What was the name of the area that had upward movement of magma under it?
The creation of Mono Basin National Forest Scenic Area in 1984 stopped any further geothermal prospecting. Mono Basin was the first National Scenic Area in the United States. It offers more protection than other United States Forest Service lands, surrounds Mono Lake and its two volcanic islands, Black Point, Panum Crater and much of the northern half of the Mono Craters. Litigation and outreach by the Mono Lake Committee, the National Audubon Society and other conservation groups has helped to slow water diversions from tributaries feeding Mono Lake.A series of earthquakes inside Long Valley Caldera, coincidentally starting two weeks after the May 1980 eruption of Mount St. Helens in Washington, alerted geologists to the possibility of renewed volcanic activity in the region. Four magnitude 6 earthquakes struck the southern margin of Long Valley Caldera in an area that was close to the Mono–Inyo fissure system. The caldera floor had also uplifted by 10 inches (30 cm) in five years. Upward movement of magma under the caldera was thought to be the cause of the earthquakes and uplift.Persistent earthquake swarms in 1982 prompted the United States Geological Survey (USGS) to issue a "potential volcanic hazard" notice for Long Valley. That same year, permanent monitoring of the area by the Long Valley Observatory started. The hazard notice was lifted in 1984 after USGS scientists concluded that magma had been injected into fissures below Mammoth Mountain but had congealed underground. From 1990 to 1996, 150 acres (60 ha) of trees were killed on Mammoth Mountain by 20% to 95% concentrations of carbon dioxide (CO2) in the soil (less than 1% is normal). Chemical analysis of the CO2 indicated it was derived from magma.
Long Valley Caldera