From the dramatic-looking title screen to the worried mayor presenting his case, the entire point of the introduction sequence is to attract students and make them feel like there is some problem they personally need to solve. Although it's clear that this volcano isn't real, this isn't an abstract discussion of geology or a magazine article about how the US Geological Survey does its job. This is a volcano with thousands of people who need an answer from you that could well save their lives.
The introduction consists of a series of screens (mostly digitized photos and art drawn by artists). In Volcano, there are two screens: the ``attract'' mode (the flashy title screen) and the lava flow (where the co-worker sets the students up to do their work).
The movies are carefully edited to keep the talking to a minimum. GBSes in general are designed to emphasize the urgency of the mission to keep students' attention. As such Volcano is ideal--Mt. Andrews is a clearly dangerous menace that needs to be explored. Geology taught in a lecture might seem abstract--who needs to know about the molten mantle of the earth? Here, the molten mantle is directly threatening people's lives, and purpose of the information that the student is learning is made clear.
There is little learning going on in the introduction--the contents of the movies are largely a set up for the scenario, which means it sets up the fictional details of this particular volcano and the background information students need to know. It also outlines their goal: prepare a report that tells the mayor what to do, balancing the need for safety with the expense and financial loss that a evacuation would cause.