UNIT 35The Formation of Landforms

and Landscapes

Figure 35.1 A landscape in the Rocky Mountains of Colorado, shaped by glaciers, mass movements, and flowing water. The mountains in the background are landforms, as is the ridge in the foreground, which is a moraine (a ridge of debris deposited at the edge of a glacier that existed here in the past).

Figure 35.2 Where water stands on this bare granite surface after rain, weathering breaks the rock down into gravelly debris and dissolved material. The weathering products will remain here unless removed by erosion, in this case by water washing the debris off the rock along the small channel in the foreground.

Figure 35.3 A landslide closed the American River Bike Trail near Sacramento, California, in 1985. Heavy rains and floods waterlogged the soil, resulting in the collapse of slopes throughout the area.

Figure 35.4 The Chang Jiang (Yangtze River) in China originates deep in the Asian interior and flows across the heart of the country to the Pacific Ocean. In the process, it has sculpted numerous dramatic landforms, but perhaps none as scenic as the famous Three Gorges. Now the Chinese government has built a massive dam and flood control system that partially drowned the gorges seen here, forever changing the local (and regional) hydrography and altering human-environment relationships that have prevailed here for millennia.

Figure 35.5 Stream system in its drainage basin. The main river is built up by the smaller tributary streams that empty into it.

Figure 35.6 In desert environments, the wind often forms dunes from loose sand released by rock weathering or deposited by streams. These massive dunes form part of the coastal Namib Desert between Namibia’s mountains (seen in the background) and the South Atlantic Ocean behind the photographer.

Figure 35.7 “Oregon’s coastal Route 101 provides some magnificent scenery and many superb field examples of coastal landforms. Drive it southward, so you are on the ocean side! Ample rainfall in this Csb environment sustains luxuriant vegetation. Below, the waves do their work even as tectonic forces modify the geology. Here, two natural bridges have formed following wave penetration of a fault-weakened section of the coastline, the waters rushing in through one and out through the other.”

Figure 35.8 A gently sloping mountain summit in the Wind River Range, Wyoming. Using cosmogenic radionuclides, geomorphologists Eric Small and Robert Anderson estimated that summits like this are lowered by erosion at rates of 10 m (3 ft) per million years. The erosion rates of valleys below this summit are probably quite a bit higher because they are periodically eroded by glaciers (Small and Anderson, “Pleistocene relief production in Laramide mountain ranges, western United States,” Geology 26: 123–126, 1998).