Chicxulub crater formation
The model is an attempt to reproduce the Chicxulub crater. It is a low-resolution model of an impact of a 14.4 km diameter asteroid striking a layered target at 12 km/s. The impactor is a sphere of material represented using an ANEOS-derived equation of state table for granite. The target has a surface gravity of 9.81 m/s^2 and comprises 2.8 km sediments (calcite) above 30 km crust (granite), above mantle (dunite). Each material's equation of state is defined using ANEOS-derived tables. Acoustic fluidization (AF) is used to weaken the target and facilitate complex crater collapse.
The model is similar to those described by Ivanov (2005), Collins et al. (2008) and Christeson et al. (2009), which provided a reasonable fit to observational constraints. This test case model differs because (a) different AF parameters to those used in other models are assigned to the mantle, crust and sediments; and (b) no geotherm is set in this example - the target has a constant temperature of 293K.
Go to the relevant example directory
cd /share/examples/Chicxulub
Run iSALE2D. The simulation will take several hours, so this should be run in the background.
./iSALE2D &
To produce images of the simulation to visualise the temperature and material movement using pySALEPlot:
python Plotting/MatTmp.py
The images, which should be identical to those shown below, will be output to the directory MatTmp/. The pySALEPlot plotting scripts (see also <prefix>/share/examples/Chicxulub/Plotting/YldYAc.py) can easily be modified to generate additional images and analysis.
In addition, this psp_plot_vertical_profiles plots a vertical profile of pressure at two time steps from the Chicxulub simulation.
Model parameters for simulation.
| DESCRIPTION | VALUE |
|---|---|
| Number of high-resolution cells in x-direction | 250 |
| Number of high-resolution cells in y-direction | 200 |
| Cell size in x-direction (m) | 400 |
| Cell size in y-direction (m) | 400 |
| Surface temperature (deg. Kelvin) | 293 |
| Gravitational acceleration (m/s2) | 9.81 |
| Projectile diameter (km) | 14.4 |
| Projectile velocity (km/s) | 12. |
| Projectile material (number) | granite |
Target layers for simulation.
| MATERIAL LAYER | THICKNESS (m) |
|---|---|
| calcite | 2800.0 |
| granite | 30000.0 |
| dunite_ | 17200.0 |
Material model parameters.
| DESCRIPTION | granite | dunite_ | calcite |
|---|---|---|---|
| Poisson ratio | 0.30 | 0.25 | 0.30 |
| Strength at zero pressure (intact; MPa) | 10. | 10. | 5. |
| Strength at inf. pressure (intact; MPa) | 2500. | 3500. | 500. |
| Internal friction coeff. (intact) | 2.00 | 1.20 | 1. |
| Strength at zero pressure (damaged; MPa) | 0.01 | 0.01 | 0.01 |
| Friction coefficient (damaged) | 0.60 | 0.60 | 0.40 |
| Melt Temperature (degrees Kelvin) | 1673. | 1373. | 1500. |
| Specific Heat Capacity (J/Kg/Kelvin) | 1000. | 1000. | 1000. |
| Thermal Softening parameter | 1.20 | 1.20 | 1.20 |
| Simon parameters for Melt Temp. vs P. | 6000. | 1520. | 6000. |
| Simon parameters for Melt Temp. vs P. | 3.00 | 4.05 | 3.00 |
| Visc. of ac. fluid. target (m2/s) | 288000. | 2880000. | 0. |
| Decay time for block oscillations (s) | 165.60 | 72.00 | 0. |
| A.F. viscosity scaling paramameter | 0.0080 | 0.080 | 0. |
| A.F. decay time scaling parameter | 120. | 500. | 0. |
Simulation setup is written in asteroid.inp:
------------------- General Model Info ---------------------------------
VERSION __DO NOT MODIFY__ : 4.1
DIMENSION dimension of input file : 2
PATH Data file path : ./
MODEL Modelname : Chicxulub
------------------- Mesh Geometry Parameters ---------------------------
GRIDH horizontal cells : 0 : 250 : 60
GRIDV vertical cells : 60 : 200 : 20
GRIDEXT ext. factor : 1.05d0
GRIDSPC grid spacing : 4.D2
CYL Cylind. geometry : 1.0D0
GRIDSPCM max. grid spacing : -20.D0
------------------- Global setup parameters -----------------------------
S_TYPE setup type : DEFAULT
T_SURF Surface temp : 293.D0
GRAV_V gravity : -9.81D0
------------------- Projectile ("Object") Parameters --------------------
OBJNUM number of objects : 1
OBJRESH CPPR horizontal : 18
OBJVEL object velocity : -1.2D4
OBJMAT object material : granite
OBJDAM object damage : 1.D0
OBJTYPE object type : SPHEROID
------------------- Target Parameters ----------------------------------
LAYNUM layers number : 3
LAYPOS layer position : 103 : 178 : 185
LAYMAT layer material : dunite_ : granite : calcite
LAYTPROF thermal profile : CONST : CONST : CONST
------------------- Time Parameters ------------------------------------
DT initial time increment : 5.0D-3
DTMAX maximum timestep : 5.D-2
TEND end time : 6.001D2
DTSAVE save interval : 5.D0
------------------- Ac. Fluid. Parameters (see also material.inp) ------
TOFF toff : 16.D0
CVIB c_vib : 0.1D0
VIB_MAX Max. vib.vel. : 200.
