Here's how it works:

* Tributary glaciers are smaller glaciers that flow into larger, main glaciers.

* Erosion: Tributary glaciers erode the landscape at a shallower rate than the main glacier due to their smaller size and volume.

* Elevation: The main glacier carves a deeper valley than the tributary, leaving the tributary valley hanging higher up the mountainside.

* Waterfall: When the tributary glacier melts, it leaves behind a dramatic drop, or waterfall, where the tributary valley meets the main valley.

Other features formed by tributary glaciers:

* Cirques: Bowl-shaped depressions at the head of a glacier.

* Aretes: Sharp ridges that form between cirques.

* Horns: Sharp peaks formed where multiple cirques intersect.

In summary: Hanging valleys are a striking example of the erosive power of glaciers, showcasing the interplay between tributary and main glacier activity.