Why Should I Care about Mud Volcanoes from the Mantle?
Curiosity may have killed the cat, but it made a scientist of him first!
The best scientists in the world are 8-year-old kids. They want to find out why things are the way they are. They want to poke things and take them apart to see how they work and what they will do if you change something about them. Curiosity is a powerful motive for everything these young scientists do. People who keep feeling this way about things around them often end up as scientists when they grow up. We scientists wonder about why these seamounts are here, how they formed, how old they are, how often they "erupt," what the fluids in the muds contain, what exactly are the chemical reactions that released the fluids from the subducting plate, why do we find creatures living at the mouth of the conduit at the tops of some of the seamounts (and why don't we find them at others?) and a whole lot of other things. The answers to these types of questions tell us about things that affect not only the seamounts, but also our lives and those of other creatures.
So what is it they can they tell us?
They can tell us about why earthquakes happen. The mud volcanoes permit us to find out about how the subducting plate alters as pressure increases and as changes in temperature affect it. This is important because the changes in the physical conditions of the subducting plate affect the way it interacts with the over-riding plate. This, in turn, influences how often earthquakes take place at the boundary between the top of the subducting plate and the bottom of the over-riding plate and how big the earthquakes may be. For instance, some scientists studying the earthquakes that happen in subduction zones believe that if a lot of serpentine is present in the subduction zone then few earthquakes (and only small earthquakes) will occur. This is because serpentine is pretty "slippery" stuff. It can't take too much stress without breaking. So a subducting plate that is being over-ridden by a plate that has a lot of serpentine at the bottom of it would not have many big earthquakes. Parts of the Mariana subduction zone have few large earthquakes. This is not true for the area around Guam, but there is a different reason for that. There was a very large earthquake (~ magnitude 8) back in 1993 that caused a lot of damage on Guam and a small tsunami (sometimes called "tidal waves" although they have nothing to do with the tides). A tsunami is a series of large waves that form when there is a change in the seafloor surface (they can innundate coastal areas and can cause widespread property damage and loss of life).
So, we can see that the physical conditions of the subduction zone are important things to know about if we want to understand patterns of earthquakes in space and time. We also want to know whether (as we suspect) the seamounts are related to earthquake activity taking place in the subduction zone and in the over-riding plate. Some of the seamounts that we think are "active" (are having eruption events right now or have had them very recently) have had earthquakes recently and others have not. We don't know why some do and some do not, but we are trying to figure this out.