code: def _get_min_distance_to_volcanic_front(lons, lats):
      
      vf = _construct_surface(VOLCANIC_FRONT_LONS, VOLCANIC_FRONT_LATS, 0., 10.)
      sites = Mesh(lons, lats, None)
      return vf.get_rx_distance(sites)
docs: Compute and return minimum distance between volcanic front and points
      specified by 'lon' and 'lat'.
  
      Distance is negative if point is located east of the volcanic front,
      positive otherwise.
  
      The method uses the same approach as :meth:`_get_min_distance_to_sub_trench`
      but final distance is returned without taking the absolute value.