------------------- Boundary Condition Parameters ----------------------
BND_L left : FREESLIP
BND_R right : FREESLIP
BND_B bottom : NOSLIP
BND_T top : OUTFLOW
------------------- Numerical Stability Parameters ---------------------
AVIS art. visc. linear : 0.24D0
AVIS2 art. visc. quad. : 1.20D0
------------------- Tracer Particle Parameters -------------------------
TR_QUAL integration qual. : 1
TR_VAR add. tracer fiels : #TrP-TrT#
------------------- Control parameters (global) ------------------------
STRESS Consider stress : 1
------------------- Data Saving Parameters -----------------------------
QUALITY Compression rate : -50
VARLIST List of variables : #Den-Tmp-Pre-Sie-Yld-YAc-Dam-VEL#
------------------------------------------------------------------------
Material parameters used in the model are written in material.inp:
----------------------------------------------------------------------------- MATNAME Material name : granite : dunite_ : calcite EOSNAME EOS name : granit2 : dunite_ : calcite EOSTYPE EOS type : aneos : aneos : aneos STRMOD Strength model : ROCK : ROCK : ROCK DAMMOD Damage model : IVANOV : IVANOV : IVANOV ACFL Acoustic fluidisation : BLOCK : BLOCK : BLOCK PORMOD Porosity model : NONE : NONE : NONE THSOFT Thermal softening : OHNAKA : OHNAKA : OHNAKA LDWEAK Low density weakening : POLY : POLY : POLY ---------------------------------------------------------------------------- POIS pois : 3.0000D-01 : 2.5000D-01 : 3.0000D-01 ---------------------------------------------------------------------------- TMELT0 tmelt0 : 1.6730D+03 : 1.3730D+03 : 1.5000D+03 CHEAT C_heat : 1.0000D+03 : 1.0000D+03 : 1.0000D+03 TFRAC tfrac : 1.2000D+00 : 1.2000D+00 : 1.2000D+00 ASIMON a_simon : 6.0000D+09 : 1.5200D+09 : 6.0000D+09 CSIMON c_simon : 3.0000D+00 : 4.0500D+00 : 3.0000D+00 ---------------------------------------------------------------------------- YDAM0 ydam0 (ycoh) : 1.0000D+04 : 1.0000D+04 : 1.0000D+04 FRICDAM fricdam : 6.0000D-01 : 6.0000D-01 : 4.0000D-01 YLIMDAM ylimdam : 2.5000D+09 : 3.5000D+09 : 5.0000D+08 ---------------------------------------------------------------------------- YINT0 yint0 : 1.0000D+07 : 1.0000D+07 : 5.0000D+06 FRICINT fricint : 2.0000D+00 : 1.2000D+00 : 1.0000D+00 YLIMINT ylimint : 2.5000D+09 : 3.5000D+09 : 5.0000D+08 ---------------------------------------------------------------------------- IVANOV_A Damage parameter : 1.0000D-04 : 1.0000D-04 : 1.0000D-04 IVANOV_B Damage parameter : 1.0000D-11 : 1.0000D-11 : 1.0000D-11 IVANOV_C Damage parameter : 3.0000D+08 : 3.0000D+08 : 3.0000D+08 ---------------------------------------------------------------------------- GAMETA gam_eta : 8.0000D-03 : 8.0000D-02 : 0.0000D-03 GAMBETA gam_beta : 1.1500D+02 : 0.5000D+02 : 0.0000D+02 ----------------------------------------------------------------------------
The figures below show a time series of the formation of the Chicxulub crater: (a) at the initial state (b) after 20 s (c) after 80 s (d) after 120 s (e) after 200 s (f) after 600s of the initial impact state. The right panel displays the material type (sediment/crust/mantle); the left side displays the temperature (maximum temperature is 1500K).
