Cross contour lines are used to achieve which of the following effects?

Cross contour lines are employed specifically to illustrate the three-dimensional form and surface undulations of an object. This technique involves drawing lines that follow the contours of a surface, effectively capturing the changes in elevation and shape. By using cross contour lines, artists can convey the volume and topography of an object, allowing viewers to perceive its form in a more dynamic way.

The other options focus on different aspects of visual representation. Depth through color involves using shading and color variation to create the illusion of distance, while detailed textures aim to represent the tactile quality of surfaces. Outlining shapes is a foundational drawing technique that establishes form but does not convey the subtleties of surface variation. Hence, cross contour lines are primarily concerned with defining and emphasizing surface undulations, making that the correct choice.