Answer: 
Five billion years ago the Earth was
formed by a massive conglomeration of space materials. The
heat energy released by this event melted the entire planet,
and it is still cooling off today. Denser materials like
iron (Fe) sank into the core of the Earth, while lighter
silicates (Si), other oxygen (O) compounds, and water rose
near the surface. The earth is divided into four main layers:
the inner core, outer core, mantle, and crust. The core
is composed mostly of iron (Fe) and is so hot that the outer
core is molten, with about 10% sulfur (S). The inner core
is under such extreme pressure that it remains solid. Most
of the Earth's mass is in the mantle, which is composed
of iron (Fe), magnesium (Mg), aluminum (Al), silicon (Si),
and oxygen (O) silicate compounds. At over 1000 degrees
C, the mantle is solid but can deform slowly in a plastic
manner. The crust is much thinner than any of the other
layers, and is composed of the least dense calcium (Ca)
and sodium (Na) aluminum-silicate minerals. Being relatively
cold, the crust is rocky and brittle, so it can fracture
in earthquakes. (Univ. of Nevada)
This is a brief summary of our knowledge
of the earth's interior. For further information, see:
University
of Nevada |
