Volcanoes and Elapsed Time in Centuries!

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SWBAT determine how long ago volcanoes in the Four Corners area of the U.S. were active, using the Smithsonian's Volcano Database.

Big Idea

The advent of the internet has given us phenomenal access to real-world data that we can use to make practicing basic operations more relevant and interesting for our students.


10 minutes

The basic math skills underlying today’s lesson are addition and subtraction with regrouping, so prior to beginning today’s lesson, I have students work through four problems (one at a time) as a review.

  • Addition w/the standard algorithm (1567 + 2689
  • Addition w/expanded form (2368 + 8974)
  • Subtraction w/the standard algorithm (9012 - 8536)
  • Subtraction w/expanded form (8125 - 6443).


After the brief skill review above, I explain today's lesson.  I tell them that we we will be finding information in a database that lists the dates of volcanic eruptions!  We will accurately record the information on our study guide and then use an open number line to calculate just how long ago the volcano/volcanic area erupted/was active.

If needed, I teach the word database by looking at the words data and base.  Then I show the students the Global Volcanism Database because it's interesting and engaging.

Intro to Global Volcanism Database (for the teacher)

Guided Practice

40 minutes

We go through the 4 Corners Volcanoes Activity and have students in their answers on the Student Page. I do this as a whole group activity because that is what meets my students' skill review needs, but this activity can certainly be done with the 1st two problems as whole group practice and then the students complete the remainder on their own, viewing the PowerPoint on student computers.

Additionally, the writing is optional and based on the needs of your class.  I still have students who are making basic errors with conventions (no capital letter at the start of a sentence, no ending punctuation, random capitalization) and who have forgotten how to write number words!  If my students did not need the practice I would let them skip this part!

Mini Formative

7 minutes

I give students these two problems to solve independently, on a separate sheet of paper, so I can do a quick check before tomorrow's lesson to see how they are progressing.  When it's a basic skill, especially when it is something that most of them have done and previously mastered, a formative assessment doesn't need to be long or formal to provide the needed information.

1.  If a volcano last erupted in 325 BCE, how long ago was that?

2.  If a volcano last erupted in 11,780 BCE, how long ago was that?

I make students aware of the fact that attending to precision in this lesson means that they recognize that working with addition and subtraction with time (in years) is different than a "plain" addition or subtraction problem because the structure of time is arranged differently.

It helps to remind students when the underlying structure they are "looking for and making use of" varies from the simple base ten system.  (Another example is, of course, standard units of measure).


1 minutes

I tell students that tomorrow they will continue to work with database information related to the date of last volcanic activity, and that they will be looking up data on the Global Volcanism Page on their own or with a partner.