The making of a mountain: journey to the Himalayas and discover what happens when continents collide. (Earth Science Geology).Fifty years ago, on May 29, 1953, mountain climbers Edmund Hillary and Tenzing Norgay Tenzing Norgay (born May 15, 1914, Tshechu, Tibet [now Tibet Autonomous Region, China]—died May 9, 1986, Darjeeling [now Darjiling], India) Tibetan Sherpa mountaineer. became the first humans ever to scale the icy summit of Mount Everest (elevation 29,035 feet), the world's highest peak. Since then, more than 1,500 other adventurers have reached this pinnacle in the Himalayan mountain range, which sprawls 2,550 kilometers (1,600 miles) along the border of India and Tibet. And at least 170 people have died while attempting the climb. If a mountain is a landform land·form n. One of the features that make up the earth's surface, such as a plain, mountain, or valley. landform A recognizable, naturally formed feature on the Earth's surface. standing 300 m (1,000 ft) above sea level, then Mount Everest is a towering giant. It stands 8.85 kilometers (5.5 mi) high--roughly the cruising altitude A level determined by vertical measurement from mean sea level, maintained during a flight or portion thereof. of a modern jet. But Everest isn't a lone giant: At least 30 Himalayan peaks soar 7.4 km (4.6 mi) high. And geologists say the entire mountain range is rising at a rate of about 5 millimeters (0.2 inches) a year--because the natural forces that thrust the mountains up 40 million years ago are still churning today. That makes the Himalayas themselves almost as dynamic as the thrill-seekers who ascend them. Turn the page and check out the geologic action. BUILDING THE HIMALAYAS Mountain building-or orogenesis-occurs when Earth's crustal plates (see map, below) move. The Himalayas formed when plate movement drove the continent of India into southern Asia about 40 million years ago (MYA). Instead of grinding to a halt, India plowed on. The result: Earth's crust buckled and folded, the way metal crumples when two cars collide. Over millions of years, layers of warped rock evolved into mountains. (1) TECTONIC PLATES This is a list of tectonic plates on Earth. Tectonic plates are pieces of the Earth's crust and uppermost mantle, together referred to as the lithosphere. The plates are around 100 km (60 miles) thick and consist of two principal types of material: oceanic crust (also called Earth's crust, the planet's solid outer shell, rides on a rocky, partially molten layer, or mantle. Together, these two layers form the lithosphere lithosphere (lĭth`əsfēr '), brittle uppermost shell of the earth, broken into a number of tectonic plates. The lithosphere consists of the heavy oceanic and lighter continental crusts, and the uppermost portion of the mantle. . More than 100 km (62.1 mi) thick, the lithosphere is somewhat flexible like taffy Taffy Welshman who “stole a piece of beef.” [Nurs. Rhyme: Baring Gould, 72–73] See : Thievery , yet at the same time strong enough to form semi-rigid tectonic plates. About 15 of these thick slabs cover Earth's surface Noun 1. Earth's surface - the outermost level of the land or sea; "earthquakes originate far below the surface"; "three quarters of the Earth's surface is covered by water" surface . Continents are embedded in the plates, which ride on the elastic mantle, jostling to and fro to and fro adv. Back and forth. to and fro Adverb, adj also to-and-fro 1. like rafts on a stormy sea. [ILLUSTRATION OMITTED] (20) HISTORY OF THE HIMALAYAS CONTINENTAL COLLISION
Geologists believe a sea once separated the continental land-masses of India and Asia. Over 30 million years' time, India drifted north at a rate of 9 meters (29.5 feet) per century, until it struck the southern edge of Asia. The collision crumpled crum·ple v. crum·pled, crum·pling, crum·ples v.tr. 1. To crush together or press into wrinkles; rumple. 2. To cause to collapse. v.intr. 1. layers of rock into giant mountains. [ILLUSTRATION OMITTED] 60 Million Years Ago (MYA) India strikes the Asian plate and keeps driving northward. This movement starts to close up the Tethys Sea. As the continental plates ram against each other, Earth's crust squeezes upward. [ILLUSTRATION OMITTED] 40 MYA As the Indian plate The India or Indian Plate is a minor tectonic plate. It was originally a part of the ancient continent of Gondwanaland from which it split off, eventually becoming a major plate. About 50 to 55 million years ago, it fused with the adjacent Indo-Australian Plate. drives under Asia, lightweight sedimentary rock sedimentary rock: see rock; sediment. sedimentary rock Rock formed at or near the Earth's surface by the accumulation and lithification of fragments of preexisting rocks or by precipitation from solution at normal surface temperatures. (made of compressed dirt, sand, and