add mesa example

examples/block_hill_with_mesa.txt

@@ -0,0 +1,28 @@
+# GrainHill input file:
+#
+# block_hill_with_mesa: "block hill" model that includes a cell state to
+# represent boulders. Here boulders form a horizontal layer that creates
+# a mesa. Similar to Figure 18a in Tucker et al. (2018).
+#
+model_type: 'blockhill'
+number_of_node_rows: 43
+number_of_node_columns: 101
+cell_width: 0.1
+grav_accel: 9.8
+friction_coef: 1.0
+run_duration: 3000.0
+uplift_interval: 100.0
+uplift_duration: 3000.0
+disturbance_rate: 0.01
+weathering_rate: 0.0005
+rock_state_for_uplift: 7
+block_layer_dip_angle: 0.0
+block_layer_thickness: 10.0
+y0_top: 0.0
+opt_rock_collapse: 1
+save_plots: True
+plot_filename: 'block_hill_with_mesa'
+plot_filetype: '.png'
+plot_interval: 600.0
+output_interval: 1.0e20
+report_interval: 5.0