Tectonics and
Landforms
Along the boundary of the Earth's tectonic plates a fiery drama of
catastrophic proportions is played out. Movement of the Earth's crust creates
earthquake activity and in some places great outpourings of lava
extrude onto the surface.
Figure 15.16 Earth's Lithospheric plates
(Courtesy: NASA Goddard Space Flight Center)
Four types of plate boundaries are recognized and are depicted
in Figure 15.17.A spreading
or divergent boundary occurs where plates are moving away
(diverging) from one
another, like that occuring along the midocean ridge where new crust is formed
 .
Convergent
boundaries are located where subduction is active and the lithosphere is being
"consumed". This occurs where two plates collide with one
another. Transform
boundaries occur where plates are grinding past one another, like
the San Andreas fault. Plate boundary zones
are broad belts in which boundaries are not well defined
and the effects of plate interaction are unclear.
Understanding plate motions (USGS) is important in deciphering
land forming processes that occur along plate boundaries.
Figure 15.17 Tectonic Settings
(Courtesy of USGS)
Figure 15.18 Plate tectonics: Geological features of divergent plate boundaries
Figure 15.19 Plate tectonics: Geological features of convergent plate boundaries
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