From Simple English Wikipedia, the free encyclopedia
The
inner core
is the very center of the
Earth
, and the hottest part of the planet. It is a mainly a
solid
ball with a
radius
of about 1,220 km (760 mi), according to
seismological studies
.
[1]
[2]
It is believed to consist mostly of an
iron
?
nickel
alloy
and to be about the same temperature as the surface of the
Sun
: about 5700
K
(5400 °C).
[3]
The inner core was discovered by
Inge Lehmann
in 1929, using
seismology
. Lehmann was studying a large
New Zealand
earthquake. An
earthquake
makes vibrations which move through the inside of the Earth. The vibrations Lehmann studied seemed to be moving across something solid in the center of the planet. She called this the
inner core
. She wrote about it for many years, but it was not proved to exist until 1970.
The inner core is more than 5,000 kilometers below the earth's surface. The pressure in Earth's inner core is about 3,500,000
atmospheres
.
[4]
Iron can only be solid at such high temperatures because its melting temperature increases dramatically at such pressures.
[5]