What term is used for the activity that includes the movement of magma toward or onto the Earth's surface?

The term that describes the movement of magma toward or onto the Earth's surface is volcanism. This process includes not only the ascent of magma from the mantle through the crust but also the eruption of this material, resulting in volcanic activity. Volcanism is a key part of the rock cycle and significantly shapes the Earth's surface through the formation of volcanic landforms, such as mountains, islands, and plateaus.

Other terms listed, such as seismology, refer to the study of earthquakes and seismic waves rather than magma movement. Erosion pertains to the process of wearing away rocks and soil due to natural forces like wind or water, which is unrelated to volcanic activity. Tectonics involves the movement of the Earth's plates and how these movements lead to geological features and events, but it doesn't specifically encompass the behavior of magma itself. Thus, volcanism is the most accurate term for the activity of magma moving toward or onto the Earth's surface.