Essay Questions
 
 1.  How does continental-continental convergence form mountains?
 
 A continental-continental convergence generally does not involve any subduction of the continental plate. Instead, the two plates collide causing the two masses to squeeze, fold, thrust and deform. The end result is a new mountain range.
 
 
 2.  Why is seafloor geology simpler then continental geology?
 
 The geologic and topographic structures of the ocean floor primarily reflect plate tectonic activity that has occurred over the past 150 million years of the 4.5 billion year age of the Earth. Seafloor geology is far simpler than the geology of the continents because erosion rates are lower and also because the continents have suffered multiple collisions associated the opening and closing of ocean basins (Wilson Cycle).
 
 
 3.  What variables must be know in order to determine the position of a moving submarine?
 
 Consider measuring accelerations in a moving submarine or aircraft in order to determine your position as a function of time. (Of course your starting position and velocity must also be known.) If the windows of your vehicle are closed, a true acceleration cannot be distinguished from a variation in the pull of gravity. Thus the gravity data are needed for correction of inertial navigation/guidance systems.
 
 
 4.  Why is the triple junction a good example of seafloor spreading?
 
 The Indian Ocean Triple junction (27 deg S latitude, 70 deg E longitude) is a textbook
 example of seafloor spreading. Spreading ridges are characterized by an orthogonal pattern of ridges and transform faults. The scar produced in the active transform valley is carried by seafloor spreading out onto older seafloor leaving evidence of the past plate motions. At this Indian Ocean site, three spreading ridges intersect forming a triple junction as described by plate tectonic theory. The theory predicts that the ridges would intersect at 120û angles if the three ridges were spreading at exactly the same rate
 
 
5. Why do most volcanoes appear as chains of mountains?  What would explain volcanoes that are not part of a chain?  How can gravity maps and satellite data be used to explore these problems?

Students will have  to use additional sources to answer this question.

Many volcanoes appear in chains, perhaps associated with mantle plumes, there are many more that do not fit this simple model. Moreover, numerous undersea volcanoes are long linear ridges with aspect ratios of 20 or more. These features suggest that the plates are not exactly ridged as predicted by the simple plate tectonic theory. Using these data we are exploring the internal deformations of the plates, especially outboard of trenches where the forces generated by the slab-pull force of the subducted plates is greatest.