At a Glance: Plate Boundaries

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Where are earthquakes on Earth generally found? 

Produced by the Space Telescope Science Institute’s Office of Public Outreach in collaboration with the NASA Earth Observatory.

All images, illustrations, and videos courtesy of NASA except:
·       Alfred Wegener photo courtesy of Bildarchiv Foto Marburg
·       Drawings of continental drift by Alfred Wegener from The Movements of the Continents and the Oceans
·       Lystrosaurus illustration courtesy of Nobu Tamura
·       Sea creature illustration copyright The National Library of Israel, Shapell Family Digitization Project _and The Hebrew University of Jerusalem, Department of Geography – Historic Cities Research Project
·       Photo of Half Dome courtesy of D.L. Peck, U.S. Geological Survey
·       Photo of Kanchenjunga Mountain courtesy of Wikimedia user Anirban c8
·       Mountain formation illustrations by Marc Lussier (STScI)
·       Aerial photo of the Himalayan Mountains courtesy of Wikimedia user Pipimaru
Music courtesy of Associated Production Music
Written by Andrea Gianopoulos
Designed by Marc Lussier

Text, At A Glance, Tectonic Plate Boundaries. Various stars and galaxies hang in the sky around Earth.
A map unrolls onto a black background. Text, Using sound waves, or sonar, scientists have mapped mountains and trenches along the ocean floor.
The earth appears green and white while the water is brown. Bright orange lines intersect across the map. Text, Earthquake activity. Adding earthquake measurements to the map reveals a pattern. Earthquakes are concentrated along ocean trenches and mountain ranges.
A green, purple and red diagram is overlaid onto the map. text, Plate boundaries. These zones of earthquake activity represent the boundaries of Earth's tectonic plates.
A third diagram is overlaid onto the others, which colors in the tectonic plates with purples, red, blue, green, and orange. Text, At these boundaries, plates can interact in different ways.
Where two plates pull away from each other, they form a divergent boundary where new crust forms.
A white jagged line separates the Americas from Europe and Africa. Text, Mid-Atlantic Ridge. Along the Mid-Atlantic Ridge, the sea floor spreads at a rate of about one inch per year, or 15 miles every million years.
A plate west of South America labeled Nazca Plate. South American Plate is labeled beside it. Text, Convergent Boundary. The plates press toward a white line between them. Text, The area where two plates collide is called a convergent boundary. Arrows point toward the convergent boundary. Text, Convergent boundaries destroy crust as one plate dives under the other.
We zoom in. Text, Andes Mountains, Southern Peru. The Nazca Plate's denser oceanic crust dives below the lighter continental crust of the South American Plate, which crumples and folds to form the Andes Mountains.
We zoom back out to the tectonic plate diagram. Text, San Andreas Fault. Transform Boundary. A boundary where two plates slide horizontally past each other and no crust is destroyed or created is called a transform boundary. Arrows point in opposite directions up and down the length of the white Transform Boundary line.
We zoom in. Text, San Andreas Fault, California, U S A. White dots line the San Andreas Fault. The Mojave Desert is to the east of it and the San Gabriel Mountains are southwest, with Los Angeles even further south and to the west. Text, The 800-mile-long San Andreas Fault in California is a transform boundary.