Solid Earth Geophysics Ali Oncel [email_address] Department of Earth Sciences KFUPM Today’s class: Plate Motions Reading: Fowler Chapters 2-3 http://neic.usgs.gov/neis/plate_tectonics/plates.html
OVERVIEW: PLATE TECTONICS Basic concept: The outermost layer ( LITHOSPHERE ) is divided in a small number of “rigid” plates in relative motion one respect to the other. It FLOATS on the weak ASTHONOSPHERE .
As a result of DISCOVERY, the plates are made up of both oceanic and continental material, whereas the ONLY oceanic parts of plate are created or destroyed. However, it is hard to understand why continental material usually is not destroyed at convergent plate boundaries.
Sea floor spreading at the mid ocean ridges produces only oceanic lithosphere.
From: Fowler, the solid Earth
How many plates? What is the largest plate and smallest plate?
Ocean or continent?
Oceanic crust is primarily basalt
Continental crust is primarily granite
What are the differences between these 2 rock types?
What are the criteria for deciding whether Earth’s crust any location is oceanic or continental in origin?
Why does the Pacific plate subduct?
As new crust cools, it thickens and becomes denser.
Blue (cool) colors on this map show older crust, warm colors show younger crust .
Crustal Density : 2.8X10 3 kgm -3
Mantle Density : 3.3 X10 3 kgm -3
PARALLEL VALLEYS; VOLCANOES AND EARTHQUAKES.
Oceanic- Continental Plate Separation VOLCANOES AND EARTHQUAKES CONCENTRATE Divergent Boundaries
DEEP-SEA TRENCH; VOLCANIC ISLAND ARC .
Convergent Boundaries Ocean-Ocean Convergence Ocean-Continent Convergence A VOLCANIC BELT OF MOUNTAINS FORMS