Guiana Shield Guiana Shield The Guiana Shield is one of the three cratons of the South American Plate. It is a 1.7 billion-year-old Precambrian geological formation in northeast South America that forms a portion of the northern coast. The higher elevations on the shield are called the Guiana Highlands, which is where the table-like mountains called tepuis are found. The Guiana Highlands are also the source of some of the world's most spectacular waterfalls such as Angel Falls, Kaieteur Falls and Kuquenan Falls. The Guiana Shield underlies Guyana (previously British Guiana), Suriname (previously Dutch Guiana) and French Guiana (or Guyane), most of
American Falls to the north. To survey the rockfall and determine how to prevent the falls from becoming a series of rapids, the U.S. Army Corps of Engineers blocked the flow of water over the American Falls from June to November 1969. Results conflict as to whether tourist attendance that season was higher or lower than normal. Attendance increases were likely due to the news the cataract was dried off; decreases in tourists could be attributed to people believing both cataracts (the American and Horseshoe Falls) were dewatered. By December 1969, water was flowing over the American Falls again. In the mid‑1970s,