Jump to navigation Jump to search Structure of Earth The Earth's core is the part of Earth in the middle of our planet. It has a solid inner core and a liquid outer core.
Discovery[ edit ] The Earth was discovered to have a solid inner core distinct from its molten outer core inby the Danish seismologist Inge Lehmann who deduced its presence by studying seismograms from earthquakes in New Zealand.
She observed that the seismic waves reflect off the boundary of the inner core and can be detected by sensitive seismographs on the Earth's surface. This boundary is known as the Bullen discontinuity,  or sometimes as the Lehmann discontinuity.
Dziewonski and Gilbert established that measurements of normal modes of vibration of Earth caused by large earthquakes were consistent with a liquid outer core. At the earths core edit ] The Earth's inner core is thought to be slowly growing as the liquid outer core at the boundary with the inner core cools and solidifies due to the gradual cooling of the Earth's interior about degrees Celsius per billion years.
Even though it is growing into liquid, it is solid, due to the very high pressure that keeps it compacted together even if the temperature is extremely high.
It was even suggested that Earth's inner core might be a single crystal of iron. This variation is surprising, since lateral temperature variations along the inner-core boundary are known to be extremely small this conclusion is confidently constrained by magnetic field observations.
Because the inner core is not rigidly connected to the Earth's solid mantlethe possibility that it rotates slightly more quickly or slowly than the rest of Earth has long been entertained.
Estimates of this super-rotation are around one degree of extra rotation per year. Growth of the inner core is thought to play an important role in the generation of Earth's magnetic field by dynamo action in the liquid outer core. This occurs mostly because it cannot dissolve the same amount of light elements as the outer core and therefore freezing at the inner core boundary produces a residual liquid that contains more light elements than the overlying liquid.
This causes it to become buoyant and helps drive convection of the outer core. This may be necessary to explain why seismic waves pass more rapidly in some directions than in others. Yoshida and colleagues proposed a novel mechanism whereby deformation of the inner core can be caused by a higher rate of freezing at the equator than at polar latitudes,  and S.
Karato proposed that changes in the magnetic field might also deform the inner core slowly over time. There is a model which explains this by differences at the surface of the inner core — melting in one hemisphere and crystallization in the other. This may lead to enhanced magnetic field generation in the crystallizing hemisphere, creating the asymmetry in the Earth's magnetic field.
History of Earth Based on rates of cooling of the core, it is estimated that the current solid inner core started solidifying approximately 0.
If true, this would mean that the Earth's solid inner core is not a primordial feature that was present during the planet's formation, but a feature younger than the Earth the Earth is about 4.Iron is a relatively dense element under normal conditions, and under the extreme pressure at the Earth's core it would be crushed to an even higher density, so an iron core would account for all.
A century ago, science barely knew that the Earth even had a core. Today we are tantalized by the core and its connections with the rest of the planet.
Indeed, we're at the start of a golden age of core studies. We knew by the s, from the way Earth responds to the gravity of the Sun and Moon. May 17, · “At The Earth’s Core,” first published in , is one of Edgar Rice Burrough’s most imaginative works.
It is the first of seven books in the Pellucidar series and imagines a world inside the earth (five hundred miles beneath the surface) where the most advanced species is reptilian and the humans are still living in the stone age/5().
The inner core is solid, but the outer core is a hot liquid. Scientists think that movements of metal, like currents in the oceans, create the magnetic field that surrounds the Earth.
Oct 09, · Earth's Interior. Earth's interior is made up of a series of layers that sit below the surface crust. In order of depth, these layers include the solid, but flowing mantle, the liquid outer core. Iron is a relatively dense element under normal conditions, and under the extreme pressure at the Earth's core it would be crushed to an even higher density, so an iron core would account for all.