At https://phys.org/news/2020-07-idea-earth-outer-shell-broke.html … In this article we are told that it is well understood that volcanoes and earthquakes can be explained by the 50 year old theory of Plate Tectonics. This theory claims earth's outer shell, or lithosphere, is subdivided into plates that move relative to each other, concentrating most tectonic activity along the plate margins. Surprisingly, we are then told, the scientific community have no firm concept on how plate tectonics began. This month, July of 2020, a new explanation has been offered – published in Nature Communications. Apparently, the idea is that the lithosphere heated up. This caused expanision of the outer shell that generated cracks. The cracks grew in size and evolved into a global network of plates. Why the lithosphere didn't heat up on other occasions is left blank.
We are also told about one of the reasons why the expanding earth theory is dismissed. According to Charles Darwin, and other luminaries of an earlier time, tectonic activity and the distribution of the oceans and continents are explainable by an expanding earth. However, such simplistic ideas came a cropper with the theory the earth had a nuclear heat source. As radioactivity decays over time it implied there is less heat going forward. Hence, thermal expansion is less likely. Subsequently, the idea the earth expands was dropped, although a few rogue geologists still adher to the theory. In the new study they had to get round the thermal heat expansion problem, which they claim to be able to achieve. For the reasons behind their thinking one needs to go to the link above and read it fully. Suffice to say they are then able to generate heat – enough heat to cause the lithosphere to split apart = plate tectonics.
We may also wonder if the nuclear heat at the core of the planet is real or theoretical. It seems that electromagnetic activity with an origin in the sun plays a major role on earth. It has been suggested that this might even include tectonic events. Currently, this is fringe science, as is also the idea of an electric universe. One would have thought there would be extensive resistance to the idea of electricity in space as it would upset a lot of mainstream consensus thinking. However, NASA and other space research programmes from different countries, keep coming up with new facts that show giant filaments of electromagnetic around not just solar systems, but galaxies. If all that is required is thermal expansion to set in motion an expanding earth we are into a different ball game. After all, mainstream contend that the universe is expanding. Not only that but black holes are thought to be expanding too. Why not stars and planets?
Note … I'm not advocating an expanding earth model, merely exercising my imagination. When, and if, we get to read up on some of the expanding earth literature, one is left thinking it has a lot to be desired. You don't get a eureka moment. Never the less, it is a theory, and Plate Tectonics is itself a theory. It was once a well respected theory if Charles Darwin thought it was feasible. Nowadays, Plate Tectonics is fashionable, and embedded into the uniformitarian model. It may not always be the apple of Big Daddy's eye.