Sandia Crest and Albuquerque Volcanoes

Monday 29th May 2006

Sandia Mountain

The first stop takes place in Sandia Mountain on the East side of the Rio Grande rift. Its name comes from the color of granite (red) and trees at the top (green) during the sunset. The summit culminates at about 3200m.

Picture 1 : The Great Unconformity on Sandia mountain

Most of the mountain is formed by a Precambrian granite. We can see at the top of it, some Mississippian carbonaceous sediment deposits (carboniferous). This is the Great Unconformity. We can follow it on the landscape along the mountain when you drive to the South.

Picture 2: All together…

Albuquerque Volcanoes

During the second stop, we saw 3 volcanic cones: they measure about 20 meters high, and are lined up according to a North South axis, in line with Jemez Mountains.

They appeared 156000 years ago, and form hawaiian pahoehoe lava flow: it is a very dark basaltic lava with vesicles which show the way of the lava flow. We can see inside many little feldspath and olivine minerals.

Moreover we find pyroclastic breccias with spindle-shaped bombs.

The three cones are located on faults, and there’s an uprising of the mantle underneath, observed by different geophysical methods.

Picture n°3: Picture taken on the top of the southern spatter cone (Yara and Manue give the scale…)

Picture n°4: The northern spatter cone Picture n°5: Diagram of Hawaiian-style eruptive activity (1)

icture

Picture n°6: The three spatter cones and their relation with the morphology of the landscape

(1) Gary A. Smith and al. , Basaltic near-vent facies of Vulcan Cone, Albuquerque Volcanoes, New Mexico, in New Mexico Geological Society Guidebook, 50^th Field Conference, Albuquerque Geology, 1999.