Large Cones
Mars has a number of volcanoes with diameters between 50 and 150 km. These
volcanoes are thus the same size as many large Earth volcanoes. Most are
found within the Tharsis and Elysium regions. However, they are all older
than the giant shield volcanoes. Thus, many have been partly buried by
younger lavas. These volcanoes are divided into two general types. The
first type are called "paterae," after the Greek word for a shallow saucer
or bowl. They are fairly flat, they generally have little relief, and they
often have large calderas. The second class of volcanoes are called
"tholi." These volcanoes have much steeper sides, and they typically are
taller than the patera structures. Both types apparently formed mostly
from basaltic lava flows. Thus, they are much like Earth shield volcanoes.
Their different appearances may mark either different depths of burial or
changes in the nature of volcanism.
Biblis Patera
Ceraunius Patera
Jovis Tholus
Ulysses Patera
Uranius Tholus