council. For centuries, navigators of the world’s oceans have been familiar with an effect of Earth’s magnetic field: It imparts a directional preference to the needle of a compass. Although in some settings ...

AMHERST COLLEGE Department of Geology GEOLOGY 41 Environmental and Solid Earth Geophysics Instructor: Peter Crowley 542-2715 pdcrowley@amherst.edu ENMNH 310 Lectures: Lab: Text: M ...

How the Earth Works Plate Tectonic Theory Types of Plate Boundaries Driving Forces of Plate Motion Basic Premise of ...

© 2009 Allan Ludman and Stephen Marshak W.W. Norton & Company CHAPTER 2 THE WAY THE EARTH WORKS: EXAMINING PLATE TECTONICS PURPOSE To examine the evidence that led to development of the plate ...

What on Earth is PLATE TECTONICS? The Earth is covered by a thin skin of solid crust and uppermost 3) Deep within ...

America 1 2 3 4 5 6 7 8 9 10 009 06 05 04 03 02 01 Table of Contents To the Teacher Correlation of Earth Science books of the Glencoe Science Custom Curriculum Series to the National Science Standards Chapter ...

908-913 (ISSN: 2141-7016) Journal of Emerging Trends in Monitoring for Horizontal Movement in an Earth Dam Using Differential GPS 1 Jacob. O. Ehiorobo and 2Raphael Irughe-Ehigiator 1 Faculty of Engineering ...

EARTH MANUAL PART 1 THIRD EDITION U.S. DEPARTMENT OF THE INTERIOR BUREAU OF RECLAMATION EARTH MANUAL PART ...

Asteroid and comet impacts have played a major role in the geological and biological history of the Earth. It is widely accepted that one such event, 65 million years ago, perturbed the global environment so catastrophically that a major biological extinction ensued (Alvarez 1980). As a result, both the scientific community and the general populace are increasingly interested in both the threat to civilization and the potential environmental consequences of impacts. Previous papers have examined, in detail, the natural hazard associated with the major environmental perturbations caused by impact events (Toon et al. 1994, 1997). To provide a quick and straightforward method for estimating the severity of several of these environmental effects, we have developed a free-of-charge, easy-to-use Web page maintained by the University of Arizona, which is located at: www.lpl.arizona.edu/impacteffects. Our program focuses on the consequences of an impact event for the regional environment; that is, from the impact location to a few thousand km away. The purpose of this paper is to present and justify the algorithm behind our program so that it may be applied more specifically to important terrestrial impact events and its reliability and limitations may be understood. Abstract–We have developed a Web-based program for quickly estimating the regional environmental consequences of a comet or asteroid impact on Earth (www.lpl.arizona.edu/ impacteffects). This paper details the observations, assumptions and equations upon which the program is based. It describes our approach to quantifying the principal impact processes that might affect the people, buildings, and landscape in the vicinity of an impact event and discusses the uncertainty in our predictions. The program requires six inputs: impactor diameter, impactor density, impact velocity before atmospheric entry, impact angle, the distance from the impact at which the environmental effects are to be calculated, and the target type (sedimentary rock, crystalline rock, or a water layer above rock). The program includes novel algorithms for estimating the fate of the impactor during atmospheric traverse, the thermal radiation emitted by the impact-generated vapor plume (fireball), and the intensity of seismic shaking. The program also approximates various dimensions of the impact crater and ejecta deposit, as well as estimating the severity of the air blast in both crater-forming and airburst impacts. We illustrate the utility of our program by examining the predicted environmental consequences across the United States of hypothetical impact scenarios occurring in Los Angeles. We find that the most wide-reaching environmental consequence is seismic shaking: both ejecta deposit thickness and air-blast pressure decay much more rapidly with distance than with seismic ground motion. Close to the impact site the most devastating effect is from thermal radiation; however, the curvature of the Earth implies that distant localities are shielded from direct thermal radiation because the fireball is below the horizon. The formation of an impact crater is an extremely complicated and dynamic process (Melosh 1989). The abrupt deceleration of a comet or asteroid as it collides with the Earth transfers an immense amount of kinetic energy from the impacting body to the target. As a result, the target and impactor are rapidly compressed to very high pressures and heated to enormous temperatures. Between the compressed and uncompressed material, a shock wave is created that propagates away from the point of impact. In the wake of the expanding shock wave, the target is comprehensively fractured, shock-heated, shaken, and set in motion—leading to the excavation of a cavity many times larger than the impactor itself. This temporary cavity (often termed the transient crater; Dence et al. 1977) subsequently collapses under the influence of gravity to produce the final crater form. As the crater grows and collapses, large volumes of rock debris are ejected onto the surface of the Earth surrounding the crater. Close to the crater rim, this “ejecta deposit” forms a continuous blanket smothering the underlying terrain; further out, the ejecta lands as a scattered assortment of finegrained dust and larger bombs that may themselves form small secondary craters. ...

This user guide describes Google Earth Version 4 and later. Welcome to Google Earth! Once you download and install Google Earth, your computer ...