Inflated Lava Flows on Earth and Mars

Post by Dr. W. Brent Garry1, Dr. Jacob E. Bleacher2, Dr. James R. Zimbelman3, and Dr. Larry S. Crumpler4

  1. Planetary Science Institute, Tucson, AZ, 85719, USA
  2. Planetary Geodynamics Laboratory, Code 698, NASA Goddard Space Flight Center, Greenbelt, MD, 20771, USA
  3. Center for Earth and Planetary Studies, Smithsonian Institution, National Air and Space Museum, Washington, DC, 20013, USA
  4. New Mexico Museum of Natural History and Science, Albuquerque, NM, 87104, USA

In volcanology, we are traditionally taught about basaltic lava flows advancing as toes of pāhoehoe or as channeled ‘a‘ā flows.  However, under the right emplacement conditions, some basaltic sheet flows will inflate (thicken) from only a few centimeters or meters to almost 20 meters in height.  This process occurs when lateral advancement of the flow is inhibited and liquid lava is injected underneath the solid crust of stalled sections of the flow field, causing the crust to uplift over an expanding liquid core.  The study of inflated lava flows on Earth reveals distinctive morphologic features related to this process including tumuli, inflated sheet lobes (Image 1), squeeze ups, and inflation-rise pits [1,2].  The McCartys lava flow (Image 2) is a 48-km-long, basaltic lava flow in El Malpais National Monument, near Grants, New Mexico that exhibits many of the complex morphologic features related to the process of lava flow inflation.  By studying the morphologic features that are characteristic of inflated lava flows on Earth, we can begin to identify this style of lava flow on other planetary bodies, including the Moon and Mars [3,4,5].

Image 1

Image 1. Geologist Dr. Jake Bleacher stands on the edge of a 12 meter high inflated sheet lobe in the McCartys lava flow, New Mexico. This inflated lobe continues in the foreground and extends in the distance along the left side of the photograph. Cracks, up to 8 meters deep, have formed along the margin of the lobe as the brittle crust had to accommodate for the inflation. The lower elevation unit seen in the central part of this photograph is formed from breakouts along the margin of this inflated sheet lobe and has a hummocky and swale surface texture. Photograph by W. Brent Garry. Full Size Image.

Image 2

Image 2. Inflated sheet lobes expand for 100s of meters, as seen in this remote sensing image of the southeast portion of the McCartys lava flow, parking lot for the Lava Falls trail. The arrow points to the location and direction of view for the panorama in Image 1. Inflation-rise pits can be scattered throughout the inflated sheet lobes. The margins of the flow are comprised of a complex sequence of breakouts. Image credit: Google Earth.

Image 3

Image 3. On Mars, we are discovering lava flows that have similar characteristics to terrestrial inflated lava flows. Here, the distal end of a 42-km-long lava flow (upper left of the image) near Pavonis Mons, embays the base of a low-shield (lower-right in the image). The lava flow exhibits broad platforms, terraced margins, and depressions within the flow interior. THEMIS Image V19126002. Image credit: NASA/JPL/ASU.

For perspectives from the field, explore GigaPans of the McCartys lava flow to see the dramatic morphology of inflated lava flows.

  1. 360° Panoramic view of the McCartys lava flow from the field: http://www.gigapan.org/gigapans/74044/
  2. A view from on top of an inflated sheet lobe on the McCartys lava flow:

http://www.gigapan.org/gigapans/74347/

  1. A breakout of lava from an inflated sheet lobe on the McCartys lava flow: http://www.gigapan.org/gigapans/74336/
  2. Another view from the top of an inflated sheet lobe on the McCartys lava flow:

http://www.gigapan.org/gigapans/74341/

Further Reading

  1. Walker, G. P. L. (1991), Structure, and origin by injection of lava under surface crust, of tumuli, “lava rises”, “lava-rise pits”, and “lava-inflation clefts” in Hawaii, Bull. Volcanol., 53(7), 546-558.
  2. Hon, K., J. Kauahikaua, R. Denlinger, and K. Mackay (1994), Emplacement and inflation of pahoehoe sheet flows: Observations and measurements of active lava flows on Kilauea Volcano, Hawaii, Geological Society of America Bull., 106 (3), 351-370.  
  3. Garry, W. B., J. R. Zimbelman, and J. E. Bleacher (2008), Morphology and emplacement processes at the distal end of the Carrizozo lava flow, New Mexico: Implications for Martian sheet flows, Lunar Planet. Sci., XXXIX, Abstract 1734.  
  4. Zimbelman, J. R., W. B. Garry, J. E. Bleacher, and L. S. Crumpler (2011), Inflation features on the distal pahoehoe portion of the 1859 Mauna Loa flow, Hawaii: Implications for evaluating planetary lava flows, Lunar Planet. Sci., 42nd, Abstract 2443.

5.      Garry, W. B., J. R. Zimbelman, J. E. Bleacher, S. E. Braden, L. S. Crumpler, and the LROC Team (2011), Lava flow inflation features on the Moon?: A comparison of Ina with terrestrial analogs, , Lunar Planet. Sci., 42nd, Abstract 2605.

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