All elements which are part of the geometry item are deleted. In this way, it is easy to make a mesh with holes, tunneling systems in ground, etc. Remaining nodes in the geometry, are moved onto the edge of the geometry. For these remaining nodes, automatically a node_boundary record will be generated.
If you combine this record with a control_timestep record, then the element will be slowly deleted, starting from a complete element at the start of the timestep up to no element at the end of the timestep. This is accomplished by reducing the nodal forces of the elements slowly to zero; at the end of the timestep, the element is deleted completely. This might be usefull for a better convergence behaviour of the iterative process.