Sea Floor Spreading

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Across
  1. 3. the crust composed of granite
  2. 6. allows part of the ocean floor to sink back into the mantle
  3. 7. the boundary that moves apart
Down
  1. 1. the boundary that moves together
  2. 2. created by 2 convergent boundaries
  3. 4. composed of basalt; more dense
  4. 5. ridge mapped by a sonar