The green vegetation is a result of groundwater discharging out of the hillsides. Non-native or invasive plant species are proliferating on the hillsides. These are a special type of aquifer called "Perched Aquifers". They are named this because they are 'perched' higher in elevation (about 400 feet) above the regional aquifer. The regional aquifer is located at about the same elevation of the Snake River. The sediments on the hillside become saturated with water until they break loose and a landslide develops.