I Wonder Why

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Across
  1. 4. the usual weather conditions in place
  2. 7. ground that is frozen all year
  3. 8. to strike or bump into one another
  4. 10. the gases surrounding the Earth
  5. 11. a structure that is put up quickly for protection
  6. 12. letting only some light pass through
Down
  1. 1. an Inuit hose, shaped like a dome and made of blocks of ice
  2. 2. tiny amount or small piece
  3. 3. to make dirty or harmful to health
  4. 5. one of the huge plains in the arctic region; treeless
  5. 6. huge blocks of freshwater ice that break off from glaciers
  6. 9. an instrument for showing directions