What exactly causes huge plates to move and collide with such a colossal force? How do they not create extremely wide trenches in places where they move apart? Why isn’t the place where they move apart just molten magma? What is the force propelling magma and ash upwards during an eruption? I searched on the Internet, but I want a deeper explanation, which I couldn’t find. TIA!
In: 1
The earth was formed when a bunch of rocks collided with each other. Those collisions caused a lot of heat just from the large forces involved. The only way for heat to escape is through radiation into space, which is pretty inefficient. So much of the heat from way back then is still trapped beneath the crust and is the engine that drive these processes.
The heat is greatest at the core. So magma near the core is hotter than magma near the crust. Hotter things are less dense, so that hotter magma starts rising and the colder magma starts sinking. As the hotter magma rises, it starts cooling down because it’s further away from the hot core. And vice versa for the cool magma sinking down. This cycle of rising and sinking causes massive currents. The Earth’s crust is just a bunch of little rafts riding these currents.
> How do they not create extremely wide trenches in places where they move apart?
They do. There’s the [East African Rift](https://en.wikipedia.org/wiki/East_African_Rift) on land and the [Mid-Atlantic Ridge underwater](https://en.wikipedia.org/wiki/Mid-Atlantic_Ridge). Tectonic plates just move really slow, millimeters per year. And lava solidifies basically instantly. So new rock basically fills the gap very quickly. In the Atlantic, it’s filling the gap so quickly it’s formed a mountain range instead of a trench.
Latest Answers