Earth's Resources
Resource classification
Earth's resources are grouped as renewable (replenished on human timescales, such as solar, wind, and sustainably managed biomass) and non-renewable (formed over geological timescales, such as coal, oil, gas, and most metal ores). A crucial distinction is between a resource (a concentration that may be exploitable) and a reserve (the portion proven and economically recoverable at current prices and technology). Reserves change with price and technology even when the resource does not.
Concepts to master
Understand ore grade, cut-off grade, and concentration factor - the enrichment relative to average crustal abundance that makes extraction worthwhile. Know the formation settings of major deposits: magmatic segregation (chromite, platinum), hydrothermal veins (gold, copper), sedimentary basins (coal, oil, gas), evaporites (salt, gypsum), and placer deposits. For energy, compare energy density, capacity factor, and lifecycle emissions across fossil fuels, nuclear, and renewables. Consider environmental impacts: acid mine drainage, subsidence, tailings, groundwater contamination, land use, and greenhouse gas release. Apply sustainable development ideas: recycling, substitution, efficiency, and the circular economy.
Common traps
Many students equate 'resource' with 'reserve' and assume reserves are fixed. Others ignore that renewable does not mean impact-free (wind and solar have land and material costs). Questions may ask for the most sustainable option in context - read the constraints (cost, location, scale) before choosing.
Worked example
If a deposit contains 2% copper and average crust is 0.006%, the concentration factor is 2 ÷ 0.006 ≈ 333. A high factor indicates an enriched, potentially economic deposit, but economics still depend on extraction cost and market price.