SWBAT use information from a database and addition and subtraction strategies to determine the elapsed time since the last volcanic activity for a given volcanic location.

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 students.

8 minutes

I teach this as an end of the 3rd quarter lesson. My purpose is to review the regrouping strategies for addition and subtraction that sometimes temporarily drop out of the students' working memory.

This is a very teacher-directed, concise, targeted review of the different methods taught in earlier lessons this year. (Link through when those lesson are finalized). I go over a specific, pre-planned set of problems each day to address different levels of difficulty and common errors. Here is the set for today! (insert doc).

Here is a video I use to give the students a different way of viewing the same information, instead of just hearing me talk through the same procedure again. This short cartoon clip reviews addition with expanded notation.

40 minutes

On this second day in the addition/subtraction review volcanoes series, I show students again how to navigate to the Smithsonian’s *Global Volcanism* page. We do the first several problems together, and then I release them to work on their own with a partner.

I invite students who prefer to stay at the carpet with me to continue to work in a more guided practice setting. Another option is to help the students set up the number lines, especially for the problems in which the last eruption was AD (these require slightly more complicated math), and then release them to independent work.

If your students are unable to use computers for this activity, I’ve also created a Volcanoes of California powerpoint that shows the information about each volcano exactly as it appears on the website. This can be used to complete the activity as well.

Either way, I suggest having students use the Volcanoes of California Student Activity Pages to keep themselves on track. This makes it easier for you to observe their work as you walk around the room and confer with students, and also it makes it harder for students to accidentally skip some volcanoes. You know what they say about people who skip over volcanoes…

Here is a teacher key so you don't have to look up all the volcanoes yourself (though I know you want to, because volcanoes are cool!) in order to check their work!

5 minutes

To conclude this lesson, students answer one of the following questions orally or in their math journal (or even just written on their white board):

How would you explain how to calculate elapsed time in years using a number line?

What is B.C. / B.C.E.? Why is the numbering reversed? (300 B.C.E. is longer ago than 50 B.C.E.)

What is something you understand about elapsed time in years on a number line that you didn't understand before?

Which part of this lesson helped you practice addition with regrouping?

Is there a part of this lesson that you didn't like or found confusing? Why? How would you change it?