Word: crust
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Hurtling through the atmosphere at nearly 70 km per sec. (150,000 m.p.h.), the giant comet struck with catastrophic force, punching a hole some 40 km (25 miles) deep through the earth's crust and into the mantle. The violence of the collision 65 million years ago completely vaporized the 8-km-wide (5 miles) comet and blasted out a tremendous crater. Huge rocks, hurled high into the + air, rained down for hundreds of kilometers. A great fireball rose above the atmosphere, carrying with it vast amounts of pulverized debris...
...Alvarezes analyzed this clay in the late 1970s and showed it had a far higher content of the rare element iridium than ordinarily found in the earth's crust. It was this discovery that led Luis Alvarez to his momentous - insight. Comets and asteroids have high iridium content, he reasoned, and the clay layer could have been formed by the worldwide fallout of the material vaporized when an errant asteroid or, as most scientists now suspect, a giant comet smacked into the earth...
...volcanoes clustered along the Ring of Fire are more dangerous. The ring traces a geologically active zone where sections of the earth's crust, known as plates, are colliding. Generally the weaker oceanic plates are forced beneath the thicker continental slabs. The friction of grinding rock, combined with heat welling up from the earth's interior, transmutes the lower edge of the oceanic plate into magma. Thick with silica, this type of magma tends to solidify near the surface, forming domes and plugs that seal off the channels through which the magma rises. Such blockages turn a volcano into...
...Although many think of it as a lifeless place, the desert is actually a teeming, though fragile, ecosystem. Home to a variety of spiders, snakes and scorpions as well as larger creatures like camels, sheep and gazelles, it is literally held together by microorganisms, which form a thin surface crust. This crust catches the seeds of sparse shrubs and prevents surface soil from blowing away. Once it is disturbed -- by the maneuvers of a million soldiers, say -- recovery can take decades. The Libyan desert still shows tank tracks laid down in World...
...private Paley appears even less admirable. An inveterate social climber, he downplayed his Jewish heritage in a quest for acceptance by the Wasp upper crust. Despite two beautiful and socially accomplished wives, he chased women relentlessly. He was aloof with employees, cold to his children and lavish in his personal life-style. "Paley," says Smith, "was as spoiled as a man could...