Geography of Colorado
The Rocky Mountains within Colorado contain 54 peaks that are 14,000 feet (4270 m) or higher, known as fourteeners. The mountains are timbered with conifers and aspen to the tree line, at an elevation of about 12,000 feet (3,650 m) in southern Colorado to about 10,500 feet (3,200 m) in northern Colorado; above this only alpine vegetation grows. The Rockies are snow-covered only in the winter; most snow melts by mid-August with the exception of a few small glaciers. The Colorado Mineral Belt, stretching from the San Juan Mountains in the southwest to Boulder and Central City on the front range, contains most of the historic gold and silver mining districts of Colorado.
Earned run average
As an extreme example, pitchers for the Colorado Rockies have historically faced many problems, all damaging to their ERAs. The combination of high altitude (5,280 ft or 1,610 m) and a semi-arid climate in Denver causes fly balls to travel up to 10% farther than at sea level. Denver's altitude and low humidity also reduce the ability of pitchers to throw effective breaking balls, due to both reduced air resistance and difficulty in gripping very dry baseballs. These conditions have been countered to some extent since 2002 by the team's use of humidors to store baseballs before games. These difficult circumstances for Rockies pitchers may not adversely affect their win-loss records, since opposing pitchers must deal with the same problems. Indeed, hometown hurlers have some advantage in any given game since they are physically acclimated to the altitude and often develop techniques to mitigate the challenges of this ballpark. Still, conditions there tend to inflate Rockies' ERAs relative to the rest of the league.