Groundwater sapping channels: Summary of effects of experiments with varied stratigraphy

Experiments in the recirculating flume sapping box have modeled valley formation by groundwater sapping processes in a number of settings. The effects of the following parameters on sapping channel morphology were examined: surface slope; stratigraphic variations in permeability cohesion and dip; and structure of joints and dikes. These kinds of modeling experiments are particularly good for: testing concepts; developing a suite of distinctive morphologies and morphometries indicative of sapping; helping to relate process to morphology; and providing data necessary to assess the relative importance of runoff, sapping, and mass wasting processes on channel development. The observations from the flume systems can be used to help interpret features observed in terrestrial and Martian settings where sapping processes are thought to have played an important role in the development of valley networks

Threshold phenomena in erosion driven by subsurface flow

We study channelization and slope destabilization driven by subsurface (groundwater) flow in a laboratory experiment. The pressure of the water entering the sandpile from below as well as the slope of the sandpile are varied. We present quantitative understanding of the three modes of sediment mobilization in this experiment: surface erosion, fluidization, and slumping. The onset of erosion is controlled not only by shear stresses caused by surfical flows, but also hydrodynamic stresses deriving from subsurface flows. These additional forces require modification of the critical Shields criterion. Whereas surface flows alone can mobilize surface grains only when the water flux exceeds a threshold, subsurface flows cause this threshold to vanish at slopes steeper than a critical angle substantially smaller than the maximum angle of stability. Slopes above this critical angle are unstable to channelization by any amount of fluid reaching the surface.Comment: 9 pages, 11 figure

trans-(2,2′-Bipyrimidine)diiodido(isopropoxido)oxidorhenium(V)

In the title compound, [Re(C3H7O)I2O(C8H6N4)], the ReV atom adopts a distorted octa­hedral ReI2O2N2 geometry, with the O atoms in a trans conformation and the I atoms in a cis conformation. Two intra­molecular C—H⋯I contacts occur. The crystal structure is stabilized by inter­molecular C—H⋯O, C—H⋯N and C—H⋯I hydrogen bonds

Assessing the Initial Impact of the Michael Brown Shooting and Police and Public Responses to it on St Louis County Residents\u27 Views about Police

A panel survey of nearly four hundred St. Louis County, MO residents both before and after the shooting death of Michael Brown reveal a dramatic impact of that incident and the civil unrest and police handling of the unrest on residents perceptions of police. African American residents, on average, supported the public’s response to the police shooting but disagreed with the police response to the protests, looting and riots that followed, while nonblack residents’ views were just the opposite. Additionally, in the time immediately following the shooting, African American residents’ trust in police procedural justice and perceptions of police legitimacy declined by twenty-six and eight percent respectively, while non-black residents saw non-significant improvements in perceptions of procedural justice and legitimacy. Although residents of both racial backgrounds reported increases in aggressive policing tactics during that time, African American residents reported significantly greater increases—in fact, a twenty-one percent increase in the frequency of aggressive tactics. Where views did not differ by race was that residents of both races supported the use of body or dash cameras, focus groups of residents and police to discuss police practices, and more frequent police patrols to improve confidence and trust in police

Views By St Louis County Residents Regarding the Police and Public Responses to the Shooting of Michael Brown in Ferguson, Missouri on August 9, 2014

In their own words, residents living in high crime, disadvantaged neighborhoods of St. Louis County, MO revealed how they were personally impacted by the shooting of Michael Brown in Ferguson and the police and public response to it during the first few weeks following the event last August. Three quarters of residents reported being impacted in some way. The most common negative effects were emotional, as well as the daily inconvenience brought on by closed stores and schools and traffic issues. Residents’ opinions about police also suffered. Concerns about the police response relate to a perceived overreaction and specifically, use of military tactics, tear gas, rubber bullets and other tactics. Two-thirds of residents reported that the level of force used in the first few weeks was too much. The most common positive impacts from this event were an increased awareness about issues of racial tension, crime, and profiling. Twenty percent of the 389 residents interviewed participated directly in the protests. Yet, substantial numbers of residents raised concerns about the looting, riots, and vandalism that occurred

Sapping Features of the Colorado Plateau: a Comparative Planetary Geology Field Guide

This book is an attempt to determine geomorphic criteria to be used to distinguish between channels formed predominantly by sapping and seepage erosion and those formed principally by surface runoff processes. The geologic nature of the Colorado Plateau has resulted in geomorphic features that show similarities to some areas on Mars, especially certain valley networks within thick sandstone formations. Where spring sapping is an effective process, the valleys that develop are unique in terms of their morphology and network pattern

Ferguson\u27s Long Term Impact on Public Views about Police

Nearly one year after the shooting of Michael Brown and the unrest that followed in Ferguson, MO, African American residents\u27 perceptions about the legitimacy of police and trust and procedural justice show signs of recovery. These findings derive from a panel study of residents of hot spots of crime in St Louis County, MO, with three waves occurring in the two years preceding the incident, one immediately following the shooting and unrest, and a final set of interviews in summer 2015. Although the immediate effect of the police shooting and handling of unrest contributed to significant declines in trust in police and police legitimacy among African American residents, a preliminary analysis of more recent interviews suggest that confidence and trust are on the rise among these residents

Groundwater sapping valleys: Experimental studies, geological controls and implications to the interpretation of valley networks on Mars

An integrated approach using experimental laboratory models, field studies of terrestrial analogs, and remote studies of terrestrial field sites were applied to the goals of understanding the nature and morphology of valley networks formed by groundwater sapping. In spite of problems with scaling, the experimental studies provide valuable insights into concepts relating to the initiation, development, and evolution of valleys by groundwater sapping. These investigations are also aimed at developing geomorphic criteria for distinguishing valleys formed by surface runoff from those formed by groundwater sapping processes. Channels that were field classified as sapping vs. runoff were successfully distinguished using statistical analysis of their respective morphologies; therefore, it may be possible to use similar techniques to interpret channel genesis on Mars. The terrestrial and flume studies provide the ground truth dataset which can be used (and will be during the present year) to help interpret the genesis of valley networks on Mars