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The Yellowstone hotspot resulted from interaction of a mantle plume with the overriding North America plate highly modifying the lithosphere by magmatic-tectonic processes and producing the 17 Ma Yellowstone-Snake River Plain (YSRP) volcanic system. The accessibility of the YSRP has allowed largescale geophysical experiments to seismically image the hotspot and to evaluate its kinematic and dynamic properties using geodetic measurements. Tomography reveals a Yellowstone crustal magma body with 8-15% melt that is fed by an upper-mantle plume extending from 80 km to 660 km deep and tilting 60º west. Contemporary deformation of the Yellowstone caldera is dominated by SW-extension at up to ~3 mm/yr, a fourth of the total Basin-Range opening rate, but with superimposed volcanic uplift and subsidence at decade scales, averaging ~2 cm/yr and unprecedented caldera uplift from 2004-2008 at up to 7 cm/yr. Convection models reveal eastward upper-mantle flow beneath Yellowstone at relatively high rates of 5 cm/yr and opposite in direction to the overriding N. American Plate. This strong flow deflects the ascending plume melt into a tilted configuration, i.e., the plume is caught in a mantle "wind". Dynamic models of the Yellowstone plume revealed relatively low excess temperatures, up to 120°K, with up to 1.5% melt, properties consistent with a weak buoyancy flux of ~0.25 Mg/s. The flux is several times smaller than for oceanic plumes, but it produced a ~600-km wide topographic ~300-m high swell. Employing the plume-geometry we extrapolated the location of the Yellowstone mantle-source southwestward to its initial position at 17 million years beneath eastern Oregon and the southern edge of the LIP Columbia Plateau basalt field suggesting a common origin. Our model suggests that the original plume head rose vertically behind the subducting Juan de Fuca plate, but at ~12 Ma it lost the protection of the subducting plate and encountered cooler, thicker continental lithosphere and became affected by the eastward upper-mantle flow. Regionally, excess gravitation potential energy of the swell drives the SW motion of the YSRP lithosphere that becomes part of a general clockwise rotation pattern of intraplate western U.S. tectonism. Our models thus demonstrate that plume-plate processes of the YSRP have "continentalized" oceanic lithosphere enhancing intraplate extension and highly modifying topography, deep into the continental interior. Our results demonstrate that the dynamic properties of the Yellowstone hotspot deserved its recognition as a "window into the Earth's interior". JVGR

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SUMMARY We present results of a non‐linear teleseismic P‐wave traveltime tomography in Ireland. Relative traveltime residuals are calculated from the data set of the Irish Seismological Lithospheric Experiment (ISLE 2002/3) and permanent stations onshore Ireland. At each of the 28 station sites, a local crustal 1‐D P‐wave velocity (vP) model is determined because the 3‐D crustal vP structure of Ireland is well known. These 1‐D models are used for a traveltime correction for crustal effects. The corrected residuals indicate two large‐scale traveltime anomalies of low amplitude: a negative traveltime anomaly in the western part of Ireland and a positive anomaly in the eastern part of the country. The subsequent traveltime tomography is calculated using an iterative non‐linear inversion using a variable parametrization and 3‐D ray tracing. Our inversion result contains a low P‐wave velocity (vP) zone underneath central Ireland, at 31–120 km depth. The amplitudes of the low velocity zone reach up to −2.5 per cent vP at 31–60 km depth, but decrease to −0.5 to −1 per cent vP at 120–150 km depth. Reconstruction tests confirm that large anomalies in our model are well resolved, although the resolution decreases towards the edges of the model. We infer that the low velocity zone underneath central Ireland is related to lithospheric thinning towards the north, which was determined by a previous S‐receiver function study. This anomaly is interpreted as presumably ancient or even recent mantle upwelling, related to the spreading of the Iceland plume head.

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S U M M A R YTeleseismic P-wave tomography has revealed a columnar low-velocity anomaly in the upper mantle below the volcanic Eifel region in western Germany extending to at least 400 km depth.Here we explore whether a geodynamically consistent model of a mantle plume can explain the observed traveltime residuals. We use a 3-D mantle convection code with temperature and pressure-dependent viscosity to generate a suite of model plumes that rise from the transition zone and spread below a stationary or drifting lithospheric plate. We use ray tracing to calculate synthetic travel times and vary the plume location, radius, temperature and the rate and direction of plate motion in order to fit the observed travel times. Our results show a fair correlation between synthetic and observed traveltime residuals. The presence of additional structures in the lithosphere and upper mantle of the Eifel region that are not covered by a simple plume model prevents a perfect fit of the observed seismological data and may bias to some degree the derived plume parameters. The traveltime anomalies are mainly caused by the plume stem with smaller contributions from the plume head. Models with and without an axisymetric plume head below the lithosphere fit the data almost equally well and we conclude that the absence of a plume head in tomographic images does not rule out its existence. In the best-fitting model the plume stem has a radius of 60 km and rises about 50 km to the SW of the quaternary volcanic field below a lithosphere that this slowly moving in the NNE direction. The temperature of the plume and its flux cannot be constrained tightly from our model results, but combining them with other constraints we estimate an excess temperature of ∼200 • C and a buoyancy flux of 500-1000 kg s −1 .

The Cenozoic volcanism in the French Massif Central region is fed by an upper mantle plume, which was revealed by teleseismic tomography about 10 years ago. This contribution reviews earlier studies and applies a new method to image the crust and upper mantle in the region. Since teleseismic tomography alone has only moderate ability to resolve crustal structures, we perform an integrated study by a joint teleseismic-gravimetric inversion to investigate the gross crustal imprints of the Massif Central. We use a 3-dimensional joint inversion code, which allows a variable model parameterisation, and 3D ray tracing to perform an iterative inversion. Travel time residuals are corrected for Moho topography and sedimentary influences to avoid mapping of known crustal structure into the mantle.Our study finds a prominent low-velocity structure in the upper mantle, which is interpreted as the thermal signature of the Massif Central plume. With a modelled diameter of about 100-120 km it reaches down to at least 330 km depth. The average determined seismic P-wave velocity contrast is -0.6% to -1.0% in the shallow asthenospheric mantle and deeper upper mantle. We found two low-velocity channels in the crustal layer beneath the Cantal/Monte Dore and south of the Devès volcanic fields. A zone of mainly high density and increased seismic velocity is determined in the crust south of the Limagne Graben between the two volcanic fields. Furthermore the Massif Central is characterised by increased seismic scattering in the lithosphere as found by studying the teleseismic P-wave coda. We interpret the detected high-velocity/high-density body and the lithospheric scatterers as cooled magmatic intrusions, produced during the Cenozoic volcanism.