The studying of the fossils, land features, and climate patters all around the globe, in the deeper layers of the ground, have presented undoubted evidence that a super-continent, Pangea, existed in the distant past. Fossils from the same types of animals and plants without any changes in appearance in the different parts have been found on all continents, and if they were not merged, there's just no way that an animal or plant will be totally same in different regions, isolated from on another. Also, the climate patters show that in certain period of the geological past, the climate had been pretty much the same on every continent, and that is impossible if they are set apart. The land features also suggest that the continents have been merged, as they perfectly match each other, even though nowadays they are far away from one another.
The mid ocean ridges are the places were the new crust is formed from the emerging magma from the mantle. The older crust is pushed sideways as the new one is formed, and that process continues all the time. This is possible because the mid ocean ridges appear on divergent boundaries, so the pressure, temperature, and magma from the mantle manage to break through upwards easily.
