Final answer:
Magma surrounded by rock cools slower due to the insulating properties of rock. Exposure to air or water leads to faster cooling because they are better conductors of heat and can absorb heat more quickly.
Step-by-step explanation:
The question addresses the concept of heat transfer in geology and physics. When magma is surrounded by rock, it cools slower compared to when it is exposed to air or water.
This is because wall rock insulates the magma well, reducing the rate of heat loss. In contrast, air and water are better conductors of heat, which means they can absorb heat from the magma more quickly, leading to faster cooling.
Specific heat capacity plays a significant role in this process; materials with higher specific heat capacities can absorb more heat before their temperature increases significantly.