There are at least two ways to express the geological significance of the Ring of Fire.
First, we can say that this area is geologically significant because it is so very seismically active. This is an area of the world that is home to the majority of all the volcanoes in the world. It is also where the majority of all the earthquakes in the world occur. This means that it is very significant for geologists because they can observe a variety of seismic activity.
Second, we can say that this area is geologically significant because of its plate tectonics. The seismic activity discussed in the previous paragraph is caused by plate tectonics. There are subduction zones on both sides of the Ring of Fire. As the oceanic plates slide under the continental plates, volcanoes are created as well as tensions that can lead to earthquakes.
Thus, the Ring of Fire is geologically significant because of its plate tectonics and the seismic activity that the plate tectonics cause.