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In 1988, zebra mussels were inadvertently introduced to Lake St. Clair, and quickly spread throughout the Great Lakes and into many inland lakes, rivers, and canals.

The spiny water flea (Cercopagis pengoi) was the most recent species to enter the Great Lakes. Type text or a website address or translate a document. This body, a native of Middle Eastern seas, is a small crustacean predator that can reproduce both sexually and, more commonly, parthenogenically (without fertilization). (Jude, 2001)

More than 145 different plants and animals have invaded the Great Lakes in the past 200 years. Some of these, such as the sea lamprey and the zebra mussel, have had economic as well as ecological impacts. The Great Lakes have been especially hard hit by the invasion of invasive species due to the presence of numerous canals and international ship traffic. Ballast water transfers from such ships have introduced invasive species such as zebra and quagga mussels, spiny waterfleas, Eurasian ruffe and the round goby.

Not all non-native species are invasive and harmful. But many can completely take over and entirely change whole established ecosystems. Invasive species may be as harmless looking as green plants or a frog. Exotic ornamental plants, flowers and trees, or animals that are brought into an ecosystem can increase species diversity at local level, but then, introduced species can take, displace or kill native indigenous species, and in some cases , cause the extinction of plant and animal species (Jude, 2001)

Asian carp have been found in the Illinois River, which connects the Mississippi River to Lake Michigan. (Pultz, 2005)

To prevent and control additional invasions in the Great Lakes, coordinated efforts are under way by U.S. and Canadian governments, eight state governments, two provincial governments, and regional and local programs.


The theory of plate tectonics has its beginnings in 1915 when Alfred Wegener proposed his theory of "continental drift". Wegener proposed that continents broke through the crust of the ocean basins, which would explain why the outlines of many coastlines (such as Africa and South America) seem to fit like a puzzle. (Zhao, 2004)

Theory of plate tectonics is important for Earth's history as the progress of the earth sciences and the advancement of technologies associated with the understanding of our planet during the 1940's and 50's have led geologists to develop a new way of looking at the world and how it works.

Plate tectonic theory asserts that Earth is divided into core, mantle, and crust. The crust is subdivided into oceanic and continental crust. The oceanic crust is thin (3-4.3 mi [5-7 km]), basaltic (<50% SiO2), dense, and young (<250 million years old). In contrast, the continental crust is thick (18.6-40 mi [30-65 km]), granitic (<60% SiO2), light, and old (250-3,700 million years old). (Zhao, 2004)

Boundaries are adjacent areas where plates meet. Divergent boundaries are areas under tension where plates are pushed apart by magma upwelling from the mantle. Type text or a website address or translate a ...
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