Why is one rock melting, while the other is solid at the same ...

[kaid0807]

Why is one rock melting, while the other is solid at the same depth and temperature?
 
  Please explain what causes one of the rocks to melt and not the other. Hint: What does the title of one of the graphs suggest has been added to the system?
  What will be an ideal response?

Question 2

What is a geothermal gradient? Given an average geothermal gradient for continents and a surface temperature of 15C, what is the temperature at a depth of 10 kilometers?
 
  What will be an ideal response?

[izzat]

Answer to Question 1

Rock Y is melting whereas rock X is not because melting temperature at a particular pressure is lower in the presence of water (wet melting) than in the absence of water (dry melting).

Answer to Question 2

The geothermal gradient is the increase in temperature that occurs with the increase in depth below Earth's surface. Using an average of 25C/km, then at 10 km depth the temperature would be 265C (15 at the surface + (10 km)(25 C/km)).

[kaid0807]

Thank you

[izzat]

Happy to help you