silt) at the bottom of the Tethys Sea crumples into folds of all shapes and sizes. [ILLUSTRATION OMITTED] 20 MYA The sea disappears. As India keeps squeezing beneath Asia, rocks scrape and buckle off India's crust, building up a folded mountain range, now called the Himalayas. [ILLUSTRATION OMITTED] 3. HIMALAYAS TODAY Geologists say the Indian plate continues to squeeze northward under the Asian plate at a rate of 18 millimeters a year. As a result, the Himalayas--including Everest--are rising about 5 mm a year. The very tops of many Himalayan peaks consist of sedimentary rocks (Geol.) See See also: Sedimentary from the ancient Tethys Sea. [ILLUSTRATION OMITTED] 4. FOLDED MOUNTAINS As continents collided, the oceanic crust oceanic crust See under crust. forced itself under the less dense continental crust continental crust See under crust. . It was flexible enough to buckle and fold instead of break. The crustal crust·al adj. Of or relating to a crust, especially that of the earth or the moon. Adj. 1. crustal - of or relating to or characteristic of the crust of the earth or moon folds range from tiny wrinkles wrinkles See bells and whistles. to formations miles high. Geologists use many terms to describe folded rock. Two main types: anticlines, arch-shape upward folds, and synclines, bowl-shape downward folds. [ILLUSTRATION OMITTED] HANDS-ON SCIENCE Mountain-Making YOU NEED * modeling clay in three colors * construction paper (30 X 15 cm) * rolling pin * ruler * butter knife * a partner TO DO 1. With each color clay, roll out two 0.5 centimeter-thick slabs, Make a total of six clay slabs, and trim each one into a 30 X 30-cm square. 2. Use ruler and knife to slice each square slab into a 30 X 15-cm rectangle, 3. Make two stacks of 6 slabs each; alternate colors. Gently press slabs together; each stack should be no more than 3-cm thick. Place each slab on a sheet of construction paper. These represent the Indian and Asian plates. 4. One partner should slide the "Indian Plate" slowly toward the "Asian Plate," which the other partner holds firmly in place. PREDICT: What will happen when the plates meet? 5. Keep gently but steadily pushing India into Asia, until the clay has crumpled. What kinds of folds have you made? COMPARE your clay models to the "Types of Folds" diagram, at right. THINK ABOUT IT What might happen if your continental-plate models were made of dry lasagna noodles noo·dle 1 n. A narrow, ribbonlike strip of dried dough, usually made of flour, eggs, and water. [German Nudel. instead of clay? Did You Know? * When stress is applied to rocks, they deform elastically. When the stress exceeds the rocks' elastic limits, they deform by folding or breaking. * The path to the top of Mount Everest is so well traveled that some climbers say the mountain is becoming the world's highest junkyard. Since the first successful expedition to the top in 1953, at least 50 tons of empty oxygen bottles and other trash has piled up. Fortunately, teams now make trash-collecting climbs. * Geologists have used clay for more than a century to create models of Earth's rock layers on a scale small enough to experiment on. Cross-Curricular Connection Social Studies: The people of Nepal call Mount Everest Sagarmatha. Find out more about Nepal and the people who live in this remote nation high in the Himalayas. Then construct charts and graphs to present facts and figures about the country, such as population, climate, land area, average altitude, longest river, highest mountain. Critical Thinking: Everest grows about 5 mm taller each year. If it continues to grow at this rate, how tall will it be in 100 years? 1,000 years? 1 million years? 10 million years? Resources Within Reach: My Everest Story, by Mark Pfetzer, Dutton, 1998. (At age 16, Pfetzer became the youngest person to climb Everest.) Check out the PBS/NOVA special "Everest" online" at www.pbs.org/wgbh/nova/everest "Taking a Mountain's Measure," by R. Monastersky, Science News, Jan. 1, 2000 CHECK FOR UNDERSTANDING Directions: For 1 to 7, match the word in the left column with the correct phrase in the right column. Then circle the correct word(s) to complete the last sentence. --1. crust a. bowl-shaped downward fold in crust --2. mantle b. mountain building --3. syncline c. crustal fracture --4. anticline d. planet's solid outer shell --5. lithosphere e. partially molten Earth layer --6. fault f. Earth's top two outer layers --7. orogenesis g. arch-shaped upward fold in crust 8. Geologists say the (Indian, Asian, Pacific) plate continues to squeeze northward under the (Indian, Asian, Pacific) plate at a rate of (5, 9, 15, 18) mm per year. As a result, the Himalayas are rising (5, 9, 15, 18) mm a year. ANSWERS 1. d 2. e 3. a 4.g 5. f 6. c 7. b 8. Indian, Asian, 18,5 |
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