Google Earth: Galapagos "hotspot" dates: present & restored

New Google Earth data set: Galapagos "hotspot" dates: present & restored.

Ar/Ar and K/Ar dates from Galapagos "hotspot" region.

Two renderings: (1) Present day sample locations and (2) restored locations. (Vertical dimension: Age (Ma) multiplied by 5000 m.)

Restored locations: Rotated back to Hawaiian hotspot reference frame for inferred crystallization age. Hawaiian-Pacific model: Raymond et al. (2000, corrected). Relative plate reconstructions: Pilger (2007 compilation). Interpolated using splined pseudovectors (method of Pilger, 2003). For dates older than 9 Ma from Malpelo Ridge and offshore Panama east of 82 degrees W longitude, it was assumed that they formed on the Cocos plate and were transferred from the Cocos to the Nazca plate at 9 Ma.

Note that oldest dates from Cocos, Carnegie, and Malpelo Ridges cluster in a circle with diameter on the order of 500-600 km.

Sources: White et al (1993), O'Connor et al (2007).

Google Earth: Isotopic Dates from Global "Hotspot" Traces -- Galapagos

I've added an additional data set for the Galapagos "hotspot" to an existing post:

Isotopic Dates from Global "Hotspot" Traces. Scroll to #1070646 - 12/11/07 11:34 AM.

The new data are from: O'Connor J. M., Stoffers, P., Wijbrans, J. R., and Worthington, T. J., 2007, Migration of widespread long-lived volcanism across the Galápagos Volcanic Province: Evidence for a broad hotspot melting anomaly? Earth and Planetary Science Letters, 263, 339-354, doi:10.1016/j.epsl.2007.09.007.In this kmz there is also a folder with K/AR dates from: W.M. White, A.R. McBirney and R.A. Duncan, 1993, Petrology and geochemistry of the Galápagos Islands: portrait of a pathological mantle plume, Journal of Geophysical Research, 98 , 19,533–19,563.

Google Earth: Reconstructed basalts, Western US to Tristan

KAr dates of basalts 40 Ma and younger, western US, from USGS data set. Restored to position relative to Tristan hotspot frame, according to reconstruction model of McQuarrie and Wernicke (2005) and Atwater, plate-hotspot model of Mueller et al. (1993), and plate reconstruction compilation of Pilger (2007).

Google Earth Community kmz data set.

Reconstruction methods.

Current data set locations.

Google Earth: Reconstructed basalts, Western US, to Hawaii

KAr dates of basalts 40 Ma and younger, western US, from USGS data set. Restored to position relative to Hawaiian hotspot frame, according to reconstruction model of McQuarrie and Wernicke (2005) and Atwater, plate-hotspot model of Raymond et al., (2000), recalculated to an age of 47 Ma for the Hawaiian-Emperor bend, and plate reconstruction compilation of Pilger (2007).
Google Earth Community kmz data set

Reconstruction methods

Current data set locations

Google Earth: Restored-basalts-Western US, 0-40Ma

KAr dates of basalts 40 Ma and younger, western US, from USGS data set. Restored to position relative to stable North America according to model of McQuarrie and Wernicke (2005) and Atwater.

Google Earth Community kmz data set

Reconstruction methods

Current locations

Google Earth: Restoration Parameters and Restoring Data Points

McQuarrie and Wernicke (2005) produced a series of reconstructions of the southwestern United States from 36 Ma to present, as discrete blocks displaced from one another and from the stable midcontinent. These reconstructions were defined by shapefiles incorporating polygons outlining each block. Using GeoGraphix Discovery, the polygons in the shapefiles were converted to latitude and longitude. For each block and reconstruction, finite rotations from the reconstructed age to present were calculated. For the northwestern United States, discrete reconstruction sets for two different ages are derived from maps produced by Atwater.
Method for calculating restorations
For a particular reconstruction age, the finite rotation of each block from that age to the present was derived using a four point method. Given points a1 and a2 on Block A, and corresponding points a1' and a2' on rotated Block A': determine that one of the two poles that is 90 degrees away from both points and then the angle that rotates a1' to a1 around the pole. Rotate a2' using the same pole and angle to produce a2''. Then determine the angle (positive or negative) that rotates a2'' to a2 around a1 (serving as the pole). From the two resulting sets of rotation parameters, compute the total, equivalent rotation.

