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Seamount trails created by mantle plumes are often used to establish absolute reference frames for plate motion. When plume drift is considered, changes in seamount trail direction and age progression cannot be attributed to plate motion change alone. Here, improvements to age‐progressive models of eleven Pacific hotspot chains are made independently of plate motion models. Our approach involves bathymetry processing to robustly predict a smooth, continuous hotspot path by connecting maxima in filtered seamount bathymetry, with across‐track uncertainties from seamount trail width and amplitude. Published ages from seamount samples are projected orthogonally onto these paths. We determine best‐fit models of age as functions of along‐track distance, giving continuous age‐progression models for each seamount chain with uncertainties in age and geometry. Different sources of paleolatitudes are examined by incorporating data from the magnetization of seamount drill‐core samples, paleo‐poles from marine magnetic anomaly skewness inversions, and paleo‐spin‐axes inferred from shifts of equatorial sediments. Improved paleolatitude models for the Hawaiian‐Emperor and Louisville chains are determined by combining these different types of data. Paleolatitude models are predicted for other chains during periods when sufficient amounts of paleo‐pole or paleo‐spin‐axis data are available. Analysis of the eleven Pacific seamount chains provide constraints for future plate and plume motion models. We analyze the temporal change in distance between coeval seamounts, reflecting relative drifts between the hotspots at different times in the past. The observed changes imply systematic relative hotspot drifts compatible with paleolatitude trends.

 

New bathymetric and gravity mapping, refined volume calculations and petrologic analyses show that the Hawaiian volcano P¯uh¯ahonu 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 largest Hawaiian volcano but also the largest known shield volcano. We considered four testable mechanisms to increase magma production, including 1) thinner lithosphere, 2) slower propagation rate, 3) more fertile source, and 4) hotter mantle. The first three of these have been ruled out. The lithosphere was old (∼88 Myrs) when P¯uh¯ahonu was formed, and thus, too thick and cold to allow for greater extents of partial melting. The propagation rate was relatively fast when it erupted (87 km/Myr), so this is another unlikely reason. Source fertility was Kea-like and no more fertile than for other much smaller NWHR volcanoes. A hotter mantle remains the best mechanism to produce the large magma volumes and is consistent with the high forsteritic olivine phenocryst compositions (up to 91.8%) and the calculated high percent of melting (24%). Thus, the gargantuan size of P¯uh¯ahonu reflects its high melting temperature, the highest reported for any Cenozoic basalt. A solitary wave within the Hawaiian plume is the probable cause of P¯uh¯ahonu’s higher melting temperature and the resulting increased volume flux given the absence of a more fertile source for P¯uh¯ahonu basalts, as found for many basalts from the Hawaiian Islands. 

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 steep learning curve with many pitfalls for beginners and experienced users alike. Reducing these pitfalls means changing the interface, which would break compatibility with thousands of existing scripts. With the latest GMT version 6, we solve this conundrum by introducing a new “modern mode” to complement the interface used in previous versions, which GMT 6 now calls “classic mode.” GMT 6 defaults to classic mode and thus is a recommended upgrade for all GMT 5 users. Nonetheless, new users should take advantage of modern mode to make shorter scripts, quickly access commonly used global data sets, and take full advantage of the new tools to draw subplots, place insets, and create animations.