Abstract
Distributed-style volcanism is an end member of terrestrial volcanism
that produces clusters of small volcanoes when isolated magma bodies
ascend from broad magma source regions. Volcano clusters can develop
over millions of years, one volcano at a time, and can be used to infer
unobserved geologic phenomena, including subsurface stresses and cracks
during eruption periods. The Tharsis Volcanic Province covers
approximately one-quarter of the martian surface and hosts a large
concentration of small volcanoes that formed from distributed volcanism.
We present a catalog of 1106 small volcanic vents identified within
Tharsis Volcanic Province. This catalog includes morphologic
measurements for each cataloged vent. Vent lengths range from 71 m to 51
km, widths range from 40 m to 3.1 km, and 90% of vents have lengths at
least 1.5 times their widths. Additionally, 90% of edifices associated
with vents have topographic prominences <100 m. Vents are
found throughout Tharsis, though they generally form clusters near large
volcanoes or among large graben sets. Older regions with volcanic
eruption ages of >1 Ga are found at the Tharsis periphery
in the Tempe-Mareotis region and Syria Planum. Vents in the Tharsis
interior have reported ages <500 Ma. Regional trends in vent
orientation and intervent alignment are dependent on nearby central
volcanoes and fossae. We use these findings to hypothesize that within
the most recent 500 Ma, magma was present under and to the east of the
Tharsis Montes and that some of this magma erupted and built hundreds of
small volcanoes in this region.