What phenomenon is caused by divergent tectonic plates moving apart from each other?

The phenomenon caused by divergent tectonic plates moving apart from each other is mid-ocean ridge formation. When tectonic plates diverge, magma from the mantle rises to fill the gap created by the separating plates. As this magma cools and solidifies, it creates new oceanic crust, forming a mid-ocean ridge.

Mid-ocean ridges are underwater mountain ranges that spread across the ocean floor, characterized by a rift valley at the center where the plates are pulling apart. This process not only results in the creation of new crust but also can lead to increased volcanic activity along these ridges. The geological activity associated with divergent boundaries plays a pivotal role in shaping the landscape of the ocean floor and contributes to the plate tectonics of the Earth.

Other options describe different geological phenomena: earthquakes are typically associated with the friction and movements at plate boundaries, volcanic eruptions can occur at convergent boundaries or at hotspots, and tsunamis are large ocean waves typically caused by undersea earthquakes or volcanic eruptions, not directly from the movement of plates apart.