Paul Wessel

University of Hawaiʻi at Mānoa | UH Manoa · Department of Earth Sciences

Seamounts are volcanic constructs that litter the seafloor. They are important for understanding numerous aspects of marine science, such as plate tectonics, the volcanic melt budget, oceanic circulation, tsunami wave diffraction, tidal energy dissipation, and mass wasting. Geometrically, seamounts come in many sizes and shapes, and for the purpose...

This chapter provides an overview over the current spectrum of free and open source licensed geospatial software tools and communities. The number of available open source geospatial tools continues to grow and diversify, while new fields of application emerge. This chapter presents a selection of well-established free and open source software (FO...

We used the latest vertical gravity gradient maps to update and refine a global seamount 12 catalog, finding 10,796 new seamounts. 13 • Smaller seamounts (< 2500 m tall) having good bathymetry coverage (739) were modeled 14 with a radially symmetric Gaussian function. 15 • Two modeling approaches show that smaller seamounts have a sigma to height r...

To date, ∼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...

Marine geophysical exchange files for R/V Kilo Moana: 2002 to 2018 includes 328 geophysical archive files spanning km0201, the vessel's very first expedition, through km1812, the last survey included in this data synthesis, all of which are freely available online at https://doi.org/10.5281/zenodo.4699568.

New bathymetric and gravity mapping, refined volume calculations and petrologic analyses show that the Hawaiian volcano Pūhāhonu is the largest and hottest shield volcano on Earth. This ∼12.5-14.1 Ma volcano in the northwest Hawaiian Ridge (NWHR) is twice the size of Mauna Loa volcano (148 ± 29 vs. 74.0×103km3), which was assumed to be not only the...

We examine the rheology and thermal structure of the oceanic lithosphere, expressed in situ by plate flexure beneath the Hawaiian Ridge, where volcanoes of variable sizes have loaded seafloor of approximately the same age, and thus where the lithosphere is expected to have had an approximately uniform age-dependent thermal structure at the time of...

A geophysical survey of the Ellice Basin, located in the south equatorial Pacific between the Ontong Java and Manihiki plateaus, revealed evidence for an extinct seafloor spreading system between the Pacific Plate and the Manihiki Plate. The spreading occurred during the Cretaceous Normal Superchron, the longest normal period of magnetic polarity f...

An updated global bathymetry and topography grid is presented using a spatial sampling interval of 15 arc seconds. The bathymetry is produced using a combination of shipboard soundings and depths predicted using satellite altimetry. New data consists of >33.6 million multi and singlebeam measurements collated by several institutions, namely, the Na...

The Generic Mapping Tools (GMT) software is ubiquitous in the Earth and Ocean sciences. As a cross‐platform tool producing high quality maps and figures, it is used by tens of thousands of scientists around the world. The basic syntax of GMT scripts has evolved very slowly since the 1990s, despite the fact that GMT is generally perceived to have a...

Preserving costly marine geophysical trackline data is of paramount importance but variability in priorities, funding, personnel, and technology impact our data archival capacity. We have addressed one crucial facet of this dilemma by devising an open source approach to merge and reduce underway geophysical data and to generate marine geophysical a...

A new global bathymetry and topography grid (SRTM15_PLUS) is presented based on an updated compilation of ship soundings as well as depths predicted from satellite derived free-air gravity anomalies. The National Geospatial-Intelligence Agency provided 19 million, averaged soundings (15 arcsecond averages) in areas not covered by our previous 2014...

The emplacement of the world’s single largest oceanic plateau Ontong Java Nui, composed of present day Ontong Java, Manihiki and Hikurangi plateaus and other now subducted fragments, was abruptly followed by the long normal magnetic period known as the Cretaceous Normal Superchron (CNS, 121-83 Ma). A large component of oceanic crust in the Pacific...

The alignment and age progression of volcanoes produced as a tectonic plate moves over a mantle plume can be used to reconstruct both the direction and rate of past plate motion assuming the plume remains in a fixed location. New ⁴⁰Ar/³⁹Ar dates for lavas from 15 volcanoes spanning the entire length (~2800 km) of the Northwest Hawaiian Ridge (NWHR)...

Although partial melt in the asthenosphere is important geodynamically, geophysical constraints on its abundance remain ambiguous. We use a database of seamounts detected using satellite altimetry to constrain the temporal history of erupted asthenospheric melt. We find that intraplate volcanism on young seafloor (<60 Ma) equates to a ~20 m thick l...

R/V Kilo Moana expedition KM1609 to the Ellice Basin set out to test the hypothesis of the proposed Ontong Java-Manihiki-Hikurangi breakup and subsequent formation of the Ellice Basin during the Cretaceous Normal Superchron. In addition to swath mapping, dredging, and sub-bottom profiling, we deployed a Geometrics G-882 cesium-vapor marine magnetom...

