Why does the "Ring of Fire" pretty much define "Pacific Rim"

Question

The Pacific Rim is pretty much defined by the so-called "Ring of Fire." It consists of the "stomping ground" for a disproportionate number of earthquakes and volcanoes, and the affected territory extends up and down the coast of North and South America, up and down the East Asian coast, and into the "Australasian" islands like Indonesia, the Philippines, and New Zealand. Apparently it has something to do with the presence (or absence) of tectonic plates there.

Why is there such a configuration of tectonic plates, and the resulting earthquakes and volcanoes in the Pacific, and not to the other oceans?

Answer 1

There isn't a concentration of tectonic plates - rather the opposite!

The "Ring of Fire" is a pattern really. It is marked by subduction zones. So the question becomes, "Why is the Pacific Ocean surrounded by subduction zones?".

Think back to Pangaea. This was a supercontinent that formed in the late Palaeozoic. Virtually all of the Earth's land masses were concentrated in one large supercontinent. When this broke up, the new continents moved away from each other. Fast forward 200Ma or so, and you find that the continents have moved so far apart that they are now converging on a point on the other side of the planet - the continents are moving towards each other! Hence the remains of the super ocean (which was actually multiple ocean plates - today's Pacific & Nazca plates, plus the Farrallon plate (RIP),etc ) is shrinking as the continental plates move towards it. This destruction of the ocean plate(s) occurs at subduction zones.

This is a big picture generalisation. Not all of the Pacific's boundaries are marked with subduction zones (e.g. North America has two large strike slip systems + a new spreading ridge). Also, not all of the continents are converging on each other. Africa is doing a pirouette, India is moving northwards, etc.