What is the difference between magma and lava?

The distinction between magma and lava is fundamental in geology and relates to their locations and characteristics during different stages of an eruption. Magma is the molten rock that exists beneath the Earth's surface. It forms from the melting of rocks in the mantle and crust under high pressure and temperature. When magma reaches the Earth's surface during a volcanic eruption, it is then referred to as lava.

This definition highlights the transition of magma to lava, which is a significant aspect of volcanic activity and the rock cycle. Understanding this distinction helps clarify different geological processes, such as the formation of volcanic landforms and the behavior of materials during eruptions. Knowing that magma is the substance underground and lava is its above-ground counterpart allows for a better understanding of volcanic events and their impacts on the environment.

The other options do not accurately capture this important relationship. The position of magma relative to the surface and its gaseous content varies, but defining them by location, gas content, or cooling rates does not encompass the essence of their definitions as clearly as recognizing one as the precursor to the other.