down to around 3,000 miles liquid iron and nickel iron-nickel core Earth’s interior Inside the Earth, USGS structure of the earth around 1,800 miles below the surface http://pubs.usgs.gov/gip/dynamic/inside.html Inside the Earth [This Dynamic Earth, USGS] http://pubs.usgs.gov/gip/dynamic/inside.html Overall interior structure of the Earth Earth's crust http://pubs.usgs.gov/gip/dynamic/inside.html increase http://pubs.usgs.gov/gip/dynamic/inside.html http://pubs.usgs.gov/gip/dynamic/inside.html USGS Layers of the Earth http://pubs.usgs.gov/gip/dynamic/inside.html Earth’s interior liquid iron and nickel Earth’s interior Inside the Earth [This Dynamic Earth, USGS] http://pubs.usgs.gov/gip/dynamic/inside.html down to around 3,000 miles http://pubs.usgs.gov/gip/dynamic/inside.html http://pubs.usgs.gov/gip/dynamic/inside.html structure of the earth Inside the Earth [This Dynamic Earth, USGS] Inside the Earth [This Dynamic Earth, USGS] USGS: Layers of the Earth Inside the Earth http://pubs.usgs.gov/gip/dynamic/inside.html USGS USGS Dynamic Earth liquid iron and nickel http://pubs.usgs.gov/gip/dynamic/inside.html increase outer core is a layer of molten iron and nickel around 1,800 miles below the surface http://pubs.usgs.gov/gip/dynamic/inside.html Inside the Earth increase http://pubs.usgs.gov/gip/dynamic/inside.html USGS United States Geological Survey (USGS) illustration