Then, to allow restoration of discrete data points within the reconstruction region, form a grid comparable to or at a higher resolution than the reconstructed block spacing. Convert the reconstruction parameters to pseudovectors with magnitude equal to the rotation angle and assign them to each node of the corresponding block in present-day coordinates. Interpolate the pseudovectors onto the grid using a Gaussian distance filter and the twelve nearest block nodes to the grid node. Because the filter is exponential with distance, grid points falling within a block should produce interpolated pseudovectors equivalent to that assigned to the entire block. The result is three grids for each age corresponding with each pseudovector component and reconstruction age.

Given a discrete data point of a specific age, interpolate the pseudovectors for the two reconstruction ages that bracket the data point age using the same Gaussian distance filter method used to calculate the grid. Then linearly interpolate the pseudovector components using the ages. Convert the pseudovector to rotation parameters and apply to the data point.

Subsequent posts will provide examples of this approach.

Basalts of the Western US in Google Earth

Isotopic age dates in Ma (millions of years before present) of basaltic igneous rocks from western United States, 0-40 Ma. Source: US Geological Survey. Posted on Google Earth Community website: Link.

This is a reduction of the larger data set posted previously (US Cordilleran Igneous Isotopic Dates LT 40 Ma).

SW US Reconstructions in Google Earth

McQuarrie and Wernicke (2005) produced a highly detailed series of reconstructions of the principal tectonic blocks of the southwestern United States from 36 Ma to Present. I have converted the shapefiles they produced to single KMZ file for viewing in Google Earth, including a set of polygons for each reconstruction age.

From their reconstructions, I have derived equivalent finite rotation parameters for each tectonic block from the reconstruction age to present. Watch for subsequent posts that utilize these parameters...

Source: McQuarrie, N., and Wernicke, B.P., An animated tectonic reconstruction of Southwestern North America since 36 Ma, Geosphere; December 2005; v. 1; no. 3; p. 147-172; DOI: 10.1130/GES00016.1. http://geosphere.geoscienceworld.org/cgi/content/abstract/1/3/147

Plate-Hotspot Loci in Google Earth

A new model data set is available for Google Earth: Pacific and Nazca plate loci in four frames .

These calculated loci, representing motion of the Pacific and Nazca plates in four different reference frames, demonstrate the remarkable correspondence of motion among the Hawaiian hotspot frame and the North and South American plates. Pilger (2007) has discussed the implications of this correspondence for the existence of at least two different hotspot reference frames: Hawaiian (beneath the plates of the Pacific) and Tristan (beneath the Atlantic and Indian Oceans and adjacent continents). This contrasts with the persistent assumption that the global hotspot set represents a single hotspot reference frame. By viewing in Google Earth, the correspondence is apparent over the extent of the Pacific plate where long-lived hotspot traces exist.

Data sharing via Google Earth

I've prepared an introduction to Google Earth, together with a proposal for other Earth Scientists to add tectonically-oriented data sets to the Google Earth Community website. This proposal is posted at: http://www.mantleplumes.org/WebDocuments/GoogleEarthProposal.pdf.

Google Earth Post: Isotopic Dates: Andean Igneous Rocks LE 150 Ma

Here is a compilation in progress:

Isotopic Dates: Andean Igneous Rocks LE 150 Ma

More data are welcome.

Google Earth data sets: Plates and Hotspots Update

All of the Google Earth datasets previously posted have been moved to a different Google Earth Category.

Here are the new links:

Isotopic Dates from East African Volcanics
US Cordilleran Igneous Isotopic Dates LT 40 Ma
Isotopic Dates from Global "Hotspot" Traces
Average Ages for Pacific Hotspot Sample Locations
Stresses - Present to 130 Ma
Hotspot rotback
Isotopic Dates from Baksi (1999) - Original Data
Recalculated Isotopic Dates from Baksi (1999)
Isotopic Dates Compiled by O'Neill et al (2005)
Magnetic Isochrons from Müller et al (1997)
Ar/Ar Dates from Hawaiian-Emperor Chain
Don Anderson's Hotspot Compilation
SWOOSH: Plate-Hotspot Motions, Tristan-No. America
SWOOSH: Plate-Hotspot Motions, Hawaii-No. America
SWOOSH: Plate-Hotspot Motions, Tristan-No. Africa
SWOOSH: Plate-Hotspot Motions, Tristan-Cen. Africa
SWOOSH: Plate-Hotspot Motions, Tristan-So. America
SWOOSH: Plate-Hotspot Motions, Tristan-Australia
Pacific "Hotspot" Isotopic Ages by Koppers et al

(Links in previous posts have been updated.)

