Present-day plate motions (original) (raw)
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Supplemental material: Plate velocities in the hotspot reference frame
Geological Society of America eBooks, 2007
We have made a table of 57 hotspots, giving the track azimuths of their present motions and track rates where there was age control. This electronic supplement (with 301 references) gives the supporting data for each entry in this table and has a discussion of the probable errors in azimuth/rate for each entry. It also contains a discussion of 'hotspot-like-features' considered not to show plate motion and omitted from the table. DISCUSSION OF EACH TRACK Eurasian Plate Eifel (50.2°N, 6.7°E) w= 1 az= 082° ± 8° rate= 12 ± 2 mm/yr This is the best defined track on the Eurasian plate. Also, seismic tomographic studies have shown a low velocity column beneath Eifel extending down to at least 400 km (e.g., Wüllner et al., 2006). We used the locations of volcanics from Lippolt (1983) to determine an azimuth (082°) and have estimated its uncertainty to be ± 8°. This track has a moderately well determined rate. Duncan et al. (1972) found a (poorly determined) rate of 23 mm/yr based on early published K-Ar data and stratigraphic estimates of the ages of different volcanics. (Most of their references were published between 1960 and 1971, although some were as early as the 1930's.) There was a large effort to date these volcanics by the K-Ar method in the late 70's and early 80's that is
Journal of Geophysical Research, 2012
1] We defined a new global moving hot spot reference frame (GMHRF), using a comprehensive set of radiometric dates from arguably the best-studied hot spot tracks, refined plate circuit reconstructions, a new plate polygon model, and an iterative approach for estimating hot spot motions from numerical models of whole mantle convection and advection of plume conduits in the mantle flow that ensures their consistency with surface plate motions. Our results show that with the appropriate choice of a chain of relative motion linking the Pacific plate to the plates of the Indo-Atlantic hemisphere, the observed geometries and ages of the Pacific and Indo-Atlantic hot spot tracks were accurately reproduced by a combination of absolute plate motion and hot spot drift back to the Late Cretaceous ($80 Ma). Similarly good fits were observed for Indo-Atlantic tracks for earlier time (to 130Ma).Incontrast,attemptstodefineafixedhotspotframeresultedinunacceptablemisfitsfortheLateCretaceoustoPaleogene(80−50Ma),highlightingthesignificanceofrelativemotionbetweenthePacificandIndo−Atlantichotspotsduringthisperiod.AcomparisonofabsolutereconstructionsusingtheGMHRFandthemostrecentglobalpaleomagneticframerevealssubstantialamountsoftruepolarwanderatratesvaryingbetween130 Ma). In contrast, attempts to define a fixed hot spot frame resulted in unacceptable misfits for the Late Cretaceous to Paleogene (80-50 Ma), highlighting the significance of relative motion between the Pacific and Indo-Atlantic hot spots during this period. A comparison of absolute reconstructions using the GMHRF and the most recent global paleomagnetic frame reveals substantial amounts of true polar wander at rates varying between 130Ma).Incontrast,attemptstodefineafixedhotspotframeresultedinunacceptablemisfitsfortheLateCretaceoustoPaleogene(80−50Ma),highlightingthesignificanceofrelativemotionbetweenthePacificandIndo−Atlantichotspotsduringthisperiod.AcomparisonofabsolutereconstructionsusingtheGMHRFandthemostrecentglobalpaleomagneticframerevealssubstantialamountsoftruepolarwanderatratesvaryingbetween0.1 /Ma and 1 /Ma. Two intriguing, nearly equal and antipodal rotations of the Earth relative to its spin axis are suggested for the 90-60 Ma and 60-40 Ma intervals ($9 at a 0.3-0.5 /Ma rate); these predictions have yet to be tested by geodynamic models.
