Earth's internal structure. Cutaway artwork showing Earth's internal structure and layers to scale, with surface satellite imagery. The Earth's radius is 6371 kilometres (km). The uppermost layer is the crust (5 to 50 km thick), followed by the upper mantle (600 km thick), the lower mantle (2200 km thick), the outer core (2300 km thick) and the inner core (1220 km radius). Upper mantle hotspots include the volcanoes Mount Etna (upper right) and Mount Cameroon (centre right). Deep mantle hotspots include Hawaii (centre left) and the Mid-Atlantic Ridge (lower right). The Peru-Chile Trench (lower left) is a subduction zone causing volcanic activity in the Andes.