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media type="custom" key="2672601"  = =  **__ Divergent boundaries __**  ·  Places where plates are coming apart are called divergent boundaries.  ·  As the plates separate along the boundary, the block between the faults cracks and drops down into the soft, plastic interior (the asthenosphere).
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 ·  The sinking of the block forms a central valley called a rift.  ·  __Magma__ (liquid rock) seeps upward to fill the cracks. which a new crust is formed along the boundary.  ·   Also  earthquakes occur along the faults, and volcanoes form where the magma reaches the surface.  ·  divergent boundary crosses the land, the rift valleys which form are typically 30 to 50 kilometers wide.  ·   Some examples:  <span style="FONT-FAMILY: 'Arial','sans-serif'"> <span style="FONT-SIZE: 18pt; LINE-HEIGHT: 115%; FONT-FAMILY: 'Arial','sans-serif'"> Include the East Africa rift in Kenya and Ethiopia, and the Rio Grande rift in New Mexico <span style="FONT-SIZE: 18pt; LINE-HEIGHT: 115%; FONT-FAMILY: Symbol; mso-fareast-font-family: Symbol; mso-bidi-font-family: Symbol"> ·  <span style="FONT-SIZE: 18pt; LINE-HEIGHT: 115%; FONT-FAMILY: 'Arial','sans-serif'">Where a divergent boundary crosses the ocean floor, the rift valley is much narrower, only a kilometer or less across, and it runs along the top of a midoceanic ridge. <span style="FONT-SIZE: 18pt; LINE-HEIGHT: 115%; FONT-FAMILY: Symbol; mso-fareast-font-family: Symbol; mso-bidi-font-family: Symbol"> ·  <span style="FONT-SIZE: 18pt; LINE-HEIGHT: 115%; FONT-FAMILY: 'Arial','sans-serif'">Oceanic ridges rise a kilometer or so above the ocean floor and form a global network tens of thousands of miles long. <span style="FONT-SIZE: 18pt; LINE-HEIGHT: 115%; FONT-FAMILY: Symbol; mso-fareast-font-family: Symbol; mso-bidi-font-family: Symbol"> ·   Some examples:  <span style="FONT-FAMILY: 'Arial','sans-serif'"> <span style="FONT-SIZE: 18pt; LINE-HEIGHT: 115%; FONT-FAMILY: 'Arial','sans-serif'">the Mid-Atlantic ridge and the East Pacific Rise. <span style="FONT-SIZE: 18pt; FONT-FAMILY: Symbol; mso-fareast-font-family: Symbol; mso-bidi-font-family: Symbol"> ·  <span style="FONT-SIZE: 18pt; FONT-FAMILY: 'Arial','sans-serif'">Plate separation is a slow process. For example, divergence along the Mid Atlantic ridge causes the Atlantic Ocean to widen at only about 2 centimeters per year. ||