There has been considerable speculation in recent years that the build-up of carbon dioxide and methane in the atmosphere, caused by man's utilization of fossil fuels since the industrial revolution, will lead to global warming caused by an enhanced "greenhouse effect". Such warming could potentially have a dramatic economic impact on the United States by shifting agricultural belts farther north than they are today. Melting of polar ice caps would cause the oceans to rise resulting in the eventual inundation of coastal areas, thus flooding many of our major cities. Although predictions about the effects of future global warming are speculative and open to much debate, geologists recognize that there were many episodes of global warming in Earth's history. Better understanding of ancient environments may help us be better able to predict the future.
Evidence suggests that the Cretaceous period was notably warmer than today, with no polar glaciation. Global sea-level was high, and broad shallow seas inundated many continental regions worldwide. In North America, the Western Interior seaway brought warm moist air and equable temperatures into what is today the Rocky Mountain and Great Plains region. Climatic and vegetational belts typical of today's Gulf Coast existed much farther north, and thick peats accumulated in coastal wetlands with a subtropical flora of tree ferns, cycads and sequoia. Detailed studies of the coals that formed by deep burial of these peats indicate that at least some of the peats formed in a wetland type characteristic of areas with year round precipitation.
For More Information:
Laura Roberts, Mark Kirschbaum, or Pete McCabe
U.S. Geological Survey
Denver Federal Center
Denver, CO 80225-0046
For a copy of this poster, please send a written request to:
USGS Energy Resources Program
915 National Center
Reston, VA 20192