Some may be Northern Volcanic Mudflow Vernal Pools. Northern Basalt Flow Vernal Pools are the most common type. They range from fractions of an acre to over 100 acres in size. On the Devil's Garden they occur singly or in clusters of several large pools on flat plains surrounded by sagebrush scrub and juniper woodland. These include such prominent ones as Poison Lake and Egg Lake.
Some pools are underlain by very shallow soil over bedrock.
Current acreage for types is unavailable. The majority of the region is not heavily impacted, being one of the most sparsely populated areas of the state. However, conversion of valley area pools near Burney, Fall River Mills, and Alturas to agriculture has had some overall negative impact. Long-term intensive livestock grazing is the principal unnatural impact over much of the region. Although most indications are that its effects are slight to moderate, effects of livestock management such as digging out and damming of pools to form stock ponds have had some negative impact.