The GMT/MATLAB toolbox is a basic interface between MATLAB® (or Octave) and GMT, the Generic Mapping Tools, which allows MATLAB users full access to all GMT modules. Data may be passed between the two programs using intermediate MATLAB structures that organize the metadata needed; these are produced when GMT modules are run. In addition, standard M...

We present a method for interpolation of sparse two-dimensional vector data. The method is based on the Green's functions of an elastic body subjected to in-plane forces. This approach ensures elastic coupling between the two components of the interpolation. Users may adjust the coupling by varying Poisson's ratio. Smoothing can be achieved by igno...

Relative plate motions provide high-resolution descriptions of motions of plates relative to other plates. Yet geodynamically, motions of plates relative to the mantle are required since such motions can be attributed to forces (e.g., slab pull, ridge push) acting upon the plates. Various reference frames have been proposed, such as the hotspot ref...

Animations of ridge-spotting was performed using the Generic Mapping Tools and show how the reconstructed ridges migrate over time. For each time step, locations with crustal age within the 0.5 Myr time window were reconstructed using an absolute plate motion model and overlaid on the map in present coordinates. All movies are in the MP4 format. M...

Modern processing of satellite altimetry for use in marine gravimetry involves computing the along-track slopes of observed sea-surface heights, projecting them into east-west and north-south deflection of the vertical grids, and using Laplace's equation to algebraically obtain a grid of the vertical gravity gradient (VGG). The VGG grid is then int...

In the original paper, Equation A3 in the Appendix has a sign error which is corrected here. Thanks to Arne Døssing who helped out on this issue when preparing the article "Gravity inversion predicts the nature of the Amundsen Basin and its continental borderlands near Greenland" (DOI: 10.1016/j.epsl.2014.10.011)

Observations of the temporal variations in the volume flux of a plume can provide useful constraints on geodynamic models of plumes and plume-plate interactions. Furthermore, they can be compared with observations at other plumes and may be analysed further to understand the nature and cause of the variations. The volume plume flux is typically der...

Seamounts are ubiquitous manifestations of underwater volcanism that rise above the surrounding ocean floor by more than a few hundred or thousand meters. Any temporal and spatial variations of the underwater volcanic and tectonic processes that formed seamounts can primarily be understood through their geometric characterization and spatial distri...

Plate tectonics, our major paradigm for how the Earth works, was established in the 1960ies following decades of observational research that culminated in key discoveries such as geomagnetic reversals, mid-ocean ridges, transform faults, and seafloor spreading. Plate tectonics is the surface manifestation of mantle convection, but the large contras...

Oceanic fracture zone traces are widely used in studies of seafloor morphology and plate kinematics. Satellite altimetry missions have resulted in high-resolution gravity maps in which all major fracture zones and other tectonic fabric can be identified, and numerous scientists have digitized such lineaments. We have initiated a community effort to...

Plate tectonic motions are commonly considered to be driven by slab pull at subduction zones and ridge push at mid-ocean ridges, with motion punctuated by plumes of hot material rising from the lower mantle(1,2). Within this model, the geometry and location of mid-ocean ridges are considered to be independent of lower-mantle dynamics, such as deepl...

Numerous regional plate reorganizations and the coeval ages of the Hawaiian Emperor bend (HEB) and Louisville bend of 50-47 Ma have been interpreted as a possible global tectonic plate reorganization at ~chron 21 (47.9 Ma). Yet for a truly global event we would expect a contemporaneous change in Africa absolute plate motion (APM) reflected by physi...

A substantial portion of the Pacifi c basin is composed of seafl oor formed during the Cretaceous Normal Superchron (CNS). Because this region lacks the magnetic lineations typically required to constrain tectonic reconstructions, we employ additional methods for interpreting CNS Pacifi c history, involving seafl oor fabric, basement paleolatitudes...

The Papahānaumokuākea Marine National Monument (PMNM) is a 362,073 km2 conservation area encompassing islands and seamounts with prodigious diversity of size and morphologies formed by Hawaiian hotspot volcanism 7-31 Myr ago. During the winter and spring of 2014, we collaborated with the Schmidt Ocean Institute to conduct a detailed bathymetric map...

In this study, we aim to understand the variability in eruption volume estimates derived from field studies of pyroclastic deposits. We distributed paper maps of the 1959 Kīlauea Iki tephra to 101 volcanologists worldwide, who produced hand-drawn isopachs. Across the returned maps, uncertainty in isopach areas is 7 % across the well-sampled deposit...

