Reprocessed and newly acquired seismic data provide new constraints on lithospheric flexure profiles beneath the Hawaiian Islands. We use these new observations and three-dimensional numerical models of lithospheric deformation combining elasticity, brittle failure, low-temperature plasticity (LTP) and high-temperature creep deformation mechanisms to constrain the thermal structure and rheology of the oceanic lithosphere lithosphere. When simulating normal oceanic lithospheric conditions with experimentally-derived LTP flow laws, the lithosphere flexes with too little amplitude and over too large a wavelength compared to observations. This result supports prior studies which call on the need to (1) adjust the LTP flow laws or, alternatively, to (2) account for magma-assisted flexural weakening of the lithosphere. Here, models that explore reductions in the activation energy of LTP are able to explain the observations of flexure with a smaller reduction than previously suggested. Models that explore elevated temperatures attributed to hotspot magmatism localized beneath the island edifices also produce close fits to the observed flexural profiles. Although the two factors cannot be distinguished based on fits to the flexure profiles, magma-assisted flexural weakening is supported by recent studies of geothermobarometry of pyroxenite xenoliths from O‘ahu, seismic structure and patterns of seismicity beneath the Hawaiian chain. If magma-assisted flexure is a common phenomenon at other ocean islands and seamounts, it could explain global trends in effective elastic plate thickness at those settings as well as at subduction zones and fracture zones.

-The Generic Mapping Tools (GMT) is a well-known set of software originally developed for geosciences, allowing scientists in climate and solid earth disciplines to routinely create publish-ready maps and graphics. However, GMT users rarely make animations despite their undeniable benefit for understanding and teaching dynamical processes. As reading habits shift from print to digital, capitalizing on animations for illustrating scientific concepts is more accessible than ever. In the latest GMT version (6.5) we have added and refined the moving-making modules, alleviating the time-consuming steps that would hinder GMT users from making such animations. In this paper we will explain how GMT ”movie” works then provide six representative examples, from basic to more advanced, to show some of its key features. We hope our presentation will encourage the masses to routinely create animations for their publications.  See videos at: https://youtube.com/playlist?list=PL3GHXjKa-p6VdPql5aReLQZeQDJgWDAY-

To date, approximately 20% of the ocean floor has been surveyed by ships at a spatial resolution of 400 m or better. The remaining 80% has depth predicted from satellite altimeter-derived gravity measurements at a relatively low resolution. There are many remote ocean areas in the southern hemisphere that will not be completely mapped at 400 m resolution during this decade. This study is focused on the development of synthetic bathymetry to fill the gaps. There are two types of seafloor features that are not typically well resolved by satellite gravity: abyssal hills and small seamounts (< 2.5 km tall). We generate synthetic realizations of abyssal hills by combining the measured statistical properties of mapped abyssal hills with regional geology including fossil spreading rate/orientation, rms height from satellite gravity, and sediment thickness. With recent improvements in accuracy and resolution, It is now possible to detect all seamounts taller than about 800 m in satellite-derived gravity and their location can be determined to an accuracy of better than 1 km. However, the width of the gravity anomaly is much greater than the actual width of the seamount so the seamount predicted from gravity will underestimate the true seamount height and overestimate its base dimension. In this study we use the amplitude of the vertical gravity gradient (VGG) to estimate the mass of the seamount and then use their characteristic shape, based on well surveyed seamounts, to replace the smooth predicted seamount with a seamount having a more realistic shape.

Seamounts are isolated elevations in the seafloor with circular or elliptical plan, comparatively steep slopes, and relatively small summit area (Menard, 1964). The vertical gravity gradient (VGG), which is the curvature of the ocean surface topography derived from satellite altimeter measurements, has been used to map the global distribution of seamounts (Kim & Wessel, 2011). We used the latest grid of VGG to update and refine the global seamount catalog; we identified 10,796 new seamounts, expanding the catalog by 1/3. 739 well-surveyed seamounts, having heights ranging from 421 m to 2500 m, were then used to estimate the typical radially-symmetric seamount morphology. First, an Empirical Orthogonal Function (EOF) analysis was used to demonstrate that these small seamounts have a basal radius that is linearly related to their height – their shapes are scale invariant. Two methods were then used to compute this characteristic base to height ratio: an average Gaussian fit to the stack of all profiles and an individual Gaussian fit for each seamount in the sample. The first method combined the radial normalized height data from all 739 seamounts to form median and median-absolute deviation. These data were fit by a 3-parameter Gaussian model that explained 99.82% of the variance. The second method used the Gaussian function to individually model each seamount in the sample and further establish the Gaussian model. Using this characteristic Gaussian shape we show that VGG can be used to estimate the height of small seamounts to an accuracy of ~270 m.