Geologic Time Puzzle

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Across
  1. 3. Complex multicellular organisms first appeared; a vast supercontinent known as Pangea formed and subsequently split up into the continents that we know today; plants and animals emerged from the sea and began to live on land; the dinosaurs came and went; Earth was shaken by three mass extinction events; and an intelligent primate species began to explore the universe.
  2. 4. Continents formed and our modern atmosphere developed, while early life evolved and flourished.
  3. 6. North America's characteristic landscapes began to develop during the Cenozoic.
  4. 7. Methane droplets in the air shrouded the young Earth in a global haze.
Down
  1. 1. Modern plate tectonics became active, and the ancient cores of the continents moved over wide areas of the globe, accumulating smaller fragments of crust and sometimes colliding with other large landmasses.
  2. 2. Pangaea began separating into the modern continents, and the modern Rocky Mountains rose.
  3. 4. Fish diversified and marine organisms were very abundant.
  4. 5. The solar system was forming within a cloud of dust and gas known as the solar nebula, which eventually spawned asteroids, comets, moons and planets.