* Increased Pressure and Temperature: The pressure and temperature increase significantly as you go deeper. At 200km, the temperature is estimated to be around 1000-1200°C, and the pressure is immense.
* State of Matter: The rocks are no longer solid like those on the surface. Due to the immense pressure, they are in a state called solidus, where they act like a very viscous fluid. Think of it like very thick honey.
* Mineralogical Changes: The minerals within the rocks are altered by the extreme heat and pressure.
* Rock Type: The dominant rock type at this depth is peridotite, a dark, dense rock rich in olivine and pyroxene.
What doesn't happen:
* Melting: While the rocks are very hot, they don't fully melt. The immense pressure prevents this.
* Sudden Change: The transition from solid to "solidus" isn't a sharp boundary. The change in rock behavior is gradual as you go deeper.
Important Note: The exact conditions and rock behavior at 200km can vary depending on location and geological factors.
