Geologists suspect Alaska contains only a small triangle of original North America, along its east-central boundary with Canada.

Fossils suggest the rest of Alaska was formed from a patchwork of small land chunks, known as terranes, that collected against North America like flotsam between 251 million and 60 million years ago.

Snail and sponge fossils--found in the Alexander terrane encompassing Alaskas southeast panhandle and in the Farewell terrane--provide key links to Eurasia.