What do closely spaced contour lines on a topographic map indicate

Closely-spaced contour lines indicate a steep slope, because elevation changes quickly in a small area. In contrast, broadly spaced contour lines indicate a shallow slope. Contour lines that seem to touch indicate a very steep or vertical rise, like a cliff or canyon wall.

from google :

The Ring of Fire is a ring of volcanoes around the Pacific Ocean that result from subduction of oceanic plates beneath lighter continental plates. Most of the Earth's volcanoes are located around the Pacific Ring of Fire because that the location of most of the Earth's subduction zones

does this help?.