SciShow Kids recently published a new video that explains to children how glaciers are formed and how they change over time. SciShow Kids is intended for early elementary school grades and this video about glaciers not an exception to that pattern.
For older students you might want to take a look at
How Do Glaciers Move? which explains how glaciers are formed, the physical properties of glaciers, and how glaciers move. The video also answers the question of whether a glacier is a solid or a liquid.
Finally, the Extreme Ice Survey offers a Google Earth file (clicking the link will launch a KML download) that displays the results of the Extreme Ice Survey. In this Google Earth file users can view glaciers, historical data about glaciers, and some video clips about shrinking glaciers. The Extreme Ice Survey website has high quality photos and time lapse videos from the surveyors.
Use one of these seven tools to create a science lesson with either video that is posted above.