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1. Deserts: Geology and Resources – A. S. Walker Approximately one–third of the Earth's land surface is desert, arid land with meager rainfall that supports only sparse vegetation and a limited population of people and animals. Deserts—stark, sometimes mysterious worlds—have been portrayed as fascinating environments of adventure and exploration from narratives such as that of Lawrence of Arabia to movies such as "Dune." 2. Earthquakes – Kaye M. Shedlock & Louis C. Pakiser One of the most frightening and destructive phenomena of nature is a severe earthquake and its terrible aftereffects. If the earthquake occurs in a populated area, it may cause many deaths and injuries and extensive property damage. Today we are challenging the assumption that earthquakes must present an uncontrollable and unpredictable hazard to life and property. Scientists have begun to estimate the locations and likelihoods of future damaging earthquakes. Sites of greatest hazard are being identified, and definite progress is being made in designing structures that will withstand the effects of earthquakes. 3. Eruptions of Mount St. Helens: Past, Present, and Future – Robert I. Tilling, Lyn Topinka, and Donald A. Swanson May 18, 1980. On that fateful day, Mount St. Helens Volcano in Washington exploded violently after two months of intense earthquake activity and intermittent, relatively weak eruptions, causing the worst volcanic disaster in the recorded history of the United States. The cataclysmic eruption and related events on May 18 rank among the most significant geologic events in the United States during the 20th century. 4. Geologic Time – William L. Newman The Earth is very old — 4.5 billion years or more — according to recent estimates. This vast span of time, called geologic time by earth scientists, is difficult to comprehend in the familiar time units of months and years, or even centuries. How then do scientists reckon geologic time, and why do they believe the Earth is so old? A great part of the secret of the Earth's age is locked up in its rocks, and our centuries–old search for the key led to the beginning and nourished the growth of geologic science. 5. The Interior of the Earth – Eugene C. Robertson Three centuries ago, Sir Isaac Newton determined that the average density of the Earth is twice that of surface rocks and that the Earth's interior therefore must be composed of much denser material. Our knowledge of what's inside the Earth has improved immensely since Newton's time, but his estimate of the density remains essentially unchanged. This brochure presents current information on what makes up the interior of our planet. 6. Our Changing Continent – John S. Schlee Where were the land areas and oceans of the North American Continent one million years ago, compared to their present locations? Was North America always about the same size and shape that it is today? To answer these questions, geologists must interpret the clues they find preserved in the rocks. 7. The San Andreas Fault – Sandra S. Schulz and Robert E. Wallace Scientists have learned that the Earth's crust is fractured into a series of "plates" that have been moving very slowly over the Earth's surface for millions of years. Two of these moving plates meet in western California; the boundary between them is the San Andreas fault. 8. The Severity of an Earthquake – Anonymous Earthquakes are the result of forces deep within the Earth's interior that continuously affect the surface of the Earth. The energy from these forces is stored in a variety of ways within the rocks. When this energy is released suddenly, for example by shearing movements along faults in the crust of the Earth, an earthquake results. The severity of an earthquake can be expressed in terms of both intensity and magnitude. However, the two terms are quite different, and they are often confused. 9. Volcanoes – Robert I Tilling This booklet presents a generalized summary of the nature, workings, products, and hazards of the common types of volcanoes around the world, along with a brief introduction to the techniques of volcano monitoring and research. 10. Volcanoes of the United States – Steven R. Brantley The United States ranks third, behind Indonesia and Japan, in the number of historically active volcanoes (that is, those for which we have written accounts of eruptions). In addition, about 10% of the more than 1,500 volcanoes that have erupted in the past 10,000 years are located in the United States. Most of these volcanoes are found in the Aleutian Islands, the Alaska Peninsula, the Hawaiian Islands, and the Cascade Range of the Pacific Northwest; the remainder are widely distributed in the western part of the Nation. A few U.S. volcanoes have produced some of the largest and most dangerous types of eruptions in this century, while several others have threatened to erupt. |
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