The Great Ice Age: what caused it?

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Across
  1. 2. frozen ground water that freezes solid all year long.
  2. 5. warms the ocean and releases vapor and smoke (aerosols).
Down
  1. 1. covered the whole earth and led to wetter winters and cooler summers.
  2. 3. formed from the sea itself.
  3. 4. Huge sheets of ice that form from snow on land.