vernal pool

A shallow, seasonal wetland that fills with winter rain on top of an impermeable hardpan layer, holds water through spring, and dries completely by summer — leaving a cracked, bare depression that gives no sign of what it held. In the weeks between filling and drying, vernal pools support an extraordinary community of life found almost nowhere else: fairy shrimp, tiger salamanders, specialized wildflowers that bloom in concentric rings as the water recedes.