Science4Fun
Science4 Fun: Ice Ages
What is an Ice Age? Discusses the five major ice ages and the causes.
CK-12 Foundation
Ck 12: Earth Science: Tree Rings, Ice Cores, and Varves Study Guide
[Free Registration/Login may be required to access all resource tools.] This study guide summarizes key points about tree rings, ice cores, and varves. Includes a question to check for understanding.