Plate Tectonics. The Earth’s 4 Layers 1.Inner Core: Center, made of solid iron and nickel. 1200 km 2.Outer Core: Made of liquid iron and nickel. 2250.
Mt. Fuji, Japan The Theory of Plate Tectonics Steps in Development 1. Benjamin Franklin (late 1700s) Recognized that crust of Earth was a shell. Surface.