Magnetic anomaly identifications underpin plate tectonic reconstructions and form the primary data set from which the age of the oceanic lithosphere and seafloor spreading regimes in the ocean basins can be determined. Although these identifications are an invaluable resource, their usefulness to the wider scientific community has been limited due...

When estimating the magnitude of explosive eruptions from their deposits, individuals make three sets of critical choices with respect to input data: the spacing of sampling sites, the selection of contour intervals to constrain the field measurements, and the hand contouring of thickness/isomass data, respectively. Volcanologists make subjective c...

Generic Mapping Tools (GMT) is an open-source software package for the analysis and display of geoscience data, helping scientists to analyze, interpolate, filter, manipulate, project, and plot time series and gridded data sets. The GMT toolbox includes about 80 core and 40 supplemental program modules sharing a common set of command options, file...

More than 60% of the Earth's land and shallow marine areas are covered by > 2 km of sediments and sedimentary rocks, with the thickest accumulations on rifted continental margins (Figure 1). Free-air marine gravity anomalies derived from Geosat and ERS-1 satellite altimetry (Fairhead et al., 2001; Sandwell and Smith, 2009; Andersen et al., 2009) ou...

We have discovered evidence of a previously unrecognized, large-scale rotation of the Ontong Java Plateau (OJP) recorded in its basement palaeolatitudes. When palaeolatitude differences computed among Ocean Drilling Program Sites 807 and 1183-1187 are plotted versus their present-day site latitude differences, a systematic 2:1 slope bias is evident...

The Hawaiian Ridge portion of the Hawaiian-Emperor Chain, the classic example of a mantle plume produced linear island chain, is 6000 km in length, active for 80 Myr, and tectonically simple. Despite its importance to our understanding of mantle plumes and Cenozoic plate motion, there are large data gaps for the age and geochemistry of lavas from v...

We announce the completion of 5,230 errata correction tables which remove extreme, obvious errors from the National Geophysical Data Center's marine geophysical trackline archive. Along with a range of error types correctable using along-track analysis, we determined that ˜62% of gravity surveys omit raw measurements and that ˜89% of magnetic anoma...

The Easter Seamount Chain and Nazca Ridge are two of the most conspicuous volcanic features on the Nazca plate. Many questions about their nature and origin have remained unresolved because of a lack of geochronological and geochemical data for large portions of both chains. New 40Ar−39Ar incremental heating age determinations for dredged rocks fro...

The Taylor (2006) hypothesis suggesting a common origin for the Ontong Java, Manihiki, and Hikurangi large igneous provinces provides an opportunity for a quantitative reconstruction and reassessment of the Ontong Java–Louisville hotspot connection. Our plate tectonic reconstructions of the three plateaus into Ontong Java Nui, or greater Ontong Jav...

We present a global community data set of fracture zones (FZs), discordant zones, propagating ridges, V-shaped structures and extinct ridges, digitized from vertical gravity gradient (VGG) maps. We use a new semi-automatic FZ tracking program to test the precision of our hand-digitized traces and find a Mean Absolute Deviation of less than 3.4 km f...

Using new data set of seamount ages on the African plate, a model of motion of the African plate relative to the African hotspots are calculated by the Polygonal Finite Rotation Method; PFRM (Harada and Hamano, 2000). The new motion of the African plate has more abrupt change at about 50Ma than the previous models of the African plate mainly due to...

Statistical analysis shows that there is an unusually high incidence of recent (<10 Ma), intraplate volcanism over asthenosphere that is predicted to be rapidly shearing. This result is heavily influenced by the large number of small seamounts west of the Eastern Pacific Rise, and small-volume basaltic volcanism throughout the Western United States...

The Hawaii-Emperor Bend (HEB) has become a lightening rod for studies of absolute plate motion (APM). Initially seen as the clearest evidence for an APM change over an approximately stationary hotspot, recent studies have suggested that the HEB represents no change in APM motion at all. Instead, it has been proposed that there was a rapid retardati...

We have discovered an apparent rotational property inherent in Ontong Java Plateau’s basement paleolatitudes. The pattern is evident when comparing differences in ODP paleolatitudes to differences in their corresponding drill site latitudes. When latitude differences computed among sites 807 and 1183-1187 are plotted against their respective paleol...

GMT is a well-established, open source collection of tools for manipulating and plotting geographic and Cartesian data sets (including filtering, trend fitting, gridding, spatial analysis, mapping, etc.). The software produces high-quality PostScript illustrations ranging from simple x-y plots via contour maps to artificially illuminated surfaces a...

Over the past 15 years, software for processing interferometric synthetic aperture radar (InSAR) data into maps of surface deformation has been developed and refined. The InSAR technique is commonly used to investigate deformation associated with earthquakes, volcanoes, withdrawal of crustal fluids, and coherent ice motions [Massonnet and Feigl, 19...

