Racer

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Across
  1. 4. one of the three rocks
  2. 5. one of the three rocks
  3. 7. plates slide past one another
  4. 8. one of the three rocks
Down
  1. 1. goes away from each other
  2. 2. we walk on it
  3. 3. tiny pieces of rock
  4. 6. it is the biggest layer