but just as alarming to scientists here in alaska is what s happe b ground the warming earth is literally changing what s beneath our feet. for most of alaska that would be permafrost, a frozen layer of earth made up of soil and gravel the permafrost is thawing raising concerns the releas of carbon dioxide and methane could lead to even more warming just outside fairbanks i venture into a place where time is literally frozen the army corps of engineers permafrost tunnels where 40,000 years of earth s history are studied, ice, ancient grass and woolly mammoth bones is that a bone there good eye. that s a mammoth bone. reporter: the tunnels originally built in the 60s to study underground construction need to feel how cold it is. yeah, that s it feels cold. that s solid ice. reporter: now that thawing permafrost is heating roads and sinking