Recent revisions to the satellite-derived vertical gravity gradient (VGG) data reveal more detail of the ocean bottom and have allowed us to develop a non-linear inversion method to detect seamounts in VGG data. We approximate VGG anomalies over seamounts as sums of individual, partially overlapping, elliptical polynomial functions, which allows us...

Most of Earth's volcanism occurs at plate boundaries, in association with subduction or rifting. A few high-volume volcanic fields are observed both at plate boundaries and within plates, fed by plumes upwelling from the deep mantle. The remaining volcanism is observed away from plate boundaries. It is typically basaltic, effusive and low volume, o...

We examine how bathymetric mapping coverage varies with distance from the coastline, here a proxy for the effort involved in collecting the data. Distances to the nearest coastline were evaluated on a 1′ × 1′ global grid. We evaluate the density of marine survey track lines, which falls off with increasing distance from the coastline and drops off...

GMTSAR is an open source (GNU General Public License) InSAR processing system designed for users familiar with Generic Mapping Tools (GMT). The code is written in C and will compile on any computer where GMT and NETCDF are installed. The system has three main components: 1) a preprocessor for each satellite data type (e.g., ERS, Envisat, and ALOS)...

Convection in the Earth's mantle, manifested at the surface as plate tectonics, generates the majority of Earth's volcanism via rifting and subduction. Intraplate volcanism, occurring away from plate boundaries, has not been attributed to global-scale convection, but instead to a variety of localized processes such as upwelling plumes, lithospheric...

A review of Earth's most signifi cant intraplate Cenozoic hotspots with regard to variations in magmatic productivity through time indicates periodicities with a dominant period of ~10 m.y. and a secondary period of ~5 m.y. It is unlikely that the observed global variations in magmatic productivity can be explained by differences in lithospheric th...

With low-tech equipment, variable levels of planning, and plenty of courage, late nineteenth and early twentieth century explorers mesmerized the world with daring attempts to reach Earth’s geographic poles. The one hundredth anniversary of Robert Peary’s controversial North Pole claim was in April 2009, and the centennial of Roald Amundsen’s undis...

The lithospheric response to seamounts and ocean islands has been successfully described by deformation of an elastic plate induced by a given volcanic load. If the shape and mass of a seamount are known, the lithospheric flexure due to the seamount is determined by the thickness of an elastic plate, Te, which depends on the load density and the ag...

Electron backscatter diffraction analysis of dendritic clinopyroxene (cpx) forming in rapidly cooled basalt reveals two features that are unexpected for phases growing from a liquid: (1) helical growth about {010}(cpx), the crystallographic b-axis, with incremental rotation (up to 0.4 degrees mu m(-1)) within branch segments and large rotational ju...

I present a new set of tools for detection of intersections among tracks in 2-D Cartesian or geographic coordinates. These tools allow for evaluation of crossover errors at intersections, analysis of such crossover errors to determine appropriate linear models of systematic corrections for each track, and application of these corrections and furthe...

Seamounts are active or extinct undersea volcanoes with heights exceeding ~ 100 m. They represent a small but significant fraction of the volcanic extrusive budget for oceanic seafloor and their distribution gives information about spatial and temporal variations in intraplate volcanic activity. In addition, they sustain important ecological commun...

Wessel et al. (2010) highlight the need for a systematic mapping of seamounts in ocean basins. They estimate that 100,000 or 90% of the seamounts greater than 1-km tall are unobserved by either ship soundings or satellite gravity. There are two reasons why most of these relatively large, predicted seamounts remain uncharted. First, satellite-derive...

Plate kinematic models derive from the detailed identifications of conjugate magnetic isochron picks and fracture zones (FZ). These data form the foundation of relative marine plate tectonic reconstructions and codify our understanding of Earth's surface evolution since the Mesozoic. Furthermore, FZ traces have extensive uses in other geophysical i...

The classic view of linear island chains as volcanic expressions of interactions between changing plate tectonic motions and fixed mantle plumes has come under renewed scrutiny. In particular, observed paleolatitudes from the Emperor seamounts imply that the Hawaii hotspot was >5–15° further north during formation of these seamounts and that rapid...

I have examined over 1500 historical tsunami travel-time records for 127 tsunamigenic earthquakes that occurred in the Pacific and Indian Oceans. After subjecting the observations to simple tests to rule out gross errors I compare the remaining reports to simple travel-time predictions using Huygens method and the long-wave approximation, thus simu...

A useful approach to data interpolation is to determine the Green's function for the interpolation operator and construct the interpolation from the super-positioning of suitably scaled Green's functions located at the data constraints. Such Green's functions have been determined for Cartesian splines in 1-, 2-, and 3-D, including regularized splin...