All of you have seen pictures of how the land masses were arranged at various times in the geologic past. You may even have heard that the region where El Paso now resides was once near the equator. You've probably wondered how scientists can trace the past movements of continents. How? Look to the magnetic field of the earth. Everyone knows that a compass needle points north. Not as evident is the fact that the needle also changes its up and down angle depending on how close it is to the magnetic poles. Even less commonly known is that many of the particles that make up sedimentary rocks are magnetized, and tend to align themselves to the magnetic field as they settle down to begin the process of becoming rock.
By mapping the magnetic orientation of such rocks and plotting them by
their age, the ancient positions of the rocks, and thus the continents on which they
ride, can be determined. Not as exact as present day surveying, but a dependable
glimpse of the past.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.