Plate velocities in the hotspot reference frame
Special Paper 430: Plates, Plumes and Planetary Processes, 2007
We present a table of 57 hotspots distributed on all major plates with a short discussion of the 'present-day' (average over most recent ~5 Ma) direction and velocity for each hotspot track, with estimated errors. An electronic supplement has a discussion of each track and references to the data sources. Using the entries in Table 1, we found Pacific plate motion is a rotation about a pole at 59.33°N, 85.10°W with a rate that gives a velocity at the pole's 'equator' of 89.20 mm/yr (=-0.8029 °/Ma). The errors in this pole/rate are of the order ±2°N, ±4°W, ±3 mm/yr. The motions of other plates are then determined by NUVEL-1A. The large number of close, many very short, tracks in the Pacific superswell region precludes all hotspots being rooted near the core-mantle boundary. In general, we think asthenosphere is hotter than mantle just below it (in a potential temperature sense). Asthenosphere is very hotbrought up from the core-mantle boundary by plumes. Mantle is cooled by downgoing slabs, and a convective stability is established whereby mantle rises only at plumes and sinks only at trenches. We propose that this normal mantle geotherm is overwhelmed by much-larger-thanaverage mantle upwelling in superswell areas, making many short-lived instabilities in the upper mantle. Because soft asthenosphere so decouples plates from mantle below, instabilities in the 2 upper mantle (perhaps even above the 660-km discontinuity) are relatively 'fixed' in comparison to plate motions. With the mantle velocity contribution being minor, tracks are parallel to and have rates set by plate velocities.
Discussion of Plate velocities in the hotspot reference frame by
A difficulty arises in the plum-pudding plume model (Morgan and Phipps Morgan, this volume; Yamamoto et al., this volume) with regard to Pt-Os isotope systematics. The Os/Os ratios in the MORB-source mantle, as indicated by the isotopic compositions of abyssal peridotites (Os/Os = 0.119830 0.119838), are generally lower than in intraplate volcanic rocks (Hawaiian picrites and Gorgona komatiites; Os/Os = 0.119831 0.119850). In standard plume models, where MORB and intraplate volcanic rocks are derived from distinct isolated reservoirs, the isotopic differences are explained by the addition of approximately 0.5 weight percent outer-core material (Os/Os = 0.119870) to a plume (Brandon and Walker, 2005, and references therein).
Motion and rigidity of the Pacific Plate and implications for plate boundary deformation
Journal of Geophysical Research, 2002
1] Using up to 11 years of data from a global network of Global Positioning System (GPS) stations, including 12 stations well distributed across the Pacific Plate, we derive present-day Euler vectors for the Pacific Plate more precisely than has previously been possible from space geodetic data. After rejecting on statistical grounds the velocity of one station on each of the Pacific and North American plates, we find that the quality of fit of the horizontal velocities of 11 Pacific Plate (PA) stations to the best fitting PA Euler vector is similar to the fit of 11 Australian Plate (AU) velocities to the AU Euler vector and 2020% better than the fit of nine North American Plate (NA) velocities to the NA Euler vector. The velocities of stations on the Pacific and Australian Plates each fit a rigid plate model with an RMS residual of 0.4 mm/yr, while the North American velocities fit a rigid plate model with an RMS velocity of 0.6 mm/yr. Our best fitting PA/AU relative Euler vector is located 20170 km southeast of the NUVEL-1A pole but is not significantly different at the 95% confidence level. It is also close (<70 km in position and <3% in rate) to a pole derived from transform faults identified from satellite altimetry, suggesting that the vector has not changed significantly over the past 3 Myr. Our relative Euler vector is also consistent with all known geological and geodetic evidence concerning the AU/PA plate boundary through New Zealand. The GPS sites offshore of southern California are presently moving 4-5 ± 1 mm/yr relative to predicted Pacific velocity, with their residual velocities in approximately the opposite direction to PA/NA relative motion. Likewise, the easternmost sites in South Island, New Zealand, are moving $3 ± 1 mm/yr relative to predicted Pacific velocity, with the residuals in approximately the opposite direction to PA/AU relative motion. These velocity residuals are in the same sense as predicted by elastic strain accumulation on known plate boundary faults but are of a significantly higher magnitude in both southern California and New Zealand, implying that the plate boundary zones in both regions are wider than previously believed.
