# Circular landforms¶

Left figure shows a satellite image draped over a topographic model of Kondyor Massif, Russia. [Credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team]

The above circular landform is neither a crater nor a volcano, have a look at this post for an explanation of its formation.

In this example, we analyse a central pit crater geomorphological evolution over 200k years induced by an uniform precipitation (1 m/a).

Central pit craters are a crater type that contains an approximately circular depression in their central peak. These craters have been found on Earth, Mars or Ganymede. Here we use their typical shape to perform a high resolution simulation using Badlands.

The initial grid has an approximate resolution of 10 m and consists of a 2.5 by 2.5 km circular crater of 570 m high with a central pit of 380 m depth.

## Initial settings¶

For this model, we use the stream power law sediment transport model which scale the incision rate $E$ as a power function of surface water discharge $A$ and slope $S=\nabla z$:

$$E = \kappa A^m (\nabla z)^n$$

where $\kappa$ is the erodibility coefficient dependent on lithology and mean precipitation rate, channel width, flood frequency, channel hydraulics.

The values given to these parameters ($\kappa$, $m$, $n$) need to be set in the XmL input file.

### Depression filling method¶

To handle depression in this version of Badlands (v 2.0.) we use a modified version of Planchon & Darboux depression-filling algorithm. In this approach the time step is automatically adjust in order to ensure stability and to prevent formation of depositional mount. The method consists in filling depressions with lakes of user-imposed maximum depth (parameter fillmax) and simulating the filling of the lake as an iterative process.

First we initialise the model and set the path to the XmL input file.

You can edit the XmL configuration file at /edit/volume/Examples/crater/crater.xml.

To view the complete XmL options you can follow this link to github page: complete.xml.

In [1]:
from pyBadlands.model import Model as badlandsModel

# initialise model