Answer:
An extreme version of scoria occurs when volatile-rich lava is very quickly quenched and becomes a meringue-like froth of glass called pumice. Some pumice is so full of vesicles that the density of the rock drops low enough that it will float
Explanation:
A hot spot is here magma appears near to the surface. Imagine this, the crust is a plate, and the hotspot is a pencil, as the plate moves, you punch holes through the plate. This is the hotspot creating volcanoes as the crust moves. This is how hotspot volcanoes are created. The volcanoes that are created on boundaries are created from differences in the crust as it is created.
I'm pretty positive its ecosystem. I hope this helps :)