Journal of Geophysical Research, 2009
1] Here, I present a new absolute plate motion model of the Earth's surface, determined from the alignment of present-day surface motions with 474 published shear wave (i.e., SKS) splitting orientations. When limited to oceanic islands and cratons, splitting orientations are assumed to reflect anisotropy in the asthenosphere caused by the differential motion between lithosphere and mesosphere. The best fit model predicts a 0.2065°/Ma counterclockwise net rotation of the lithosphere as a whole, which revolves around a pole at 57.6°S and 63.2°E. This net rotation is particularly well constrained by data on cratons and/or in the Indo-Atlantic region. The average data misfit is 19°and 24°for oceanic and cratonic areas, respectively, but the normalized root-mean-square misfits are about equal at 5.4 and 5.2. Predicted plate motions are very consistent with recent hot spot track azimuths (<8°on many plates), except for the slowest moving plates (Antarctica, Africa, and Eurasia). The difference in hot spot propagation vectors and plate velocities describes the motion of hot spots (i.e., their underlying plumes). For most hot spots that move significantly, the motions are considerably smaller than and antiparallel to the absolute plate velocity. Only when the origin depth of the plume is considered can the hot spot motions be explained in terms of mantle flow. The results are largely consistent with independent evidence of subasthenospheric mantle flow and asthenospheric return flow near spreading ridges. The results suggest that, at least where hot spots are, the lithosphere is decoupled from the mesosphere, including in western North America. Citation: Kreemer, C. (2009), Absolute plate motions constrained by shear wave splitting orientations with implications for hot spot motions and mantle flow,
Geophysical Journal International, 1990
We determine best-fitting Euler vectors, closure-fitting Euler vectors, and a new global model (NUVEL-1) describing the geologically current motion between 12 assumed-rigid plates by inverting plate motion data we have compiled, critically analysed, and tested for self-consistency. We treat Arabia, India and Australia, and North America and South America as distinct plates, but combine Nubia and Somalia into a single African plate because motion between them could not be reliably resolved. The 1122 data from 22 plate boundaries inverted to obtain NUVEL-1 consist of 277 spreading rates, 121 transform fault azimuths, and 724 earthquake slip vectors. We determined all rates over a uniform time interval of 3.0m.y., corresponding to the centre of the anomaly 2A sequence, by comparing synthetic magnetic anomalies with observed profiles. The model fits the data well. Unlike prior global plate motion models, which systematically misfit some spreading rates in the Indian Ocean by 8-12mmyr-', the systematic misfits by NUVEL-1 nowhere exceed -3 mm yr-'. The model differs significantly from prior global plate motion models. For the 30 pairs of plates sharing a common boundary, 29 of 30 P071, and 25 of 30 RM2 Euler vectors lie outside the 99 per cent confidence limits of NUVEL-1. Differences are large in the Indian Ocean where NUVEL-1 plate motion data and plate geometry differ from those used in prior studies and in the Pacific Ocean where NUVEL-1 rates are systematically 5-20 mm yr-' slower than those of prior models. The strikes of transform faults mapped with GLORIA and Seabeam along the Mid-Atlantic Ridge greatly improve the accuracy of estimates of the direction of plate motion. These data give Euler vectors differing significantly from those of prior studies, show that motion about the Azores triple junction is consistent with plate circuit closure, and better resolve motion between North America and South America. Motion of the Caribbean plate relative to North or South America is about 7mmyr-' slower than in prior global models. Trench slip vectors tend to be systematically misfit wherever convergence is oblique, and best-fitting poles determined only from trench slip vectors differ significantly from their corresponding closure-fitting Euler vectors. The direction of slip in trench earthquakes tends to be between the direction of plate motion and the normal to the trench strike. Part of this bias may be due to the neglect of lateral heterogeneities of seismic velocities caused by cold subducting slabs, but the larger part is likely caused by independent motion of fore-arc crust and lithosphere relative to the overriding plate.
