The Ives flow, a little bit of Hawaii
Flujo de Ives is unique within Pinacate; its volume is an order of magnitude larger than any other volcano, it is a tholeiite in a field of alkali olivine basalts, and its surface is almost entirely pahoehoe with a few areas broken into aa. Ives built an enigmatic pyroclastic cone within one major vent but otherwise produced meager spatter ramparts as copious low viscosity magma poured from a set of fissures. Other monogenetic fields have similar pahoehoe flows.
The source vents are near the base of Santa Clara where the pre-Ives surface elevation is around 200 m. Ives flowed south toward the Sierra Blanca and split into two branches; one went east and its distal end is 7 km from the Terror pit crater at 90 m elevation. The other went south, stopping 13 km from Terror at 60 m elevation - a gradient for both of about 1%. Ives flowed around and nearly buried some outlying peaks of crystalline rock northwest of Sierra Blanca that now project as inselbergs above the surface.
Ives is named for Ronald L. Ives, first scientist to systematically study Pinacate in detail.
Ives looks different in overview from all the other flows. Sand blown east from the adjacent Gran Desierto has “ponded” in the low areas between the billows and tumuli giving it a mottled appearance as seen from above. No other flow is like it. The open nature of rougher lavas swallows sand and that kind of lava flow has to fill from the bottom before sand can be important on the surface.
Ives north to south is 15 km, east to west 10 km. The source on the north is at 220 m elevation and the distal end on the south is at 60 m, a gradient of about 1%. Lava flowed down hill toward the end of the Sierra Blanca and split; a minor amount flowed east and the largest volume flowed south around the crystalline rock. Some peaks of the Sierra Blanca northwest of the main mass were surrounded by the lava and now project as inselbergs through the basalt, others are probably buried.
This gallery of images shows a long view of the flow. Microsoft/Yahoo Flashearth is an alternative to Google Earth whose coverage of Ives has poor resolution.
Ives came out of a 3.3 km-long set of parallel N-S fissures that opened near the south base of Santa Clara. Four or five minor fissures opened on the north and gas activity built spatter ramparts around their discontinuous vents. This is the only visible pyroclastic material on the flow. The most productive fissure is marked by two prominent pit craters. This fissure was probably open for most of its length during most of the eruption, feeding sub-surface lava tubes and creating only these surface features.
The two prominent pit craters seen in the image from the Camp Cone are probably on the main fissure source of the magma. Juan Matteo Manje, involved in the Kino explorations around 1700, described chasms of "terror y espanto" (terror and fear) in his diary and the best interpretation of his writing suggests these pits are what he saw so I have used his names.
Terror, the larger, is surrounded by an apron of "shelly pahoehoe" (link) thin sheets of basalt dangerous as hell. indications of low viscosity, high gas content