Earth is composed of four main layers, starting with an inner core at the planet's center, enveloped by the outer core, mantle, and crust. The inner core is a solid sphere made of iron and nickel metals about 759 miles (1,221 kilometers) in radius.
source: nasa
South is downstream
Hope this helps
25,000 = 2.5 x 10^4
250 = 2.5 x 10^2
0.025 = 2.5 x 10^-2
0.00025 = 2.5 x 10^-4 :D
