 Okay, so we're talking about plate tectonics. That's the all-encompassing model that explains most of surficial processes on Earth. And in this model, we have a viscous flowing mantle, which is convecting. And on top of that, we have crustal material, which is moving around. We have places where we're making oceanic crust, called divergent boundary, because the crust is diverging. And then when it meets another piece of brittle surficial crust, whether it be continental or oceanic, one of them will subduct. So that will be a convergent margin. And most of the action on Earth is happening at these boundaries, either at the divergent boundaries where basalt is coming up from the mantle, the mantle is very shallow and we're forming new crust, or at the places where we're converging, and then we have subduction. Now, subduction zones are the most exciting places on Earth because we make mountains there, and we have plates that are sliding either completely perpendicular one to the other, or they have some strike-slip movement, so they're moving laterally next to each other. When we do that, we have a mixture of that. Like, for instance, California, the Pacific plate is not going straight under, it's coming south like this, and it's pulling like that. So what happens is, as the down-going slab builds up stress because there's friction there, and it's not moving, it builds up, it builds up until it releases. That release is called an earthquake. So all of the big earthquakes on Earth happened at convergent boundaries. There are other places where we get them, for instance, the divergent boundaries, there are small earthquakes, there are earthquakes in a number of places, but the big ones, the San Andreas Fault, the Fault in Indonesia that made the tsunami, the Alpine Fault in New Zealand, these are all at those sorts of places where we have convergent boundaries. Now, I mentioned tsunamis, and tsunamis are really large waves that get triggered by a number of processes, and the most usual one is simply that. We have one of those movements that's underwater, and that sets a wave up, like the Indonesian one, 10 years ago on Boxing Day that was such a catastrophe. That was exactly to slip on a convergent margin that triggered a big earthquake that made the wave. It's not the only way to make tsunamis. It's interesting that at convergent boundaries, because the slab goes down, dehydrates, flux is melting in the mantle wedge, above that point we get magmas rising, and we have volcanic-orthical arcs there. These can be on continents, like in the Andes, or they can be in oceans like the Japan arc, but either way, they're volcanic material that can erupt. Now, when these volcanoes build up, they can, A, be very explosive and put a lot of ash in the air, affecting climate for years, decades, even more, but also you can have big slumps coming off of these volcanoes that can go into the ocean and trigger a tsunami. So those are sort of the two ways that tsunamis are triggered. One is via earthquakes, one is via huge landslides coming off of volcanoes. That's the connection I wanted to make was the connection between subduction, which is simply part of the plate tectonic cycle, where we make crust, we destroy it, we put it back in the mantle and we keep recycling it to keep things sort of at a steady state. So we make crust and we destroy it, and that destroying it process is quite exciting, quite interesting, it does some fun things.