How Are Lava Plains Identified?
Another sign indicating the volcanic origin of a plain is the existence
of volcanic cones on the plain (Figure 6.17). In the middle of this image,
there is a cone about 4 km across with an elongated caldera.
Small cones with a summit pit can also be found on other lava
plains (Figure 6.18) . Most of the cones in this photo are about
500 m (or 1/3 mile) across. Their linear alignment may be
related to the fault system of the area. Exactly how they formed
is not known. Viscosity of the lava might also play a role in their
Contrasts of surface smoothness can be diagnostic also (Figure
6.19) . Some experience may be required to delineate the origin
of different smooth surfaces. The existence of wrinkle ridges may
also be indicative because it takes a harder surface (such as the
ones formed by lava flows) to buckle to produce wrinkle ridges (Figure