Asia has the highest average elevation of the continents and contains the greatest relative relief. The tallest peak in the world, Mount Everest, which reaches an elevation of 29,035 feet (8,850 metres; see Researcher’s Note: Height of Mount Everest); the lowest place on Earth’s land surface, the Dead Sea, measured in the mid-2010s at about 1,410 feet (430 metres) below sea level; and the world’s deepest continental trough, occupied by Lake Baikal, which is 5,315 feet (1,620 metres) deep and whose bottom lies 3,822 feet (1,165 metres) below sea level, are all located in Asia. Those physiographic extremes and the overall predominance of mountain belts and plateaus are the result of the collision of tectonic plates. In geologic terms, Asia comprises several very ancient continental platforms and other blocks of land that merged over the eons. Most of those units had coalesced as a continental landmass by about 160 million years ago, when the core of the Indian subcontinent broke off from Africa and began drifting northeastward to collide with the southern flank of Asia about 50 million to 40 million years ago. The northeastward movement of the subcontinent continues at about 2.4 inches (6 cm) per year. The impact and pressure continue to raise the Plateau of Tibet and the Himalayas.