Page 483 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 14 Weathering, Karst Landscapes, and Mass Movement 447
(a) Large 2013 landslide within Bingham Canyon Mine outside Salt Lake City, Utah.
and selenium that generally exceed government standards.
Scientists have made informal, but impressive, quantitative comparisons between scarification and natural denu- dation processes. Geologist R. L. Hooke used estimates of U.S. excavations for new housing, mineral production (including the three largest types— stone, sand and gravel, and coal), and highway construction. He then prorated these quantities of moved earth for all countries, based on their gross domes- tic product, energy consumption, and agriculture’s effect on river sediment loads. From these, he calculated a global estimate for human earth moving. Later researchers confirmed and expanded on these findings.
Hooke estimated for the early 1990s that humans, as a geomorphic agent, annually moved 40–45 billion tonnes (40–45 Gt) of the planet’s sur- face. Compare this quantity with the natural movement of river sediment (14 Gt per year), or the movement due to wave action and erosion along coast- lines (1.25 Gt per year), or deep-ocean sedimentation (7 Gt per year). In 2005, geologist Bruce Wilkinson corrobo- rated these measurements, concluding that humans are 10 times more active in shaping the landscape than natural processes. As Hooke concluded about humans,
Homo sapiens has become an impressive geomorphic agent. Coupling our earth-moving prowess with our inad- vertent adding of sediment load to rivers and the visual impact of our activities on the landscape, one is compelled to acknowledge that, for better or for worse, this biogeo- morphic agent may be the premier geomorphic agent of our time.*
*R. L. Hooke, “On the efficacy of humans as geomorphic agents,” GSA Today (The Geological Society of America), 4, 9 (September 1994): 217–226.
(b) Kalgoorlie Super Pit, a massive open pit gold mine in Western Australia.
▲Figure 14.29 Scarification. [(a) Ravell Call/AP Photo. (b) Nuttapol Chavanavanichwoot/123RF.]
for mining and burying the stream channels. Moun- taintop removal in West Virginia, and elsewhere in the region, has flattened more than 500 mountains, removing an estimated half a million hectares and fill- ing some 200 km of streams with tailings. These valley fills affect downstream water quality with concentra- tions of potentially toxic nickel, lead, cadmium, iron,
Georeport 14.5 open pit mining in the Amazon Region
The Carajás Mine in northern Brazil is the world’s largest iron ore mining complex. Since the 1980s, open pit mining operations at Carajás have destroyed large tracts of rain forest, causing runoff of sediment and pollutants into streams, and triggered intense conflict over land with indigenous communities. According to 2009 estimates, the region contains 7.2 billion
tonnes of iron ore reserves. For a satellite image of the pit, go to earthobservatory.nasa.gov/IOTD/view.php?id=39581.