Because it is constructed of dense, or heavy, components like as iron and nickel, the inner core is solid. Even when temperatures are extremely high, some materials do not "melt," and hence remain solid. The outer core is mainly liquid metal because it is composed of lighter elements such as oxygen and hydrogen. However, even here there is a solid component called the mantle that makes up more than 90% of the mass of Earth's shell.
The inner core forms first and floats to the top of the mantle where it melts due to the heat from below. This creates a fluid layer called the outer core which also floats on top of the mantle.
The outer core remains liquid at depths greater than about 1000 km while the inner core becomes solid at depths less than about 660 km. Thus, both cores become solid at different depths within Earth's structure.
Geologists used to think that the inner core was completely solid but now know that it contains regions of strong magnetic field called "magnetic bottles" which are similar to bubbles in water. These bottles are so strong that they resist melting even at depths of 1500 km or more.
Scientists think that the presence of these bottles may help control the flow of heat within Earth's interior by preventing material near the surface from sinking too far into the planet's center.
The inner core is a solid iron (Fe) and nickel alloy (Ni). The inner core is solid, despite the fact that it is hotter than the outer core due to the tremendous pressure. Heating occurs because of electrical resistance from the conductive iron and nickel alloy.
The inner core is the center of the earth and its existence is essential for understanding how the earth works. The inner core is about 1000 miles wide and 1500 miles deep. It extends down to about 6000 feet below sea level before it starts to thin out.
The outer core is a fluid consisting of ionized iron and nickel metal with some silicon and oxygen incorporated into their structure. The outer core forms a magnetic field that is responsible for geomagnetism. It ranges in depth from 30-60 miles but only averages 40 miles.
The boundary between the inner core and the outer core is called the "dynamic inner core boundary". Research has shown that the dynamic inner core boundary behaves like a liquid droplet when disturbed, which explains why earthquakes are usually confined to the inner core.
The outer part of the inner core is called the "fluid outer core" and it exists because heat is needed to create magnetic fields.
The inner and outer cores of the Earth are both formed of an iron-nickel alloy. Although the inner core is extremely heated, it is solid due to the extremely high pressure. The pressure in the outer core is insufficient to solidify it. However, due to its proximity to the inner core and heat from within, it too is melted rock that flows under the influence of gravity.
Melting of rock causes large volumes of water to be released into the atmosphere. This is why meteor showers are often associated with planetary alignments - when the Earth crosses through the path of a comet's tail, particles from the comet's nucleus enter the atmosphere and create rainbows over certain parts of the planet.
The alignment of planets with stars also influences the appearance of sunset colors because the angle at which sunlight strikes the Earth's atmosphere determines what wavelengths are visible to us. At sunrise and sunset, the sky is usually red because our view is blocked by the atmosphere as we look up at the sun. But during certain phases of the moon or between clouds, blue lights can be seen coming from the horizon, caused by refraction of light through layers of air with different temperatures. This is why stars have been used as nightlights for centuries - they produce a blue glow when lit from within our atmosphere.
Because of the great pressure exerted by the rest of the globe, the inner core remains solid. (Not just temperature but also pressure determine the condition of matter.) If the inner core was a liquid, it would cause the planet to collapse due to gravity.
The outer core is mainly made up of a mixture of iron and nickel with some carbons and other elements. It is a very dense material, almost as hard as steel. The inner core is mostly iron with some nickel and carbon. It is much more ductile than the outer core because it can be stressed for longer periods without breaking down.
The inner core is always being churned up by the moving plates beneath it, so there is constant motion within the core itself. This movement helps keep the core intact by preventing any one part of it from freezing into a solid block.
The outer core is stable enough that it cannot be melted by the heat from inside the planet, but it does get slightly heated by friction with the inner core.
Earth's inner core is its dynamic center; it is where all the movement of the planet is centered. The inner core is also the source of most earthquakes on Earth. As plates move under them, they create waves in the earth's crust.