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Article Highlights


Also of Interest


Article Highlights

Boulder deposition by tsunamis and storms

A study explores the origin of boulders deposited on cliffs in western Ireland and New Zealand’s North Island. The question of whether tsunamis or storm waves are responsible for the presence of boulders on ocean cliffs remains unsettled. John Dewey and Paul Ryan compared two deposits of boulders weighing more than 30 tonnes on the coastline of Annagh Head, western Ireland and on the Matheson Formation, a Miocene deposit in New Zealand. Oceanographic data, field measurements, and historic storm accounts indicated that Annagh Head deposits, which weigh more than 50 tonnes, are subject to 20-30-meter-high storm waves. Field measurements of the Matheson Formation indicated that a 12-13-meter tsunami with a period of approximately 1 hour could have deposited the boulders, some of which weigh more than 140 tonnes. Further, compared with the Annagh Head deposits, the Matheson Formation deposits are spread over a large geographic region and include a large proportion of ocean floor sediments—both of which are indicative of a tsunami. A numerical model of storm waves indicated that boulder size, shape, and density determine the site at which waves deposit boulders. According to the authors, the Matheson Formation likely represents the deposition of a single tsunami over 1 hour, whereas the Annagh Head deposits likely represent the result of centuries of storms.

“Storm, rogue wave, or tsunami origin for megaclast deposits in western Ireland and North Island, New Zealand?,” by John F. Dewey and Paul D. Ryan
10.1073/pnas.1713233114

abstract


Hydraulic fracturing and groundwater wells

A study examines the proximity of domestic groundwater wells to hydraulically fractured oil and gas wells in the United States. Self-supply groundwater wells provide drinking water to around 45 million Americans. The number of self-supply or public-supply water wells that are in close proximity to hydraulic fracturing operations and at risk of potential contamination remains unestablished. Scott Jasechko and Debra Perrone determined the distances between domestic groundwater wells constructed between 2000 and 2014 and hydraulically fractured oil and gas wells stimulated in 2014 in 14 states. Of the nearly 27,000 wells stimulated in 2014, 37% were within 2 km of at least one domestic groundwater well, and 60% were within 3 km of at least one domestic groundwater well. In 11 counties, a majority of domestic groundwater wells were within 2 km of a hydraulically fractured well, whereas a majority of domestic groundwater wells were within 2 km of a producing oil and gas well in 236 counties. The results suggest the importance of increased water quality monitoring efforts near hydraulic fracturing and conventional oil and gas wells to determine the risk of contamination and to protect well water quality. The results also identify hotspots of water wells in proximity to oil and gas wells where such efforts could be targeted, according to the authors.

“Hydraulic fracturing near domestic groundwater wells,” by Scott Jasechko and Debra Perrone
10.1073/pnas.1701682114

abstract


Also of Interest

Pollinator preference across environments

To study the preferences of insect pollinators across environments, researchers sampled flowers for floral cues that attracted pollinators, namely hoverflies, in three environments: hemiboreal Sweden, the alpine Himalayas, and tropical South India; using artificial models based on floral cues, the authors found that some models attracted hoverflies in every environment, even though specific combinations of floral cues did not represent those of real flowers, findings with potential implications for establishing planting strategies resilient to environmental change, according to the authors.

“In situ modeling of multimodal floral cues attracting wild pollinators across environments,” by Karin Nordstr?m, et al.
10.1073/pnas.1714414114

abstract


Fluid-driven artificial muscles

Researchers report a fluid-driven artificial muscle that incorporates a compressible skeleton architecture, a flexible skin covering, and a fluid medium to direct the action of the muscle; the artificial muscle can be manufactured with various materials at multiples scales and execute motions including bending, contraction, and torsion, with the ability to contract more than 90% of its initial length and generate stresses of approximately 600 kPa, according to the authors.

“Fluid-driven origami-inspired artificial muscles,” by Shuguang Li, et al.
10.1073/pnas.1713450114

abstract


Ectotherms and climate change

A model based on life history trait data from different latitudes predicts that ectotherm populations are likely to peak earlier in the year as mean local temperatures rise, but that the populations are likely to peak later in the year if the intensity of seasonal temperature fluctuations increases; warming was not associated with longer activity periods in high-latitude species, because summer temperatures often rose above the animals’ physiological limits, providing insights into the potential influence of temperature on the seasonal timing of life history events for ectotherms.

“Predicting phenological shifts in a changing climate,” by Katherine Scranton and Priyanga Amarasekare
10.1073/pnas.1711221114

abstract


Late Quaternary European dust and climate

Accelerator mass spectrometry radiocarbon dating of small gastropods in loess soil from Hungary suggests that rapid changes in late Quaternary North Atlantic temperature and glacial dust activity in East Central Europe and Greenland were largely synchronous, according to a study; the authors suggest that fluctuations in precipitation and atmospheric circulation as well as the North Atlantic Oscillation may have influenced European dust activity.

“Coupled European and Greenland last glacial dust activity driven by North Atlantic climate,” by Gábor újvári, et al.
10.1073/pnas.1712651114

abstract


Ice sheets, carbon dioxide, and climate change

Boron isotope based carbon dioxide (CO2) data in combination with modelling indicates that dust-borne iron fertilization of the Southern Ocean during Mid-Pleistocene Transition glacial periods may have led to a decrease in glacial CO2 concentrations; further analyses of the CO2 record and sea-level data suggest that CO2 reductions due to iron fertilization may have yielded stronger and longer glaciations following the Mid-Pleistocene Transition, according to a study.

“Causes of ice age intensification across the Mid-Pleistocene Transition,” by Thomas B. Chalk, et al.
10.1073/pnas.1702143114

abstract


Prenatal stress and offspring growth

In a comparative analysis across 21 mammal species in 719 studies, researchers report the effects of prenatal maternal stress (PREMS) on offspring growth, and suggest that PREMS likely reduces maternal investment toward offspring and accelerates offspring growth and development, with increased growth rates being linked to PREMS exposure during early gestation, highlighting a potential adaptive role for PREMS, according to the authors.

“Prenatal stress accelerates offspring growth to compensate for reduced maternal investment across mammals,” by Andreas Bergh?nel, Michael Heistermann, Oliver Schülke, and Julia Ostner
10.1073/pnas.1707152114

abstract

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