What is the part of the earth that makes up most f its mass?
The earth's inner core is composed of solid or semi-solid iron and nickel, which then becomes a viscous liquid to form the outer core.
This build-up of iron constitutes most of the mass of the earth
It has long been theorized that earth was composed of various layers of material with rather uniform boundaries. In the late 1600's it was suggested that the center of the earth was hollow.
Scientists now believe it is a solid-like core of iron which because of its greater density migrated to the center of the planet. The volatility of the minerals was due to the extreme heat of the colliding materials along with nuclear energy resulting from radioactive elements. This idea is based on measurements of seismic activity, earthquake waves and densities of materials.
New stuff - if you need the perfect 3D model of inner earth, find a close to spherical round shape avocado, preferably with lots of bumps on its skin. When you cut it in half and pull it apart you will see the earth's layers. The skin representing the earth's crust, then the tasty eating part representing the earth's mantel, then the pit, representing the earth's core.
Surprisingly, these three layers are displayed by the avocado in fairly close proportions to those theorized for the earth.