Earth's surface is not one solid piece — it's made of huge slabs called «tectonic plates» that float very slowly on a semi-molten rock layer below. Sometimes these plates move or suddenly rub against each other, shaking the ground in what we call an «earthquake».
A «volcano» is a mountain with extremely hot melted rock underneath, called «magma». When pressure builds up underground, this molten rock pushes upward and erupts from the volcano's opening as hot «lava», sometimes along with smoke and ash.
Scientists build special instruments to monitor earthquakes and volcanoes, warning people early and helping them prepare, because these two events are among the most powerful natural happenings on our planet.
