If students have high-level understanding concerns about volcanoes, they can click on an always-available button marked ``Learn about volcanoes'' which will take them to the entrance to the ASK system.
The first time students go to this screen (Figure 2.12), which is called a ``zoomer,'' they see six top-level topics. A click on one of them, such as ``Tests,'' will take them to a list of general questions about this topic:
They can click any of these questions or return to the top-level topics screen. The zoomers quickly drop students into the part of the ASK network that they want to explore. Each of these questions has an answer movie, and each one of those answers has up to six followup questions.
Most ASK systems in GBSes are interlinked, which is to say that rather than being a hierarchy of questions, an ASK system is a web, with followup questions leading to other followups that, if students follow enough links, eventually lead back to the same questions again. This is so students can reach any part of the ASK system from any other part of the system.
As Volcano Investigator is a prototype rather than a full-fledged system, very little emphasis was made on designing the zoomers, but in many projects, ASK zoomers are a good way of presenting overview information to students and are designed very carefully.
In Sally's experience with Volcano, she asked about magma while running a test and was sent to this screen directly without going through the zoomers. Here, authors wanted to encourage students to explore this part of the GBS by directly linking it with the testing activity. Once they ask one of these ``non-local'' questions, students can either continue exploring the followup questions, go to the top-level zoomers, or go back to their testing screen.