Meg Glazner, age 10, of Colorado Springs, Colo., for her question:
HOW DO THEY MEASURE MOUNTAIN PEAKS?
Mt. McKinley, with its altitude of 20,320 feet, is the highest peak in North America. It is located in the Alaska Range in Alaska. Canada's tallest peak is found in the Saint Elias range. It is the 19,850 foot Mt. Logan. Highest mountain in the world is the majestic Mt. Everest which reached up to 29,028 feet on the Nepal Tibet border in the Himalaya.
Mountains cover about one fifth of the land surface of the world.
Geologists and geographers define a mountainous area as one that lies at least 2,000 feet above its surroundings. Its land surface must be made up of long slopes, deep canyons or valleys, and high, narrow ridges.
A mountainous area, geologists add, must also include two or more zones of climate and plant life.
Surveyors measure the height of land surfaces, including mountains, by determining the distance of the land above sea level. When we say the height, or altitude, of Pikes Peak in Colorado is 14,110 feet, we mean that its highest peak, or summit, rises 14,110 feet above the level of the sea.
Actually, Pikes Peak is far inland and its top rises only about 9,000 feet above the surface of the nearby Great Plains.
A barometer is an instrument that records air pressure. The barometer and the barometric altimeter, an instrument based on the barometer, are used to measure heights. Altimeters give quick, accurate altitude readings. Most official figures for mountain heights were obtained with altimeters.
For more accurate readings, surveyors use complicated instruments and techniques based on geometry and trigonometry. With these methods, they can measure a mountain without actually climbing it. They do need to see the peak, however.
None of the methods produce complete accurate measurements. Climatic and other conditions affect all instrument readings, and so the results tend to vary slightly.
Sometimes the scientists use the geoidal method to measure mountain heights. They first locate a mountain's position on the geoid, an imaginary reference surface produced by extending the mean sea level of the oceans under the continents.
Next the scientists calculated the distance between that point on the geoid and the earth's center to determine the height of the mountain.