1. Glaciers

2. Glaciers are massive streams of ice flowing down across the landscape. Gravity pulls them downward and their weight causes them to move, ever so slowly, over mountains cutting into the rock and soil of the land.

3. Glaciers

4. Glaciers are massive agents of erosion and, when they melt away, can leave uniquely indentifiable landscape features, such as the U- shaped valley of Yosemite in California.

6. Glaciers Climate changes (repeating cycles from warm to cold) allow glaciers to grow and advance, or to melt back (retreat). Over the past 4 to 5 million years there have been many ice ages, with several of them being major episodes lasting tens of thousands of years when continental glaciers covered large portions of North America and Europe.

7. Glaciers During the last ice age, the biomes of the continents were drastically different from what they are today.

9. Glaciers Much of Greenland and Antarctica are still under ice- age conditions today.

10. Glaciers We currently live during an ‘interglacial period.’ Prior to about 10,000 years ago, large ice sheets, similar to modern examples on Greenland and Antarctica, covered large portions of North America and Europe.

11. Glaciers With so much water trapped in continental glaciers, sea level was much lower. Sea level has been steadily rising as the ice sheets melt away. At the peak of the last ice age, sea level was as much as 350 to 400 feet lower than today, and areas that are now continental shelves offshore were exposed as coastal plains.

12. Many mountain ranges, including California’s Sierra Nevada were covered with alpine glaciers.