Student Activities

Predict Old Faithful

Grade Level:
Upper Elementary: Third Grade through Fifth Grade

Though most geysers are not predictable, Old Faithful is famous for its regularity. Use the rangers' formula below to predict its next eruption. You will need a place to record your work and answers.

Step 1

Open the Old Faithful Geyser Live-stream Webcam. Wait for Old Faithful to erupt and time its eruption from when water begins splashing continuously out of the cone until only steam is coming out.

A. Start Time: _______
B. End Time: _______
C. Length of Eruption (to nearest 1/2-minute): _______

Step 2

Using the table below, find the length of the eruption (C) in the first column. Read directly across to the second column in the same row and note the interval or number of minutes (D) until the next eruption.

Table of Old Faithful eruption lengths and intervals between eruptions.
C. Length of Eruption D. Interval Until Next Eruption
< 3 minutes 68 minutes
> 3 minutes 94 minutes

Step 3

Add the start time for the first eruption (A) with the interval number of minutes until the next eruption (D). This is the prediction for the next eruption!

_________(A) + _________(D) = ____________ (Your Prediction!)

Step 4

Return to the Old Faithful Geyser Live-stream Webcam to find the rangers’ prediction for the next eruption: __________ How close is your prediction to theirs? ________________________

Step 5

Watch the next Old Faithful Geyser eruption. When did it start? ________ How did the actual start time compare to your prediction? To the rangers’ prediction? Remember, Old Faithful is a natural feature and changes often, so any prediction may not prove to be exactly right.


Worksheet for predicting the next eruption of Old Faithful Geyser.

Download Predict Old Faithful

Last updated: August 16, 2018