Mount Everest is the highest mountain on Earth above sea level, but it is not the world’s tallest. That honour goes to the Hawaiian volcano Mauna Kea. When measured from its base on the Pacific Ocean floor, it is about 1,000 metres taller than Mount Everest. Mauna Kea is part of a 5,600-kilometre-long chain of volcanoes stretching westward from the main Hawaiian island. This volcanic chain is formed by small convection streams called “hot spots”, just below the Earth’s crust, where magma rises from the hotter parts of the mantle, the region between the crust and the core of the earth. These hot spots melt sections of the tectonic plates moving above them, causing magma and bits of the molten plate to erupt onto the sea floor. Over time, the lava accumulates, forming a mountain that rises above sea level. The moving tectonic plates carry the newly-formed mountain away from its original location, as newer volcanoes continue to form in the same spot.