Plate Tectonics 8.9A,B

Scientists recently discovered that rocks collected from the Franklin Mountains in West Texas and rocks collected from mountains in eastern Antarctica were exactly the same age. Further research showed that the rocks were chemically and geologically the same and came from the same magma source. This discovery provides evidence of —

• coastal erosion.
  
• plate tectonics.
  
• ocean currents.
• glacial melting.
  

Rift valleys can form when fractures in Earth’s crust widen. The valley walls slowly move at a rate of only a few millimeters a year. Which of these best describes the type of tectonic activity that forms rift valleys?

• Rift valleys form where a continental plate moves under an oceanic plate.
  
• Rift valleys form where a plate slides horizontally past another plate.
  
• Rift valleys form where two plates move away from each other.
  
• Rift valleys form where an oceanic plate moves under another oceanic plate.
  

The map shows some of Earth’s plate tectonic boundaries. Based on the map, volcanic activity would most likely be found at —  

• Location W
• Location X
• Location Y
• Location Z

A mid-ocean ridge separates the Pacific plate and the Nazca plate off the western coast of South America. Which statement best describes the relative motions of the Pacific and Nazca plates?

• The Pacific and Nazca plates are both moving to the east.
  
• The Pacific and Nazca plates are both moving to the west.
  
• The Pacific plate is moving to the west, and the Nazca plate is moving to the east.
  
• The Pacific plate is moving to the east, and the Nazca plate is moving to the west.

The model below shows two continental plates. The folded mountains in this model form at which type of plate boundary?

• Transform boundary
  
• Divergent boundary
• Subduction boundary
• Convergent boundary