Tectonic plates is a theory that the lithosphere is separated into plates that move over the asthenosphere, the molten upper portion of the mantle. Oceanic and continental plates come together, spread apart, and interact at boundaries all over the planet. Tectonic plates float on top of the molten rock and moving around the planet. The heat from radioactive processes within the planet's interior causes the plates to move, sometimes toward and sometimes away from each other. This movement is called plate motion, or tectonic shift.
Tectonic plates are the reason why Earths surface is shaped the way that it is. You may not see it but there’s lots of activity going on below where you stand. The Earth is composed of 5 parts. The inner core, outer core, asthenosphere (which includes the mantle) and the lithosphere. To answer your question, the tectonic plates “float” on the Earths surface because of the convection currents located in the mantle. The mantles magma is always heated and in a liquid state. Just like a lava lamp, heat currents rise... then fall back down and rise again.. like a constant circle. This motion is always happening which is why the lithosphere (Earths crust) appears to be changing overtime.
this is kinda controversial so yeah. anyways, this was one of the deepest and was kinda small when archeologist found it. they think it was on earth about 231 million years ago.
