Answer:
a decrease in pressure
Step-by-step explanation:
A Divergent Limit occurs with the tectonic plates moving away in opposite directions and directions, so there is addition of magmatic material to the Earth's crust at this point. Magma ascends through a space that exists between the plates, called Rifte. At the divergent boundaries of the plates in the ocean, magma rises and melts because of a decrease in pressure caused by the removal of these plates.