News Flash: Ice-out at Thoreau's Walden Pond

"The ice at Walden is OUT!" proclaimed Michelle Dumas of Walden State Park Reserve. "The official date and time is Monday March 1st at 8am."

Congratulations to Ms. Plenz's students for predicting the future! "The
seventh graders in my class came to the consensus that March 1st would be the date for ice out on Walden Pond." (plenz@nconnect.net)

But how did they know this? Compare Thoreau's ice-out records from the 1800's to those for the late 1900's, collected by Journey North students (see below) and tell us what you think:

Challenge Question #5
"According to Thoreau's records, what was the average ice-out date during his time? What is the average date during our time, according to records kept by Journey North students? How might you explain the change?"
 Fayerweather School Students Visiting Thoreau's Cabin Photo: Susan Wheelright

Ice-Out Records for Walden Pond
These are the dates the ice went out at Walden Pond as collected in the 1800's by Henry David Thoreau:

• 1845 April 1
• 1846 March 25
• 1847 April 8
• 1851 March 28
• 1853 March 23
• 1854 April 7

..... and collected in the 1900's by Journey North students

• 1995 March 18
• 1996 March 23
• 1997 February 22
• 1998 February 26
• 1999 March 1

Introducing the Next Official Ice-Out Observation Post
 Official Ice-Out Observation Posts Spring, 1999
Next in line to thaw should be Lake Minnetonka. This still-frozen lake is located right outside the window of the Journey North headquarters in Minnesota. People here have always been eager for spring, and for the past 112 years they've kept ice-out records for this lake.

By law, all ice-fishing houses must be off the ice by March 1st, because cars & trucks must DRIVE on the ice for the task.

Ice-out dates are one of the best natural ways to measure the amount of heat the earth has received, and compare spring's pace from year to year. See if you can answer this question after looking at:

Challenge Question #6
"When do you predict ice-out of Lake Minnetonka will occur in Spring, 1999?

How to Respond to Today's Challenge Question

1.Address an e-mail message to: jn-challenge-spring@learner.org
2. In the Subject Line of your message write: Challenge Question #5 (or #6)
3. In the body of EACH message, answer ONE of today's questions.

Copyright 1999 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form