Multiple cloud-free images collected over several years have been combined to make this picture: 1992 is shown in blue, 2000 in green, and 2010 in red. Places that had lots of light in all three years show up bright white (equal amounts of blue, green and red) -- that basically shows established cities and towns (like the Twin Cities) that haven't changed much over that time period.But whoa, check out that big patch of red in the northwest corner of North Dakota. That indicates an area of bright lights in 2010 that was dark in 2000 and 1992. What could this be? Here's a hint: a map showing the extent of the red-hot Bakken Shale oil-drilling boom that got underway a few years ago. Oil is being produced from the Bakken by drilling and hydraulically fracturing long horizontal wells.