NOAA	Science News Reader Supplement HERE & NOW Plate Tectonics Vicki M. Harder

The theory of plate tectonics is the paradigm of the geological sciences. It explains the occurrence of earthquakes and volcanoes, the distribution of rock types, the widespread occurrence of organisms, etc., on Earth. The study of plate tectonics that deals with the processes by which the lithosphere (plate) is moved (tectonics) laterally over the asthenosphere. The field of plate tectonics has a long history of development beginning with the concepts of continental drift, sea-floor spreading, and polar wandering.

USGS

Much is still left to study. How does life exist along the midoecean spreading centers? Why is the Tibetean plateau so flat? When, and how quickly did the continents form and where have they traveled through time? Basically, plate tectonics involves the study of plate motions and plate margins. In the study of plate motion through time the question that must be answered is when did the first continental crust form and how has it evolved over time? The Science News reader article Continents grew early in Earth's history adresses the problem of the development of continental crust by looking at 2.7 billion-year-old basaltic rocks. The conclusion they reached is not fully agreed upon by all but is still considered an advance in the study of early Earth history. Another plate motion study reported in the Science News reader article The original Arkansas traveler illustrates how a portion of the continent can be pried loose and end up plastered to a completely different continent.

Topography along the midoceanic ridge (red is high, blue is low)

The motions of plates are interrelated with plate margins. At the margins the plates are either moving away from each other (divergent plate margin) or moving toward one another (convergent plate margin). Sea floor vent

In the Science News reader article The Light at the Bottom of the Ocean: Oceanographers struggle to explain a strange glow from seafloor vents, scientists are studying a divergent plate margin, the midoceanic ridge. At these localities they are looking for an explanation of how life can survive under severe conditions and whether it means that all life on Earth arose from around these midoceanic spreading centers.

Alvin

A continent-continent convergent plate margin between India and the Eurasian continent is being studied to determine what actually happens at this collisional boundary as explained in the Science News reader article Tibet Reveals Its Squishy Underbelly. As in all collisional plate boundaries, the continental crust is too bouyant to be subducted, or recycled back into the mantle. In the case of Tibet, a large mountain range, the Himalayas, formed. However, scientists have suspected for some time that some continetal crust has been recycled into the mantle through the subduction processes. The Science News reader article Recycled crust hails a glittering taxi offers the first evidence that this process actually occurs.

Plate Tectonics and People Vents Video Clips