, this did not reach statistical significance. Baseline FEV1 was not demonstrated to be significantly different between treatment groups. Based on the evidence currently available from randomised controlled trials, a recommendation cannot be given for the use of room air ionisers to reduce symptoms in patients with chronic asthma.

Abstract 658: Pressor And Sympathetic Response To 2% Saline Augmented By Prior Treatment With Intracerebroventricular (icv) Angiotensin II (ANGII)

Previous studies from our laboratory demonstrate that the sensitizing effects of sub-pressor ANGII or aldosterone treatments on ANGII-induced hypertension are mediated through the CNS. The present study tested if pressor response sensitization extends to another hypertensive challenge, 2% saline given as the sole drinking fluid. The study followed an Induction-Delay-Expression ( I-D-E ) experimental design. We instrumented rats with telemetry devices to continuously record blood pressure (BP) and heart rate throughout the experiments. After one week recovery and one week baseline ( B ) recording, rats underwent a second surgery to implant icv cannulas to continuously deliver ANGII (1 ng/kg/min; prior ANGII) or vehicle (control) for one week ( I ). After I and after a 1 week D , drinking water was switched to 2% saline ( E ). The degree of autonomic tone was assessed via ganglionic blockade (hexamethonium, 30 mg/kg, ip) during B , after I , and during E . During B, group BPs were not different (103±2 mmHg control vs. 107±4mmHg, prior-ANGII). Although drinking only 2% saline increased BPs in both groups (122±3 mmHg, control vs. 141±9 mmHg, prior-ANGII), the absolute increase was greater in rats treated with ANGII during I (19±3, control vs. 34±6, prior-ANGII, p&lt;0.05). At B, control and prior-ANGII treated rats showed no difference in the depressor response to hexamethonium (-17±3%, control vs. -13±1%, prior-ANGII) or after I (-13±5%, control vs. -20±9%, prior-ANGII). However, during E while drinking2% saline, prior-ANGII treated rats displayed a significantly larger fall in BP to hexamethonium than controls (-20±5%, control vs. -36±7%, prior-ANGII, p&lt;0.05), suggesting that during E a higher degree of sympathetic tone maintained BP in the prior-ANGII treated rats. These data show that icv treatment with ANGII sensitizes the hypertensive response induced by 2% saline intake and that this enhanced pressor effect is accompanied by elevated sympathetic tone. These results provide new insights into the etiology of salt-sensitive hypertension by implicating a role for ANGII-induced neuroplasticity in CNS systems controlling sympathetic tone.

Temporal and spatial variability in fall storm induced sediment resuspension on the Mid-Atlantic Bight

Storm-driven sediment resuspension is an episodic process that is an important constraint on sediment transport on continental shelves; unfortunately, the spatial variability of the resuspension and transport processes are poorly quantified using traditional sampling techniques. Using two autonomous underwater gliders, long-range high frequency radar and buoy data, we quantified spatial variability of sediment resuspension and transport in a large fall storm in November of 2009. Wave, wind and current data in conjunction with glider profiles showed that waves and winds mixed the water column, waves initially mobilized the sediment and shear induced turbulence advected sediment throughout the water column. The separation of over 50km between the two gliders (RU05 and RU21) is used to highlight the spatial variability of sediment resuspension. Both gliders were operating along the 40m isobath with RU21 located 50km north of RU05. Sediment resuspension on the New Jersey (NJ) shelf responded to synoptically forced turbulent motions. Currents transported this sediment toward the southwest in the along-shelf axis and onshore on the cross-shelf axis during the peak resuspension on November 13th through November 14th, with resuspension and transport on the southern NJ shelf measured by RU05 approximately twice that of RU21 on the northern MAB. Variability in resuspension profiles between the two gliders was largely a product of smaller mean grain sizes on the southern portion of the NJ shelf. These smaller grain sediment particles had a reduced fall velocity and were more easily retained throughout the water column by turbulent motions.

