Additionally, some maps contain
circular outlines; these features represent volcanic
calderas and
central volcanoes (Einarsson and Sæmundsson, 1987). Mapped faults and fissures are
also shown on some regional maps.
Earthquake graphs
The graphs show the timing and size of the earthquakes depicted in the map
above the graph. The same
colour-
coding applies to the graphs as to the maps (see
/earthquakes-and-volcanism/articles/nr/1225