Earthshots: Satellite Images of Environmental Change

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» Kalgoorlie, Western Australia

In a remote part of the Western Australia outback lies one of the world’s largest holes in the ground. Known as the Super Pit, the Fimiston Open Pit is part of what is known as the Golden Mile, where gold has been mined continuously since 1893. The mine sits right next to Kalgoorlie-Boulder, a city of about 33,000 located almost 600 kilometers from Perth.

The first gold rush here occurred around 1890. The easy-to-reach gold is gone, but small pieces and flakes remain. Work on the Super Pit began in 1989, and now at least 800,000 ounces of gold are dug out of the mine every year. According to the USGS Minerals Commodity Summaries (2018), Australia is the second largest gold producer in the world, after China.

Getting at the gold requires removing large amounts of ore. Hence, the gaping hole in the ground next to Kalgoorlie. Surrounding Kalgoorlie and the mine, sparse vegetation is represented by the beige and reddish colors.

Like much of Western Australia, the region surrounding Kalgoorlie and the Super Pit experiences hot summers and cool winters. The water bodies seen in the images south of Kalgoorlie and in the upper left are semi-dry salt lakes. On the eastern side of the Super Pit are the Fimiston Mill, where the ore is processed, waste dumps, and tailings ponds, which appear in the images as gray or white.

Map of the featured area.

The Super Pit, the largest open-pit gold mine in Australia, is currently 2 miles long, a mile wide, and 2,000 feet deep. By 2021, it’s expected to measure 2.2 miles long, a mile wide, and up to 2,300 feet—nearly half a mile—deep.

Active 24 hours a day, 7 days a week, huge trucks haul over 200,000 tons of rock and dirt out of the pit every day. The ore is crushed and water added to form a mud-like slurry, which is pumped to flotation cells. Air is added to the slurry and a froth forms on the surface, which contains all of the gold. The waste is called tailings and is discharged into ponds, visible as the polygons east and north of the Super Pit in the Landsat images.

Large quantities of ore need to be moved to get to the gold. This is done with blasting, but with Kalgoorlie-Boulder so close to the mine, techniques are used to minimize the impact of the blasting on the population. Blasting is generally done only at certain times of day, and wind direction and speed are considered before a blast. Additionally, smaller blasts are used, a strategy that takes more time to remove the desired amount of rock, but minimizes dust, vibration, and “fly rock.”

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