| A | B |
|---|
| Ice Age | Period during which low temperatures caused large areas of Earth's water to freeze |
| migrate | To move from one area to another |
| artifact | Object made by people in the past |
| glacier | Thick sheets of ice that covered Earth's surface during the Ice Age |
| theory | One possible explanation for something. |
| archeologist | Scientist who studies the artifacts of people who lived long ago and draws conclusions from them. |
| ceremony | Activity done for a special purpose |
| mesa | High, flat landform that rises steeply from the land around it |
| drought | Long period without rain |
| civilization | Culture with organized systems of government, religion and learning |
| surplus | More than is needed |
| specialize | Focus on one particular product, activity, or job. |
| pyramid | Building with three ore more sides shaped like triangles that slant toward a point at the top. |
| empire | Large groups of lands and peoples ruled by one leader |
| tribute | Payment a ruler demands from people he or she rules. |
| slavery | Practice of owning people and forcing them to work. |