An Acute Infusion of Lactic Acid Lowers the Concentration of Potassium in Arterial Plasma by Inducing a Shift of Potassium into Cells of the Liver in Fed Rats

Background: Potassium (K⁺) input occurs after meals or during ischemic exercise and is accompanied by a high concentration of L-lactate in plasma (P_L-lactate). Methods: We examined whether infusing 100 µmol L-lactic acid/min for 15 min would lead to a fall in the arterial plasma K⁺ concentration (P_K). We also aimed to evaluate the mechanisms involved in normal rats compared with rats with acute hyperkalemia caused by a shift of K⁺ from cells or a positive K⁺ balance. Results: There was a significant fall in P_K in normal rats (0.25 mM) and a larger fall in P_K in both models of acute hyperkalemia (0.6 mM) when the P_L-lactate rose. The arterial P_K increased by 0.8 mM (p < 0.05) 7 min after stopping this infusion despite a 2-fold rise in the concentration of insulin in arterial plasma (P_Insulin). There was a significant uptake of K⁺ by the liver, but not by skeletal muscle. In rats pretreated with somatostatin, P_Insulin was low and infusing L-lactic acid failed to lower the P_K. Conclusions: A rise in the P_L-lactate in portal venous blood led to a fall in the P_K and insulin was permissive. Absorption of glucose by the Na⁺-linked glucose transporter permits enterocytes to produce enough ADP to augment aerobic glycolysis, raising the P_L-lactate in the portal vein to prevent postprandial hyperkalemia.

Stratigraphic Hierarchy and Shelf-to-Basin Architecture of Aptian–Albian Mural Shelf, Cerro Caloso Range, Sonora, Mexico

The Mural-Caloso Shelf in Sonora, Mexico is one of only a limited number of outcrops that provide continuous shelf-to-basin profiles of reef-rimmed carbonate platforms with well-defined lowstand deposits and documentable downward shifts in coastal onlap. This paper examines the shelf-to-basin transition across three thirdorder sequences at the Cerro Caloso outcrop. Four parameters: reef framestone lateral and vertical dimensions, fore-reef slope lateral and vertical dimensions, evolution of platform interior facies, and presence or absence of lowstand systems tract siliciclastic wedges with or without mixed oolitic grainstone were used as the basis for the characterization of the shelf to basin profile evolution. The lower two sequences (S3 and S4) are mostly aggradational with broad coral-rudist reef rimmed margins and thick platform interiors dominated by carbonate facies. The uppermost sequence (S5) is progradational and downstepping with a narrow coralrudist reef rimmed margin and a thin siliciclastic-rich platform interior. A lowstand wedge of fine-medium grained sandstone and cross-bedded oolitic grainstones that onlaps the S4 coralrudist margin documents downstepping and a minimum of 20 m of downward shift in coastal onlap. The lower sequence wedge is relatively thin compared to the thickness of the S5 wedge. The long-term progradation and increased clastic component observed in the latter stages of shelf evolution indicate a large second order relative sea level fall during the deposition of the Lower Albian age Mural-Caloso Shelf. The continuous outcrop provides a good reference model for facies patterns and stratigraphic architecture for the time equivalent Cretaceous platforms that develop similar geometries such as the Shuiba shelf in the Middle East.

Mechanism of the lung-deflating action of the canine diaphragm at extreme lung inflation

When lung volume in animals is passively increased beyond total lung capacity (TLC; transrespiratory pressure = +30 cmH(2)O), stimulation of the phrenic nerves causes a rise, rather than a fall, in pleural pressure. It has been suggested that this was the result of inward displacement of the lower ribs, but the mechanism is uncertain. In the present study, radiopaque markers were attached to muscle bundles in the midcostal region of the diaphragm and to the tenth rib pair in five dogs, and computed tomography was used to measure the displacement, length, and configuration of the muscle and the displacement of the lower ribs during relaxation at seven different lung volumes up to +60 cmH(2)O transrespiratory pressure and during phrenic nerve stimulation at the same lung volumes. The data showed that 1) during phrenic nerve stimulation at 60 cmH(2)O, airway opening pressure increased by 1.5 ± 0.7 cmH(2)O; 2) the dome of the diaphragm and the lower ribs were essentially stationary during such stimulation, but the muscle fibers still shortened significantly; 3) with passive inflation beyond TLC, an area with a cranial concavity appeared at the periphery of the costal portion of the diaphragm, forming a groove along the ventral third of the rib cage; and 4) this area decreased markedly in size or disappeared during phrenic stimulation. It is concluded that the lung-deflating action of the isolated diaphragm beyond TLC is primarily related to the invaginations in the muscle caused by the acute margins of the lower lung lobes. These findings also suggest that the inspiratory inward displacement of the lower ribs commonly observed in patients with emphysema (Hoover's sign) requires not only a marked hyperinflation but also a large fall in pleural pressure.

