Goldstrike mine in northeastern Nevada is one of the largest gold mines in the world. In 2016, the mine produced 1.1 million ounces of gold. Only two other operations—the Grasberg mine in Indonesia and the Muruntau mine in Uzbekistan—produced more.
On September 25, 2016, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite captured this false-color image of the mine. Vegetation appears red. Water is dark blue. Bare rock appears in shades of brown and gray. The most noticeable feature is the Betze-Post open-pit mine, which is managed by Barrick Gold Corporation and has a depth of more than 500 meters (1,600 feet). Smaller open-pit mines operated by other companies are also visible northwest and southeast of the Betze-Post pit.
Trucks transport ore from the bottom of the pit to nearby processing facilities, where gold is concentrated and extracted. On average, there is roughly 0.1 ounce of gold per ton of ore. Processing typically involves crushing ore into powder, exposing it to high temperatures and pressures, and leaching material out of liquid slurries. Leftover slurry is stored in tailing ponds, where solids settle out. In addition to its large open-pit mine, Goldstrike has two underground mines that also produce ore.
One of the key issues facing mines is water management. Open-pit mining requires pumping groundwater out of adjacent aquifers in order to prevent the pit from flooding. At Goldstrike, operators pump several thousand gallons of groundwater per minute to keep the water table below the level of the pit. Some of this water is used to process ore, but some of it gets used in other ways or pumped backed into the ground. For instance, the water used to irrigate the circular fields southwest of the Betze-Post pit comes from groundwater pumping related to the mining.
While the company that operates Goldstrike mine maintains a network of monitoring wells and stream gauges to track how mine activities are affecting the aquifer, it also has used Interferometric synthetic aperture radar (InSAR) data from satellites as part of its monitoring efforts. Since each monitoring well can cost between $300,000 to $500,000, and InSAR offers a big-picture view of the aquifer, a satellite perspective can offer an effective way of monitoring subsidence, uplift, and other changes in the Earth’s crust associated with groundwater pumping, the company noted. InSAR observations show subsidence in areas near the mines and uplift in areas southwest of the mines.
NASA Earth Observatory image by Jesse Allen, using data from NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team. Story by Adam Voiland.