Pacific "Hotspot" ages from Koppers et al.

Published isotopic age dates from three publications have been posted on the Google Earth Community site, Pacific "Hotspot" Isotopic Ages by Koppers et al

Koppers, A. A. P., Staudigel, H., Pringle, M. S., Wijbrans, J. R., 2003, Short-lived and discontinuous intraplate volcanism in South Pacific: Hot spots or extensional volcanism? Geochemistry, Geophysics, Geosystems, 4, doi:10.1029/2003GC000533.
Koppers, A. A. P., Duncan, R. A., Steinberger, B., 2004, Implications of a nonlinear 40Ar/39Ar age progression along the Louisville seamount trail for models of fixed and moving hot spots, Geochemistry, Geophysics, Geosystems, 5, doi:10.1029/2003GC000671.
Koppers, A. A. P., and Staudigel, H., 2005, Asynchronous Bends in Pacific Seamount Trails: A Case for Extensional Volcanism? Science, 307, 904-907.

SWOOSH - New Data Sets

A series of new data sets have been posted to the Google Earth Community - instantaneous motion directions in hotspot reference frames for comparison with stress orientations.

SWOOSH: Plate-Hotspot Motions, Tristan-No. America
SWOOSH: Plate-Hotspot Motions, Hawaii-No. America
SWOOSH: Plate-Hotspot Motions, Tristan-No. Africa
SWOOSH: Plate-Hotspot Motions, Tristan-Cen. Africa
SWOOSH: Plate-Hotspot Motions, Tristan-So. America
SWOOSH: Plate-Hotspot Motions, Tristan-Australia

Don Anderson's Hotspot Compilation in Google Earth

Don Anderson has posted two spreadsheets of contemporary hotspot locations and properties based on a large number of references on the Mantle Plumes website: The Compleate Hot Spot, web page , accessed September 4, 2007. I have merged and converted the spreadsheets into a Google Earth kmz file: Don Anderson's Hotspot Compilation. Don's tabulated information is concatenated into the description field of the data set. In a couple of cases (Galapagos and Marquesas) I've noted that the posted locations appear to be displaced from what other workers have postulated.

Google Earth data sets: Plates and Hotspots

Google Earth is an exciting new visualization platform for geological and geophysical data (as well as other types). It is especially useful for seeing information pertinent to plate tectonics: isotopic ages of “hotspot” and subduction-related magmatism, contemporary and paleo-stress indicators, magnetic isochrons, plate reconstructions, and plate-hotspot models.

I have posted a number of such data sets on the Google Earth Community website. The links below provide access to Google Earth native format (“kmz”) data sets. More information is provided with each post and internally in each data set.

Isotopic Dates from East African Volcanics
US Cordilleran Igneous Isotopic Dates LT 40 Ma
Isotopic Dates from Global "Hotspot" Traces
Average Ages for Pacific Hotspot Sample Locations
Stresses - Present to 130 Ma
Hotspot rotback
Isotopic Dates from Baksi (1999) - Original Data
Recalculated Isotopic Dates from Baksi (1999)
Isotopic Dates Compiled by O'Neill et al (2005)
Magnetic Isochrons from Müller et al (1997)
Ar/Ar Dates from Hawaiian-Emperor Chain

I intend to post more data sets to the Google Earth Community site, with links noted here, too.

Geokinematics: Prelude to Geodynamics

Geokinematics: Prelude to Geodynamics ... can be obtained from Amazon. It's also in almost every major U.S. university library.

Improved Plate-Hotspot Modeling

(2/27/05) The recent contribution of Wessel, Harada, and Kroenke at the Fall, 2004, AGU (link) is a natural next step in modeling Pacific plate motions relative to hotspots. By taking the seamount catalog, applying Harada and Hamano's modeling techniques, and leaving hotspot location as an unknown to be solved for, the results WHK have come up with are very promising.
The big limitation, of course, is coming up with precise and accurate isotopic dates to more fully test and time-parameterize the model. My suggestion is: incorporate the Tuamotu and Nazca ridges. I showed (with David Handschumacher) in 1981 that the two ridges probably originated from the same sublithospheric melting anomaly centered on the Pacific-Nazca (Farallon) ridge between magnetic chrons 11 and 21. Thus, when reconstructed, the intersection of the restored ridges provides ages of the ridges. So, assuming a correct geomagnetic time scale, at least part of the kinematic model could be constrained.

