Let's see how seriation can help us solve a mystery.

Imagine that you have information that a treasure is buried in an old junkyard in your town. You don't know which junkyard, but you know that it's the oldest junkyard in town. How could you figure out which junkyard is the oldest?

You can use seriation!

In these junkyards, you can find lots of things that become more or less popular over time - furniture, clothing, dishes, or even toys. We're going to use marbles because there are lots of them, they don't decay much over time, and there are many different sytles of them. The popularity of different styles of marbles changes over time.

The first task is to sort the marbles into piles based on their styles. Students using the interactive game can move a collection of about 30 marbles into piles based on their styles.

The students are then provided with a list of styles (e.g. smooth, striped, clay, glass, agate, yellow, purple, one color, two colors, etc.) and asked to label their piles and think about different ways that the marbles could be sorted.

The marbles are then shown grouped as marble collectors typically sort them. One grouping is by material (Glass, Agate, and Clay), and another is by patterns (Slags, Swirls, Earthenware, Agates, Rainbos, Onionskins).

A graph is shown with the numbers of marbles of each pattern type. Each junkyard has a graph of marbles found that is unique due to the popularity of the different marbles at different times.

The graphs can be used to help determine the order in which the junkyards were used. By sorting the junkyards so that the number of marbles of each style grows and then shrinks, you can see patterns in the data. This technique is based on the idea that marble styles go in and out of fashion over time.

As a style grows in popularity, the number of marbles of that style found in a junkyard should grow. As a style becomes less popular, less marbles of that style will be found. Based on this idea, you should be able to sort the junkyards into an order in which the number of each style of marble found grows then shrinks.

Students now rearrange the order of the graphs until the number of each style of marble follows the pattern of increasing and decreasing popularity.

Once the graphs are arranged so that the marble styles all follow the pattern, a relative order for the ages of the junkyards is determined. A problem that exists is that this method doesn't tell which junkyard is oldest because either end of the relative order could be oldest or youngest. What sorts of information could you use to figure out which junkyard is really the oldest?