Ridge lift is upward moving air which results from wind blowing into a steep ridge or cliff. Hawks, vultures, and pilots of sailplanes, hang gliders, and paragliders all use ridge lift to soar - to gain or maintain altitude when flying. The birds are able to conserve energy by not flapping, and the gliders are able to stay aloft without any mechanical power source. As long as the air near the ridge is rising faster than the glider's sink rate (gliders are always sinking through the air) the glider can climb - typical climb rates are 100 to 1000 FPM (feet per minute). The soarable envelope extends a distance above and in front of the ridge proportional to the strength of the wind. Ridge soaring can provide many hours of relatively easy flying. Coastal bluffs tend to provide reliable ridge lift in spectacular settings, making them particularly popular with soaring enthusiasts of many species