Spatial Morphometric Analysis Using Shape-Changing Rigid-Body Chains

Morphometry is the quantitative comparison of shapes, primarily curves. As an alternate to classical methods of spatial morphometry, this work investigates a kinematic synthesis methodology for designing a spatial chain of rigid-bodies to match arbitrary spatial curves. The goal is to find a single set of spatial bodies that can be moved to approximately align with any given set of spatial curves. Previous rigid-body shape-change morphometry work focused on mechanisms composed of rigid planar links connected by prismatic and revolute joints to approximate planar curves. Open space curves are the current focus of the research. The primary advantage of this method is its capacity to describe the difference in space curves with a limited number of parameters.https://ecommons.udayton.edu/stander_posters/2395/thumbnail.jp

Subannual temporal variation in faunal distributions at the TAG hydrothermal mound (26°N, Mid-Atlantic Ridge)

This paper evaluates the dynamics of two faunal assemblages colonizing high- and low-temperature habitats of the TAG hydrothermal mound on the Mid-Atlantic Ridge. Timelapse video and photographic transects were used to monitor changes in shrimp and anemone populations from June 1994 to March 1995. During this period, holes were drilled in the vicinity of the target populations by the Ocean Drilling Program (ODP). The a priori expectation of a rapid redistribution of motile alvinocaridid shrimp to occupy the optimal thermal and chemical habitat in response to changes in the pattern of hydrothermal activity was met by the observation of an increase in hydrothermal activity and shrimp population density at the site where a timelapse video system was deployed. The importance of hydrothermal activity as a control on the distribution of vent shrimp is suggested by tidal variations in the distribution of shrimp on a minidiffuser chimney. Sediment deposition during ODP drilling resulted in a temporary disturbance of the shrimp occupying the flat part of the mound surface seen by the timelapse video. In contrast to the changes observed in shrimp distribution, little change was observed in the distribution of anemones across the mound in two photographic transects 10 months apart, with the exception of a localized disturbance where anemones were buried by sediment around an ODP hole. Differences in the response of the shrimp and anemones to changes in the hydrothermal system may result from differences in their motility and rates of biological activity, or reflect a lower trophic position in the case of the shrimp.</p

Development and evolution of detachment faulting along 50 km of the Mid-Atlantic Ridge near 16.5°N

A multifaceted study of the slow spreading Mid-Atlantic Ridge (MAR) at 16.5°N provides new insights into detachment faulting and its evolution through time. The survey included regional multibeam bathymetry mapping, high-resolution mapping using AUV Sentry, seafloor imaging using the TowCam system, and an extensive rock-dredging program. At different times, detachment faulting was active along ∼50 km of the western flank of the study area, and may have dominated spreading on that flank for the last 5 Ma. Detachment morphologies vary and include a classic corrugated massif, noncorrugated massifs, and back-tilted ridges marking detachment breakaways. High-resolution Sentry data reveal a new detachment morphology; a low-angle, irregular surface in the regional bathymetry is shown to be a finely corrugated detachment surface (corrugation wavelength of only tens of meters and relief of just a few meters). Multiscale corrugations are observed 2–3 km from the detachment breakaway suggesting that they formed in the brittle layer, perhaps by anastomosing faults. The thin wedge of hanging wall lavas that covers a low-angle (6°) detachment footwall near its termination are intensely faulted and fissured; this deformation may be enhanced by the low angle of the emerging footwall. Active detachment faulting currently is limited to the western side of the rift valley. Nonetheless, detachment fault morphologies also are present over a large portion of the eastern flank on crust >2 Ma, indicating that within the last 5 Ma parts of the ridge axis have experienced periods of two-sided detachment faulting