g20.    What is the theory of plate tectonics?

Alfred Wegner proposed the first theory of continental drift.  He thought that the continents floated on the ocean's crust like a ship goes through water. In the early 1960s, with the discovery of the mid-Atlantic Ridge, the theory of plate tectonics came into being. This caused great debate in the geologic community ­ much like religious conversions. The crust of the earth is divided into plates. Convection currents in the mantle move the plates. There are three types of plate boundaries. Divergent boundaries are present at the spreading centers or ridges. Convergent boundaries are at the trenches, and at some folds, faults and sites of mountain building. Transform boundaries are at sites such as the San Andreas Fault. (See Paleomap Project) Evidence for plate tectonics includes regular earthquakes and volcanoes from plate friction; continent shape - Africa and South America; matching fossils; and matching rock layers.

e08.    What are bioregions and biosphere reserves?

e10.    Why do organisms become extinct?

e15.    What was early life like?

m12.    Why are organisms becoming extinct?

m41.    How can matter affect the environment?

m52.    What causes air pollution?

m74.    How is soil important in the environment?

m78.    How do droughts and floods impact populations?

m79.    Where are our water supplies?