Magnesium and calcium belong to the second group i. e. alkaline earth metals. They are known as earth metals because they are extracted from the earth. They are very reactive elements. Their reactivity increases when we go from top to bottom because the outermost electrons goes farther from the nucleus i. e. atomic radius increases so less energy is needed for its removal.
The Pacific plate is subducting beneath the Philippine Sea plate to the east while the west/northwestern part of the Philippine Sea plate is subducting beneath the continental Eurasian plate.
