Why are the asthenosphere rocks mostly molten?​

The asthenosphere is a region in the Earth's mantle that lies beneath the lithosphere. While the rocks in the asthenosphere are not entirely molten, they are partially molten or exist in a semi-fluid state. This semi-fluidity of rocks in the asthenosphere is due to several reasons:

1. Temperature and Pressure: The asthenosphere is located at depths below the Earth's surface where temperatures are significantly higher compared to the overlying lithosphere. Increased temperature, combined with high pressure from the weight of the Earth's layers above, causes rocks in the asthenosphere to be partially molten.
2. Heat from the Earth's Interior: The heat generated from the Earth's interior, primarily from the decay of radioactive elements and residual heat from the planet's formation, contributes to raising the temperature of rocks in the asthenosphere, promoting partial melting.
3. Mineral Composition: The minerals present in the rocks of the asthenosphere have specific melting points. At the high temperatures and pressures of the asthenosphere, some minerals may reach their melting points, causing partial melting while still maintaining a solid state overall.

It's essential to note that the asthenosphere is not entirely molten like the outer core; rather, it's a semi-fluid layer where rocks are ductile and have the ability to flow slowly over long periods of time, providing the necessary "plasticity" for the movement of tectonic plates. This semi-fluid nature allows the lithospheric plates to move and slide over the more ductile asthenosphere, leading to plate tectonics and the movement of continents.