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University of Missouri Department of Geological Sciences

Rock type:      Basalt
Location:        near Grants, NM

This rock is from the toe of the McCartys lava flow, which formed only about 3,000 years ago. The

lava erupted from a small cinder cone (only about 25 feet high) but the hot fluid basaltic lava

traveled 38 miles (~60 km) to the north. Interstate 40 crosses the end of the flow, and this sample

came from exit 89. Most of the flow is within El Malpais National Monument, where it forms giant

lava tubes and flows with spectacular ropey textures, often called pahoehoe, which is the

Hawaiian word for this kind of lava. 

Photo by Alan Whittington, MU Geology

Resources:

New Mexico Bureau of Geology and Mineral Resources web guide to pahoehoe

features of the McCartys lava flow:
http://geoinfo.nmt.edu/tour/federal/monuments/el_malpais/zuni-bandera/pahoehoe.html
National Parks Service webpage for El Malpais National Monument:
http://www.nps.gov/elma/index.htm 

MU Geology Department
http://geology.missouri.edu/