Science of Ice Ages

2. a warm period during an ice age when glaciers shrink
4. what covered the continents during ice ages
7. large pieces of ice that often start in the mountains
9. could start an ice age by putting a lot of ash and particles into the air
12. the last glacial period, about 18,000 years ago
13. The Earth moving around the sun
14. 2.4 billion years ago when Earth was completely covered in ice
16. how the atmosphere behaves over a long period of time
18. describes the shape of Earth's orbit and how close the Earth gets to the sun

1. a gas that is in the atmosphere
3. the number of ice ages over Earth's history
5. caused by the Earth being tilted towards the sun
6. how many millions of years ago the most recent Ice Age started
8. a cold period during an ice age when glaciers grow
10. move heat from the equator to the poles, and cold water from the poles to the equator
11. the conditions of the atmosphere over a short period of time
15. the name of the effect that traps heat near Earth's surface
17. millions to tens of millions of years when the temperature of the Earth is cold