Paws Along the Trail with a River Ice Break-up

Teams resting on the frozen Fish River with the village of White Mountain nestled on the hills

Rivers flow, yet freeze throughout Alaskan winters.  Airplanes use the solid rivers as runways.  Snow machines criss cross the wide, frozen expanses.  The Iditarod mushers spend plenty of time sledding and camping on rivers as they follow the trail toward Nome.  

Teams rest on the Fish River near the checkpoint of White Mountain

A village on the northern route of the Iditarod, Nenana, has a yearly tradition of predicting when the Tanana River ice will break up in the spring.  They have been guessing the date and time since 1917!  A question for younger students might be, how many years has this contest been done?

Map of the tripod placement

A tripod is built and put into the thick ice along with a line tied to a clock in town.  The clock will stop when the melting ice moves the tripod 100 feet and the line breaks.  The ice on the river averages 42 inches thick, so melting takes awhile with water eroding the ice underneath and the sun melting it from the surface.

Tickets are sold throughout Alaska for $2.50 per guess.  Organizers of the event provide the break-up dates and times through the years so you can statistically analyze when the ice movement will make the clock stop.  An AP Stats teacher and I have attached a  lesson plan for an Intro to Statistics or AP Statistics activity using information from the Nenana Ice Classic.  

Nenana Ice Classic and Stats

Years and Dates Data

Knowing if and when the ice will break up is pretty important to Alaskans and mushers.  A dog team wants steer clear of any rivers during spring break-up!