By Barnes, Sherry
E Magazine , Vol. 11, No. 4
Explorations of Gravel Mining, the Antarctic Shelf and `Natural' Cleansers
What are the environmental impacts of gravel extraction?
--Kristina Hayward, Berkshire, UK
Gravel extraction, often in stream beds, is big business in the United States and elsewhere, and there's a definite environmental cost. Gravel is used in the construction of patios, parking lots, roads and buildings. A geologic report by Ohio's Department of Natural Resources (DNR) recorded a combined sales total of over 57 million tons of sand and gravel for that state alone in 1997.
Extraction of gravel in streams and rivers results in sediment-related pollution and a disturbance of natural hydraulic patterns. Carl Mount, senior environmental protection specialist of the Division of Minerals and Geology, Colorado DNR, notes that although the state has 75 in-stream extraction operations, "It's not being done as much. The river is a hassle to deal with--and it's expensive." He explains that most operations now mine the floodplains next to streams or "build a diversion so the stream flows around the area they're mining"--a practice that is in itself disruptive. Peter Dobbins, director of Friends of the Garcia River, says his California-based group successfully fought off a mining proposal because "in-stream gravel extraction ruins water quality and destroys habitat for fish, reptiles and birds." CONTACT: Friends of the Garcia River, (707) 882-3086, www.frog.org; United States Geological Service, http:// minerals.usgs.gov.
What are the implications of the large iceberg (I heard the size of Jamaica) that disconnected from Antarctica? --Gaertner Olivier, Brussels, Belgium
According to The National Snow and Ice Data Center (NSIDC), the ice sheets of Antarctica are huge, floating platforms of ice that are grounded by the Antarctic continent and islands in the region. Snow, glaciers and ice flows feed these large ice sheets in the colder months. In warmer periods, surface melting and the breaking off (calving) of icebergs decrease the mass.
The iceberg in question was named "B-15" by the National Ice Center, a governmental organization that tracks icebergs for vessel safety. B-15, which is 170 miles long and 25 miles wide, calved from the Ross Ice Shelf in March 2000, its mass converts to about 3.2 trillion tons of fresh water and approximates Maryland in length.
This vast amount of water has a surprisingly neutral effect on sea levels. Dr. Ted Scambos, a research associate scientist at the University of Colorado, explains, "Since an iceberg floats in ocean water, and much of it is below the surface, it is already displacing the same volume of water it will contribute when it eventually melts. …