Cracking on the surface is normal and a desired result when baking quick breads such as this Pumpkin Pecan Bread. However, excessive cracking and long tunnels can be caused by overmixing. To avoid excessive cracking, mix until the dry ingredients are JUST combined with the wet ingredients. There may be some lumps in the batter, but that is completely fine. But rest assured, the cracks in the bread will not alter the flavor and it will still taste delicious!