Word: occurs
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Dates: during 1980-1989
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Fusion, the nuclear reaction that powers the sun, was originally thought to occur only at extremely high temperatures and pressures...
...Pons and Fleischmann claimed that their device--in which electricity was sent through a jar of heavy water and a palladium electrode at room temperature--produced additional heat, which could only occur if the heavy hydrogen atoms in the water fused together...
...city the size of Cambridge, this situation is unacceptable. Violent crimes occur here every day--for example, one shuttle bus driver recently was accosted after parking his bus near the Business School. Unless the University does something to address a growing security problem, it is only a matter of time before the next student is mugged, assaulted or raped...
...earth is constantly moving underfoot. Its surface, cracked like ancient pottery, is broken into 15 large pieces. These pieces of crust, called plates, restlessly roam about, driven by plumes of molten rock that roil up from the planet's superheated core. Many of the world's largest earthquakes occur at the boundaries of such plates. The San Andreas fault system divides the Pacific plate and the North American plate, which grind past each other at the pace of 2 in. a year. But this movement of the plates is not uniform. Along fault zones the plates tend to become "locked...
...earthquakes are understood, accurate prediction of their occurrence has remained beyond reach. Earthquake forecasting is mostly based on past history. If a fault once generated a big earthquake, it can be assumed that it will do so again. But just where and when will the next big break occur? Here scientists are beginning to make headway. Geophysicist Wayne Thatcher of the USGS notes that the 1906 quake ruptured a 260-mile-long section of the San Andreas, extending from Cape Mendocino to San Juan Bautista. But the plate movement along the southern portion of the rupture was minor compared with...