 Total average precipitation in the Craters of the Moon area is between 15 – 20 inches ( 380 – 510 mm ) per year . Most of this is lost in cracks in the basalt , only to emerge later in springs and seeps in the walls of the Snake River Canyon . Older lava fields on the plain have been invaded by drought @-@ resistant plants such as sagebrush , while younger fields , such as Craters of the Moon , only have a seasonal and very sparse cover of vegetation . From a distance this cover disappears almost entirely , giving an impression of utter black desolation . Repeated lava flows over the last 15 @,@ 000 years have raised the land surface enough to expose it to the prevailing southwesterly winds , which help to keep the area dry . Together these conditions make life on the lava field difficult . 