A high-resolution model for Eurasia-North America plate kinematics since 20 Ma
Geophysical Journal International, 2008
We derive the first chronologically detailed model of Eurasia-North America plate motion since 20 Ma from ship and airplane surveys of the well-expressed magnetic lineations along this slowly spreading plate boundary, including previously unavailable dense Russian magnetic data from the southern Reykjanes Ridge and northern Mid-Atlantic ridge near the Charlie Gibbs fracture zone. From more than 7000 crossings of 21 magnetic anomalies from Anomaly 1n (0.78 Ma) to Anomaly 6n (19.7 Ma), we estimate best-fitting finite rotations and realistic uncertainties. Linear regressions of total opening distances versus their reversal ages at different locations along the plate boundary show that reversal boundaries are shifted systematically outwards from the spreading axis with respect to their idealized locations, with the outward shift ranging from more than 5 km between Iceland and the Charlie Gibbs fracture zone to ∼2 km elsewhere. This outward displacement, which is a consequence of the finite zone of seafloor accretion, degrades estimates of the underlying plate motion and is thus removed for the ensuing kinematic analysis. The corrected plate motion rotations reveal surprising, previously unrecognized features in the relative motions of these two plates. Within the uncertainties, motion was steady from 20 to 8 Ma around a pole that was located ∼600 km north of the present pole, with seafloor spreading rates that changed by no more than 5 per cent (1 mm yr −1 ) along the Reykjanes Ridge during this period. Seafloor spreading rates decreased abruptly by 20 ± 2 per cent at 7.5-6.5 Ma, coinciding with rapid southward migration of the pole of rotation and a 5 • -10 • counter-clockwise change in the plate slip direction. Eurasia-North America plate motion since 6.7 Ma has remained remarkably steady, with an apparently stationary axis of rotation and upper limit of ±2 per cent on any variations in the rate of angular rotation during this period. Based on the good agreement between seismotectonic constraints on present deformation in northeast Asia and directions of motion that are predicted by our 6.7 Ma to present pole, we hypothesize that motion has remained steady to the present and attempt to test this hypothesis with published GPS estimates for Eurasia-North America motion. We find, however, that GPS estimates that are tied to recent versions of the international geodetic reference frame and rely principally on station velocities from Europe give implausible estimates of recent motion, with the most recently published GPS model predicting convergence along the southern Gakkel Ridge and in the Laptev Sea, where seafloor spreading occurs. An alternative GPS estimate that is not tied to the international terrestrial reference frame and employs GPS station velocities from northeastern Asia is marginally consistent with our 6.7-0 Ma motion estimate.
Global plate motion frames: Toward a unified model
Reviews of Geophysics, 2008
1] Plate tectonics constitutes our primary framework for understanding how the Earth works over geological timescales. High-resolution mapping of relative plate motions based on marine geophysical data has followed the discovery of geomagnetic reversals, mid-ocean ridges, transform faults, and seafloor spreading, cementing the plate tectonic paradigm. However, so-called ''absolute plate motions,'' describing how the fragments of the outer shell of the Earth have moved relative to a reference system such as the Earth's mantle, are still poorly understood. Accurate absolute plate motion models are essential surface boundary conditions for mantle convection models as well as for understanding past ocean circulation and climate as continent-ocean distributions change with time. A fundamental problem with deciphering absolute plate motions is that the Earth's rotation axis and the averaged magnetic dipole axis are not necessarily fixed to the mantle reference system. Absolute plate motion models based on volcanic hot spot tracks are largely confined to the last 130 Ma and ideally would require knowledge about the motions within the convecting mantle. In contrast, models based on paleomagnetic data reflect plate motion relative to the magnetic dipole axis for most of Earth's history but cannot provide paleolongitudes because of the axial symmetry of the Earth's magnetic dipole field. We analyze four different reference frames (paleomagnetic, African fixed hot spot, African moving hot spot, and global moving hot spot), discuss their uncertainties, and develop a unifying approach for connecting a hot spot track system and a paleomagnetic absolute plate reference system into a ''hybrid'' model for the time period from the assembly of Pangea ($320 Ma) to the present. For the last 100 Ma we use a moving hot spot reference frame that takes mantle convection into account, and we connect this to a pre -100 Ma global paleomagnetic frame adjusted 5°in longitude to smooth the reference frame transition. Using plate driving force arguments and the mapping of reconstructed large igneous provinces to core-mantle boundary topography, we argue that continental paleolongitudes can be constrained with reasonable confidence. Citation: Torsvik, T. H., R. D. Müller, R. Van der Voo, B. Steinberger, and C. Gaina (2008), Global plate motion frames: Toward a unified model, Rev. Geophys., 46, RG3004,