Modeling the Chicxulub impact event (65 Ma)

Hydrocode modeling of Chicxulub as an oblique impact event
E. Pierazzo, H.J. Melosh

Earth Planet. Sci. Lett. 165, 163-176, 1999

ABSTRACT

Since the confirmation the the buried Chicxulub structure is the long-sought K/T boundary crater, numerous efforts have been devoted to modeling the impact event and estimating the amount of target material that underwent melting and vaporization. Previous hydrocode simulations modeled Chicxulub event as a vertical impact. We carried out a series of three-dimensional (3D) hydrocode simulations of the Chicxulub impact event to study how the impact angle affects the results of impact events. The simulations model an asteroid, 10 km in diameter, impacting at 20 km/s on a target resembling the lithology of the Chicxulub site. The angle of impact modeled are 90° (vertical), 60°, 45°, 30°, and 15°. We find that the amount of sediments (surface layer) vaporized in the impact reaches a maximum for an impact angle of 30° from the surface, corresponding to less than two times the amount of vaporization for the vertical case. The degassing of the sedimentary layer, however, drops abruptly for a 15° impact angle. The amount of continental crust melted in the impact decreases monotonically (a consequence of the decrease in the maximum depth of melting) from the vertical impact case to the 15° impact. Melting and vaporization occur primarily in the downrange direction for oblique impacts, due to asymmetries in the strength of the shock wave with respect to the point of impact. The results can be used to scale the information from the available vertical simulations to correct for the angle of impact. A comparison of a 3D vertical impact simulation with a similar two-dimensional (2D) simulation shows good agreement between vertical 3D and 2D simulations.

COLOR FIGURES

Material distribution, with density contours, and temperature shading for a 3D simulations of a Chicxulub-size impactor, 5 seconds after impact.
Density contours are: 10^-6, 10^-5, 10^-4, 10^-3, 10^-2, 10^-1, and 1 g/cm³. Mat 1= Dunite; Mat 2= water; Mat 3= calcite; Mat 4= air; Mat 5= granite.
In the temperature shading plot (part of the GIF image) the temperature ranges between 200 K and 10000 K.

To see and download full figure (density and temperature shading) click on the figures

Impact angle = 90°

Impact angle = 45°

Impact angle = 30°