Rock fall dynamics and deposition: an integrated analysis of the 2009 Ahwiyah Point rock fall, Yosemite National Park, USA

ABSTRACTWe analyzed a combination of airborne and terrestrial LiDAR, high‐resolution photography, seismic, and acoustic data in order to gain insights into the initiation, dynamics, and talus deposition of a complex rock fall. A large (46 700 m3) rock fall originated from near Ahwiyah Point in eastern Yosemite Valley and fell a total of 730 m to the valley floor on 28 March 2009. Analyses of remote sensing, seismic, and acoustic data were integrated to reconstruct the rock fall, which consisted of (1) the triggering of a 25 400 m3 rock block in an area of intersecting and sometimes highly weathered joint planes, (2) the sliding and subsequent ballistic trajectory of the block from a steeply dipping ledge, (3) dislodging of additional rock from the cliff surface from beneath the rock fall source area, (4) a mid‐cliff ledge impact that detached a volume of rock nearly equivalent in volume to the initial block, (5) sliding of the deteriorating rock mass down the remainder of the cliff, and (6) final impact at the base of the cliff that remobilized the existing talus downward and outward and produced an airblast that knocked down hundreds of trees. The depositional geomorphology indicates that the porosity of the fresh talus is significantly lower than that expected for typical blocky talus slopes, likely because the rock debris from this event was pulverized into smaller, more poorly sorted fragments and densified via dynamic compaction when compared to less energetic, fragmental‐type rock falls. These results suggest that accumulation of individual rock‐fall boulders tends to steepen talus slopes, whereas large, energetic rock falls tend to flatten them. Detachment and impact signals were recorded by seismic and acoustic instruments and highlight the potential use of this type of instrumentation for generalized rock fall monitoring, while LiDAR and photography data were able to quantify the cliff geometry, rock fall volume, source and impact locations, and geomorphological changes to the cliff and talus. Published in 2012. This article is a US Government work and is in the public domain in the USA.

Cornice dynamics and meteorological control at Gruvefjellet, Central Svalbard

Abstract. Cornice fall avalanches endanger life and infrastructure in Nybyen, a part of Svalbard's main settlement Longyearbyen, located at 78° N in the High Arctic. Thus, cornice dynamics – accretion, cracking and eventual failure – and their controlling meteorological factors were studied along the ridgeline of the Gruvefjellet plateau mountain above Nybyen in the period 2008–2010. Using two automatic time-lapse cameras and hourly meteorological data in combination with intensive field observations on the Gruvefjellet plateau, cornice process dynamics were investigated in larger detail than previously possible. Cornice accretion starts directly following the first snowfall in late September and October, and proceeds throughout the entire snow season under a wide range of air temperature conditions that the maritime winter climate of Svalbard provides. Cornice accretion is particularly controlled by distinct storm events, with a prevailing wind direction perpendicular to the ridge line and average wind speeds from 12 m s−1. Particularly high wind speeds in excess of 30 m s−1 towards the plateau ridgeline lead to cornice scouring and reduce the cornice mass both vertically and horizontally. Induced by pronounced air temperature fluctuations which might reach above freezing and lead to midwinter rainfall events, tension cracks develop between the cornice mass and the plateau. Our measurements indicate a linear crack opening due to snow creep and tilt of the cornice around a pivot point. Four to five weeks elapsed between the first observations of a cornice crack until cornice failure. Throughout the two snow seasons studied, 180 cornice failures were recorded, of which 70 failures were categorized as distinctive cornice fall avalanches. A clear temporal pattern with the majority of cornice failures in June was found. Thus only daily air temperature could determine avalanche from non-avalanche days. Seven large cornice fall avalanches reached the avalanche fans on which the Nybyen settlement is located. The size of the avalanches was primarily determined by the size of the cornice that detached. The improved process understanding of the cornice dynamics provides a first step towards a better predictability of this natural hazard, but also highlights that any type of warning based on meteorological factors is not an adequate measure to ensure safety of the housing at risk.