"The expansions and contractions of those environments have pretty profound effects on life on Earth," said Shanan Peters, a University of Wisconsin-Madison assistant professor of geology and geophysics and leader of the study.
Peters measured two main types of marine shelf environments preserved in the rock record, one where sediments are derived from land erosion and the other composed primarily of calcium carbonate, which is produced in-place by shelled organisms and by chemical processes. The differences between the two areas in sediment stability, temperature and the availability of nutrients and sunlight have important biological consequences, according to Peters.
Arnold I. Miller, a paleobiologist and professor of geology at the University of Cincinnati, says the new study is striking because it establishes a clear relationship between the tempo of mass extinction events and changes in sea level and sediment. "Over the years, researchers have become fairly dismissive of the idea that marine mass extinctions like the great extinction of the Late Permian might be linked to sea-level declines, even though these declines are known to have occurred many times throughout the history of life. The clear relationship this study documents will motivate many to rethink their previous views."
Over the course of hundreds of millions of years, the world's oceans have expanded and contracted in response to the Earth's shifting tectonic plates and climate changes. During some periods, vast areas of the continents were flooded by shallow seas such as the shark- and mosasaur-infested seaway that neatly split North America during the age of the dinosaurs.
As those flooded areas drained back into the sea, animals that swam in them went extinct; conditions on the marine shelves that once supported a vast diversity of life also changed.
That's not to say volcanic eruptions, killer asteroids, or disease and competition among species could not have played a role, Peters said. But the new study provides a common link to mass extinction events over a significant stretch of Earth's history and suggests that few of them were controlled by just one environmental influence.”
Between volcanism, earthquakes, tsunamis, climate changes, and the expansion and contraction of the seas, this fragile earth, our island home, is constantly changing. This study is important because it shows the effects of sea levels on plant and animals species, many of which became extinct because of the changing sea levels. It is important also as further evidence of the changing environment of ancient civilizations.
About 150,000 years ago there was a major uplift of the Angolan ridge in the area of the equator. The upper Nile receives its chief supply of water from this mountainous region. From there streams pour eastward into Lake Victoria, Africa's largest lake (over 26,000 square miles), and to the west and north into Lake Edward and Lake Albert. The waters of the Nile flow northward, but around 12,000 years ago all of the region between Lake Chad and the Nile was very wet. This is the time of Noah's flood.
The story of Noah’s flood speaks of the effects of tectonic and climate change over a vast area from central Africa to the Indus River Valley. Noah lived during a period of wetness in Africa in the area called Bor-Nu (Land of Noah) near Lake Chad. This period(the late Halocene) was followed by declining water levels. Since Noah and other Afro-Asiatic kingdom builders controlled the major water systems, this decline signaled the end of their control. The gradual breakdown of the socio-political fabric of the Afro-Asiatic Dominion, whose chiefs controlled the waterways, is likely due to these changes.For more on Noah's flood, read this.
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