This week's Photo Friday is "Massive". This is the inside of the Valles caldera, a massive volcano in Jemez Mountians. What you may not be able to see in this picture is the large number of deer heards.

The Jemez mountains are a volcanic field in north central New Mexico that overlies the west edge of the Rio Grande rift. Volcanism began 13 million years ago. The most recent activity was 130,000 years ago. Magma ranging from basalt to rhyolite in composition has been erupted. The volcanic field is best known for the Valles caldera which formed 1.12 million years ago and produced the Bandelier Tuff. The Valles caldera is the most studied caldera in the United States (and probably the world). The geothermal and hot springs systems are caused by flow of groundwater through the caldera. The water flows near the top of a subsurface body of igneous rock that still may be partially molten (it is certainly still hot). Some of the water rises to the surface to supply fumaroles and hot springs. Geothermal activity continues. Based on the long history of the Jemez volcanic field and past cycles in activity it probably should be considered a dormant volcano that will probably erupt again.