Concave bridges and melting highways may sound apocalyptic, but Brooklyn-based artist Clement Valla spotted them one day on Google Earth. The irregularities arise from the process Google uses to make its maps, which combines satellite and airplane photography with 3-D models of terrain. When those models exclude man-made structures, the results can be topographical glitches, like these pictured above. The amount of distortion depends on the angle the image was shot from and the depth of the natural landscape. As Google udpates its mapping data, the anomalies correct themselves. The ephemeral images, which Valla collects in a continuing series called "Postcards from Google Earth," speak to our age-old desire to measure the world and, simultaneously, evade detection. A Google spokeswoman tells us that its "views of the Earth can sometimes appear patchy - but one man's patch is another man's treasure."