Dry Valley

Valleys without a surface stream are very common in karst areas. They were formed in two ways:

  1. In times before the water table was too deep, the water drained on the surface.
  2. During the Ice Ages, the ground was frozen for several meters below the surface. Summer was too short to melt it this deep. But the frozen ground is water resistant, all cracks are filled with ice. So the drainage happened on the surface.