Update: (3/2/05) One could also incorporate the islands and seamounts of the Easter to Sala-y-Gomez chain (assuming that they formed from an Easter hotspot largely located beneath the Nazca plate). However, given the need to rotate them to the Pacific plate and their age uncertainty (which would make their rotated locations less certain), and the lack of tightly spaced (in time) Pacific-Nazca reconstructions since 25 Ma, this seems less promising.

Original Post Link: http://mesoplates.spaces.live.com/blog/cns!F9234EE50D713CDC!139.entry

New evidence for sublithospheric hotspots

Koppers and Staudigel's (2005) recent contribution to knowledge of the age of Pacific Seamount chains produces a conclusion that can be inverted. The title concisely states their inference: "Asynchronous bends in Pacific seamount trails: a case for extensional volcanism?"
Taking previous speculations that the Gilbert Ridge and Tokelau Seamounts include a "bend" analogous to the Hawaiian-Emperor bend, K&S show that isotopic ages from the two chains are incompatible with the age of the H-E bend and with one another. Within their published figures, they show hypothetical loci generated by a Pacific hotspot model and demonstrate inconsistency with their newly acquired dates. Interestingly, for the Toekalu chain, they also show a locus anchored at Macdonald "hotspot" -- which better fits the new ages of the seamounts.
Comparison of K&S's inferred seamount chains and their included bends with Smith and Wessel's (1999) bathymetry suggests a certain selectivity in interpretation, especially given the short length of the "younger" portions inferred to mimic the younger part of the H-E chain. Putting such subjective observations aside, there is another way to look at the significance of the new data in light of a relatively fixed sub-Pacific hotspot reference frame.
Taking the new data points, along with previously published data, I've reconstructed each sample date back to its location when the isotopic clock started according to the plate-hotspot model of Raymond et al. (2000) as interpolated using my spline methods (Pilger, 2003). Given the age uncertainty, I've included data points +/- 5 m.y. around each data point at 2.5 m.y. intervals (producing a maximum of five data points), thereby defining loci segments.
The restored loci from the Gilbert and Tokelau chains (click thumbnail below) produce a fascinating pattern when combined with the restored segments from the Cook-Austral chain. The two older chains produce loci that intersect with younger segments close to (1) the inferred location of the Macdonald hotspot and (2) another inferred hotspot location.
Previously, available isotopic dates from the C-A chain implied a miinimum of two hotspots (three if the older part of the Foundation chain were included). K&S's new data strengthen this inference.
Additionally, then, the approximate alignment of the three hotspots cannot as readily be ascribed to intraplate stresses as might previously have been inferred. Why? Because the Gilbert and Tokelau chains are not themselves aligned. That is, the melting anomalies responsible for the two older chains are not attributable to a single locus of intraplate extension. The alignment of the "hotspots" post-47 Ma is largely a coincidence.
Thus, the new data of K&S don't strengthen the case for intraplate extension, they undermine it.
Perhaps the revised title could be: "New isotopic ages from Pacific seamount chains: Further evidence for sub-lithospheric hotspots?"
Cited: Koppers and Staudigel (2005) Science, 307, 904. Pilger (2003) Geokinematics: Prelude to Geodynamics. Raymond et al. (2000) AGU Geophys. Mon.121, 359. Smith and Sandwell (1997) Global seafloor topography from satellite altimetry and ship depth soundings, Science, 277, 1957.

Originally posted at: http://mesoplates.spaces.live.com/blog/cns!F9234EE50D713CDC!149.entry

Mesoplates...

Wikipedia entry: http://en.wikipedia.org/wiki/Mesoplates.

GSA Article...The Bend

See a discussion of the kinematic significance of the Hawaiian-Emperor Bend at:

Pilger, R. H., 2007, The Bend: Origin and significance, Bull. Geol. Soc. Am., 119, 302-313.

Mesoplates

Here's a link to another web log which deals with plate reference frames: http://mesoplates.spaces.live.com/default.aspx.