National Geographic : 1952 Jan
139 Tarascan Boys, Playing Volcano, Start an Eruption by National Geographic Photographer Justin Locke Puffing Through a Pipe This toy cone is built of ash spewed out from Paricutin, the volcano that burst out of a Mexican cornfield in 1943. Since that year it has grown to a height of 1,500 feet (page 116). "To reach new stores of ore, we have had to go down deeper and deeper, until some mines now are nearly two miles deep. Below that, heat and pressure make mining diffi cult and expensive. "But even if some metals become seriously depleted, we can replace them for many pur poses with plastics, glass, fiber glass, ceramics, laminated materials, and plywoods." Forecasting Earth's Future Many geologists believe there are still plenty of mineral resources left in the upper two miles of the earth's crust. All the continents have essentially the same rock structure, and in all of them, presumably, Nature has placed supplies of ore in about the same proportions, just as in the case of oil. What about Earth's more distant future? For countless millions of years more, scien tists say, our planet will go on very much as now. As long as the supply of internal heat holds out, new mountain ranges will continue to push up as the old ones are eroded down. But at last the supply of internal heat will fail, putting an end to the building of new mountains. Rain, wind, frost, and growing things will wear down existing elevations until all the land is merely a flat, monotonous plain, barely above sea level. Possibly the sun may get hotter and burn up all earthly life. It might even explode, as other stars do occasionally, and melt all the planets in the resulting wave of heat sweeping out through millions of miles of space. More likely, astronomers say, the sun even tually will run out of hydrogen, the fuel that keeps it shining, and its heat will fail. When that takes place, life on Earth will end, unless in the meantime we've found some other way to keep going. Our frozen planet, however, will continue to swing on through its orbit around the dying sun, still held by the force of gravitation. "How long before this will happen?" I asked an astronomer friend. He laughed. "It's too far off for anyone to worry about in the foreseeable future. "Once, after an astronomy lecture, an old lady asked the speaker how long he had said it would be before the sun stopped shining. " 'About ten billion years, madam,' he re plied. " 'Oh, I'm so relieved,' she said. 'I thought you said ten million!'"