QQQ has huge tech exposure, but it is not a 'tech fund' in the pure sense either. The fund's arcane weighting rules further distance it from anything close to plain vanilla large-cap or pure-play tech coverage.
During the time when Earth was forming and was in a molten state, heavy materials like iron and nickel sank to the center of the Earth's mass and lighter materials floated to the surface of the mass. The very center of what we call the core, is solid in the middle because of the increased pressure in that region.
Material at a similar distances from the Sun collided together to form each of the planets. Earth grew from material in its part of space. Materials collided, collisions caused Earth to heat up. Rock & metal melted, molten material separated into layers creating the crust, mantle, and both the cores (inner and outer).