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Basaltic Lava Flow
April Carty

Physical Geology
Spring 2009

                                                  Carrizozo Malpais Lava Field, New Mexico
                               Valley of Fire in the Land of Enchantment

Picture by oxman386's
 

            New Mexico is most famous for Los Alamos where they worked on the atomic bomb, and also for White Sands Missile Range where the White Sands National Monument is located.  If one were to drive late at night near Roswell, New Mexico, one might see UFO’s. If you’re in Lincoln County you might see Billy the Kid in the Lincoln County Wars.  But there is another place in New Mexico most people never get to see, and it is just as amazing as all these other places- the Valley of Fire Recreation Area.  It is off from the main roads that most people travel, and down a road that winds its way through the desert on its way to Carrizozo.  One minute you see the desert landscape and suddenly the desert disappears, and you are looking at a Basaltic Lava Flow from long ago. 
 

Three miles northwest of Carrizozo, New Mexico at the elevation of 5,250 feet, there is a 430-acre tract of land adjoining US—380 which became the Valley of Fire Recreation Area on May 6, 1966.  The park encompasses a large portion of black fissured lava of the Carrizozo Malpais.  

 

100_0367 by oxman386.

Picture by oxman386's
 

The Lava Flow is called the Malpais (which roughly translates “bad footing”) Lava Flow, and it originated from the Little Black Peak which filled the Tularosa Basin with hot molten rock.  Little Black Peak is a very small cinder cone, it is only 27 meters tall, and appears surprisingly small to have produced the entire 4.3 cubic kilometers of lava which formed the Carrizozo Malpais Lava Field.  The Malpais Lava Field formed much the same way that a Hawaiian-style volcano does. 
 

In Hawaii today this type of eruption is very passive and is typically characterized by lava pouring out from a small vent and then travelling either across the earth’s surface or through lava tubes until it cools and solidifies.  Geologists estimate that the entire Carrizozo eruption would have taken 2 to 3 decades, and that the eruption would have proceeded at a slow and steady rate.  The lava covered ground makes it nearly impossible for animals to walk on.  But plant life is still able to grow on this lava covered ground. 
 

100_0369 by oxman386.

Picture by oxman386's

 

The Lava Flow is four to six miles wide, 160 feet thick, and covers 125 square miles.  It is considered one of the youngest lava flows in the continental United States.  The lava flow of the Carrizozo area is from two basaltic flows which erupted from within the Tularosa Basin. 
 

The Carrizozo Lava Flow has many preserved features which are being observed in currently-forming Hawaiian-style Lava Flows.  The lava is characterized by pahoehoe textures such as ropey flows, as well as, smooth lava sheets, toes, tumuli, and pressure ridges.
 

http://geoinfo.nmt.edu/tour/landmarks/carrizozo/images/pahoehoe-sm.jpg 

Picture by New Mexico Bureau of geology and mineral Resources
 

(Pahoehoe such as these in the picture above forms when the surface of the flowing lava begins to cool and the underlying, hotter lava is still flowing, and then the cooler surfaces are dragged along by the flowing lava underneath and so forms the wrinkles).

Collapse area

Picture by New Mexico Bureau of geology and mineral Resources

Collapse area

fissure

Picture by New Mexico Bureau of geology and mineral Resources
Fissured top of ropey flow
 

Tumulus 

Picture by New Mexico Bureau of geology and mineral Resources

Tumulus with longitudinal fissure
 

collapsed pit

Picture by New Mexico Bureau of geology and mineral Resources

Squeezed-up lava and collapsed pit (probably into lava tube)
 

            The top flow of lava is well preserved, and in some places even retains an iridescent appearance that is typical of young lava flows.  The age of the lava flows are roughly around 5,000 years of age.  The Malpais Lava Flow is actually two lava flows which erupted at nearly the same time, and probably from the same vent.  The shape and extent of the two flows are the Carrizozo field.  One type has the lower flow extending for a full 75km length, and the central part of the flow is narrow whereas the lower part spreads to a width of nearly 8km.


          The second type is the upper part of the lava flow which extends approximately 25km from the vent, is wider on average than the lower flow, and where both flows can be observed is typically thicker.  Also the contact between the upper and lower flows is brecciated, and there is no evidence of erosion or soil development which suggests that the time between eruptions of the two flows was relatively short. 
 

The lava of the Malpais Basalt is alkaline to transitional olivine basalt, the rock is typically unaltered, and the lava is transitional between hypersthenes and nepheline-normative which is mostly likely to be derived from mantle, and is enriched incompatible elements or has undergone some crustal contamination.   The basaltic lava flow also contains phenocrysts of olivine, plagioclase, pyroxene, the green olivine is 1mm, and the groundmass of lava is composed of plagioclase, olivine, augite, glass, magnetite and ilmenite.
 

100_0364 by oxman386.

Picture by oxman386's
 

In conclusion, it always pays to get off the main roads, and go down paths that few travel, because one never knows what one will find.  For instance, tucked away in the surrounding desert terrain is a lava field just waiting for one to come and take a look at it.  

100_0368 by oxman386.

Picture by oxman386's

 

 

Work Cited
http://www.americansouthwest.net/new_mexico/valley_of_fires/recreation_area.html

http://www.agmc.info/valley_of_fires.htm

http://www.blm.gov/nm/st/en/prog/recreation/roswell/valley_of_fires.html

http://www.flickr.com/photos/texasj/682289911/

http://geoinfo.nmt.edu/tour/landmarks/carrizozo/home.html

http://www.geo.utep.edu/loca/Volcanos/VALLEY.HTML

http://en.wikipedia.org/wiki/Carrizozo_Malpais