Save. Jupiterimages/Photos.com/Getty Images. It's easy to mistake lichens as the cause of tree or branch death because they tend to grow on sick trees. In fact, the reason they turn up is because a sick tree has a thin canopy and lets in the sun that makes lichens grow.ave. Jupiterimages/Photos.com/Getty Images. It's easy to mistake lichens as the cause of tree or branch death because they tend to grow on sick trees. In fact, the reason they turn up is because a sick tree has a thin canopy and lets in the sun that makes lichens grow.
4 Hoover Dam. Hoover Dam is one of the world's great engineering marvels. This massive structure, completed in 1935, crosses the Colorado River, linking Arizona and Nevada. It is 726 feet high and 1,244 feet long. Lake Mead, held back by the Hoover Dam, is the largest artificial lake in the United States. It is 110 miles long, and holds the equivalent of two years of flow of the Colorado River.
Skordas says the new turbines should function well even if the Â­water elevation falls to 305 meters above sea level, far below the historical Â­average of 358. Lake Mead, however, was already down to 337 meters in late August, when power capacity at Hoover Dam was at 1735 megawatts, down from a full capacity of 2074 MW.