Today we find ourselves in the Utah dessert near a town called Moab. It's quite a place, during the summer the temperatures can exceed 40 °C (100 °F) while in the winter months the thermometer can sink as low as -30 °C (-24 °F). With an average yearly rainfall of 238.9 mm, it can officially be classified as a desert. The last thing you could associate with such an harsh environment is fertility but that might be exactly what we would find here. The purple lakes you can see on the image of today resemble a so called 'potash' mine. Potash is another name for potassium chloride, a widely used fertilizer, especially to enhance water movement through plant stems. Pretty ironic to mine such a fertilizer in the middle of desert, no?
Those purple lakes might not look like what we would call 'a mine'. Originally, the mine was a network of caves and shafts but after a collapse took the lives of 25 mineworkers, the company introduced a new way of mining. The purple lakes are located near a river as you can see, and that river seems to be very essential. They deviate the water from the river into the old mine shafts where the potash containing minerals are dissolving into the water. The water, containing the soluted potash, is pumped up again, up to the surface. There, it is stored in the different open air lakes, being exposed to the intensive sunlight. The water evaporates while the potash remains in the lakes where it can easily get collected. To speed up this process, they add a blue dye to the water, lowering its' albedo so the evaporation process takes place even faster!
Pretty fascinating, no? I added some other pictures, on different moments in time. This way, you can see the evolution from the moment they just put the dye in it up to later in the evaporation process.
© Google Earth/Copernicus/ USGS / US farm service agency
source information: wikipedia <3