* Temperature: The deeper you go in the Earth, the hotter it gets. This is due to the heat from the Earth's core and the decay of radioactive elements within the Earth.
* Pressure: Pressure also increases with depth. Increased pressure raises the melting point of rocks.
* Composition: Different types of rocks have different melting points. Rocks rich in silica (like granite) melt at lower temperatures than rocks rich in iron and magnesium (like basalt).
* Presence of water: Water can lower the melting point of rocks. This is why volcanic eruptions often occur near subduction zones where water is dragged down into the Earth's mantle.
General Range:
While the melting point varies, rocks typically start to melt at depths between 100 and 150 kilometers (60-90 miles). This region is known as the partially molten zone, where rocks are partially melted, creating a mixture of solid and liquid rock called magma.
Specific Examples:
* Basalt: A common volcanic rock, basalt typically melts at around 1200°C (2190°F) at surface pressure. However, at depths of 100 km, the pressure increases, raising the melting point to around 1450°C (2640°F).
* Granite: A silica-rich rock, granite melts at lower temperatures than basalt. At surface pressure, it melts at around 650°C (1200°F). However, at depths of 100 km, the pressure raises the melting point to around 900°C (1650°F).
Important Note: The actual melting point of rocks in the Earth's interior is a complex process influenced by many factors. Scientists use sophisticated models and experimental data to study these processes.
