Fine-grained dark igneous rock. Continental Crust is 30 - 50 km thick. Mantle - solid rock that flows under high pressures and temperatures. About 3000 km thick. Outer core is molten iron and nickel.
Inner core is solid iron and nickel.
The Earth's magnetic field is generated by rotation of inner core and convection in outer core. Magnetic field also responsible for aurora borealis . Charged particles from sun follow magnetic field lines. Particles collide with molecules in atmosphere and cause them to emit light. Travel through solid and liquid.