A world map shows high (dark blue) urban population in America, Australia, parts of the Middle East, Southeast Asia; moderate (blue) in parts of Africa, Asia, and Eastern Europe; low (light blue) in Central/South Asia, and Sub-Saharan Africa.
Class | Rank | Percent | Major Iron-Producing Areas in North America | Oil Shale or Tar Sands | Lightning Frequency | <0.1 flashes/km²/year | 0.1 flashes/km²/year | 0.2 flashes/km²/year | 0.4 flashes/km²/year | 0.6 flashes/km²/year | 0.8 flashes/km²/year | 1 flash/km²/year | 2 flashes/km²/year | 4 flashes/km²/year | 6 flashes/km²/year | 8 flashes/km²/year | 10 flashes/km²/year | 20 flashes/km²/year | 30 flashes/km²/year | Consolidated rock aquifers | Combination aquifers | Productive aquifers | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2.52% | 11.5% | 24.4% | 16.4% | 8.63% | 6.27% | 9.50% | 4.67% | 3.58% | 14.1% | 25.7% | 10.1% | 11.3% | 14.8% | 42.6% | 30.6% | 47.1% | 14.0% | 4.45% | 18.1% | ||||
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