The inner core of the earth is in a solid state whereas the outer core is in molten state.Give reasons.

The inner core and the outer core of the Earth are primarily composed of the same materials - iron and nickel. However, they exist in different states due to the varying pressures and temperatures they experience.

1. Pressure: The inner core is subjected to immense pressure because it is at the center of the Earth, with layers of rock and metal above it. This extreme pressure keeps the iron and nickel in a solid state, despite the high temperatures.

2. Temperature: The outer core, while still very hot, is not under as much pressure as the inner core. The lower pressure allows the iron and nickel to exist in a molten or liquid state.

3. Heat Transfer: The outer core is also where "convection" occurs. Heat from the inner core and the mantle causes the molten metal in the outer core to move in a circular pattern, creating Earth's magnetic field. This movement also helps to keep the outer core in a molten state.

4. Seismic Evidence: Seismic waves from earthquakes change speed, bend, or even stop when they hit different layers of the Earth. P-waves (pressure waves) can travel through both solid and liquid, but S-waves (shear waves) can't travel through liquid. When an earthquake occurs, P-waves have been observed to pass through the inner core, but S-waves do not, which suggests the inner core is solid and the outer core is liquid.