 <![CDATA[<a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=gif::::/sites/dl/free/0078664187/179001/ch07_chapter.gif','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (0.0K)</a>]]> |
Extinction of the Dinosaurs
Hypotheses abound concerning the environmental upheaval that caused the final Cretaceous extinction 65 million years ago. In 1980, Nobel prize winner Luis Alvarez and his colleagues
published a paper in Science magazine that proposed the extinction of the dinosaurs and many other creatures was due to the impact of an asteroid or comet with Earth. The element
iridium was used as evidence to support this proposal. |  <![CDATA[<a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/0078664187/179001/ch7_1.jpg','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (25.0K)</a>]]> |
Iridium, the most corrosion-resistant metal known, is rarely found in Earth’s crust. But, it is abundant in Earth’s core and in meteorites and asteroids. Large
amounts of iridium have been found in a clay layer that marks the end of Cretaceous-period rock and the beginning of Tertiary rock (the K-T boundary). Researchers have found up to 100
times the amount of iridium in this clay layer than is normally found in the soils around the world. |
The Alvarez hypothesis of the final K-T extinction proposes that a 10- to 20-km diameter asteroid collided with Earth and released large quantities of vaporized material (including
iridium) into the atmosphere. This material was distributed globally and blocked out the Sun for months causing "impact winter". Chemical reactions between substances in the
atmosphere and these pollutants caused the formation of acid rain. A crater estimated to be 160 to 240 km wide was discovered off the tip of the Yucatan Peninsula in the Gulf of Mexico. Much of the Chicxulub crater lies under the ocean and is hidden
under 65 million years of sediment. Research is on-going as is the debate over whether the asteroid that formed this crater could have caused mass extinction.
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 <![CDATA[<a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=gif::::/sites/dl/free/0078664187/179001/POWproblem_1.gif','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (0.0K)</a>]]> | Locate iridium on the periodic table and identify the group of elements it belongs to. |
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 <![CDATA[<a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=gif::::/sites/dl/free/0078664187/179001/POWproblem_2.gif','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (0.0K)</a>]]> | What is the electron configuration of the element iridium? |
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 <![CDATA[<a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=gif::::/sites/dl/free/0078664187/179001/POWproblem_3.gif','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (0.0K)</a>]]> | Would iridium be magnetic? Explain your answer. |
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 <![CDATA[<a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=gif::::/sites/dl/free/0078664187/179001/POWproblem_4.gif','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (0.0K)</a>]]> | What properties of iridium make it a good source of evidence for the impact theory? |
 <![CDATA[<a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=gif::::/sites/dl/free/0078664187/179001/webLinks.gif','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (1.0K)</a>]]> | Useful Web Sites:
Periodic Spiral
Comets and Meteorites
Mass
Extinction & Rise of Dinosaurs Tied to Cosmic Collision
National Museum of Natural History
Iridium "Layer"
Iridium |
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