Far-Field Bolide-Impact Strains on Earth  Rev. 0210

Crustal strains and plate motions with respect to 2 known and 6 suspected impact events
Crustal fractures, welts, wedges and ovelapping strain fields from oblique impacts
The End Cretaceous Chicxulub event
The Late Eocene Chespapeake Invader; wedge drift from post-impact plate rotation
Suspected Paleozoic Shaanxi impact, central China

Suspected End Permian impact in the Congo Basin, Africa
Suspected Early Cretacous Mid-Pacific Mts impact complex; precursor of the Cretaceous long normal event?
Suspected Miocene-age impacts in the South Georgia rise and the Argentine abyssal plain, southwest Atlantic Ocean

Suspected Eocene-age impact in the Norfolk basin, West Pacific
Suspected Tertiary age impacts in the Canada basin, Arctic Ocean


Far-field crustal strains on Earth are mapped below with respect to known and suspected bolide-impact carters. Maps for each impact site are generated using geographic information systems  (GIS) and computer-aided drafting (CAD) software with spatial coordinates registered in both geographic and spherical space. The spherical system uses a Lambert equal-area projection  centered on the impact for a single impact, or about the approximate center of an impact complex for more complex ,multiple -impact events. The physical relationships of the known impacts have helped constrain aspects of the suspected ones. These impact events on Earth are thought to influence, and perhaps help drive plate tectonic motions. This work is in progress, and is an evolving record of my observations and thoughts on the structural and geodynamic processes stemming from large, hypervelocity, bolide impacts on terrestrial planets. As such, it represents a departure from current plate tectonic theory for Earth, that relies on other causal mechanisms for driving tectonic plate motions. I'm assembling these ideas using the world-wide-web in an effort to communicate the hypothesis and to advance our understanding of Earth's geodynamic processes, many of which remain sketchy. The basic hypothesis is that far-field crustal strains stemming from large impact events are a substantial component of a more comprehensive plate-tectonic theory that includes large-scale tectonic strains, and long lasting geodynamic processes stemming from very-high-energy bolide impacts on terrestrial planets.  I hope you will recognize these strain effects as more that just cooincidental trends, and entertain the idea that large bolide impacts spur deep-seated processes that are not yet fully understood aspects of plate-tectonic theory.

Crustal strains and plate motions with respect to 2 known and 6 suspected impact events

Far-field strains on Earth from 2 known (Chicxulub and Chesapeake) and 6 suspected impact sites (Canada basin, Congo basin, Mid-Pacific Mountains, Norfolk basin, Shaanxi, South Georgia) are shown below. Splash rings are shown using colored line traces at 660, 1550 and 2900 km radius around each impact. The rings trace circumferential regions of uplift and subsidence around each site. Black vectors show current, horizontal azimuth and magnitude of tectonic-plate motions based on NASA JPL GPS data. Vector lengths are variably-scaled with the horizontal velocity for each GPS station multiplied by 0.25 geographic degrees. The average horizontal velocity for the crustal plates is about 27 mm/yr based on time-series data for 778 GPS stations. Station points are color coded blue for stations having negative vertical motion (subsidence) and green for positive (uplift), respectively. Red-dashed lines originate at impact craters and extend foreland of each crater in the direction of crustal compression; in line with interpreted paths of oblique descent for the different projectiles.  The thin-dashed, colored lines trace surface features including ocean-floor transform faults and other continental lineaments that highlight crustal fractures and faults that either stem from far-field strains associated with the different impact events, or are perturbed by them. Tectonic-plate boundaries are shown as thick maroon and black lines. The thin gray lines on the sea floor trace the M34 magnetic isochron.

Click on the image for more resolution. Click here for a Google Earth KMZ  file of this map..
2 Known and 6 Suspected Impacts, Plate Boundaries and Motions

Plate motions in the southern hemisphere currently diverge northward away from the suspected impacts near South Georgia in the southwest Atlantic Ocean. Plate motions also move in line and away from suspected impacts in the Norfolk basin in the southwest Pacific Ocean and the Canada basin in the Arctic Ocean. However, plate motions associated with the Chicxulub impact and a suspected (Middle Paleozoic?) impact in the Shaanxi province of China are pivoting around these impact sites, suggesting that large impacts can temporarily pin the crust to the mantle. Taken together, these relationships show that large impact events produce long-lasting geodynamic responses,  probably operating to dissipate energy fluxes imparted by large-impact events.  Moreover, most of these impacts show nearby fragmentation of tectonic plates, especially in hinterland regimes of crustal extension. Large-bolide impacts therefore appear to drastically influence Earth geodynamics to a degree that we are only beginning to realize.

The South Georgia event may have occurred in the Middle Miocene during the Langhian (13.65–15.97 mya) stage when there was a sudden warming trend in Antarctica (~15.7 mya ), changes in  Atlantic and Pacific ocean circulation, and subsequent extinction waves of  terrestrial and aquatic life forms (~14.8 to 14.5 mya). The distribution of tektites in the North American tektite strewn field also shows a remarkable spatial coincidence with the proposed foreland trajectory of the South Georgia impacts even though it is currently thought to stem from the Chesapeake impact of Eocene age (~35 Ma).

To be continued.....