Your bands may have a recognizable sequence: narrow, wide, narrow. A pattern can help join two pieces when part of that sequence appears in both.

Many trees make a growth ring each year. Rings may differ in width. But simply counting is not always enough. A ring can be missing, unclear, or misleading. Researchers compare patterns rather than assuming every visible line supplies a perfect year.

The University of Arizona describes crossdating, matching ring patterns between samples and dated sequences. A dated reference connects a pattern with calendar years. Without that anchor, a matching pattern can show an overlap without naming the year.

Our drawing uses invented bands and pretend reference years. It lets you try matching, not date a real tree. Find the repeated part before reading the model years. A wide band is a clue in a pattern, not proof of one exact cause or a rule that works for every tree everywhere.

Stack your paper layers in order. In this undisturbed model, the bottom paper was placed before the one above it. That is a relative order: earlier compared with later. It is not a calendar date.

A person could put an old object into a newer layer. Layers can also be disturbed. So "lower" is not a safe shortcut to every object’s manufacture date. Researchers need to inspect the setting.

Another method is radiocarbon dating, a way to estimate the age of suitable once-living material from changes in a form of carbon. The National Park Service describes its use for samples up to about 50,000 years old. Results have uncertainty, not a perfect birthday.

A paper stack cannot perform that test. Nor does radiocarbon directly date any rock or metal you choose. Different materials and questions need different clues. Ask whether a result gives order, a calendar estimate, or only a possible connection.

together · About 8 minutes; estimate

You need

• Printed invented pattern or paper
• Pencil

Try it

1. Use the printed model or copy its two band patterns.
2. Ignore the years first; find where the narrow/wide sequence repeats.
3. Circle the overlap in both rows.
4. Now use reference years 2001 to 2006 to label the second row’s matching bands.
5. Assign 2007 to its next band in this tidy model.
6. Record why the invented reference matters and one limit.

together · About 5 minutes; estimate

You need

• Three paper sheets
• Large paper object drawings
• Pencil

Try it

1. Label a drawing old object; all clues are invented.
2. Stack papers one at a time and record the placement order.
3. Place the old-object drawing on the newest top layer.
4. Ask whether its layer makes the object newly made.
5. Move another drawing between layers to model disturbance.
6. Record which ordering claims now need more evidence.