SFVF- SP Crater and friends

Hi,

This last week I went out with a local geologist on a field trip to visit SP Crater and its friends. Ken Walters was my guide on our adventure. I picked up some cool rocks that are good examples of tephra.

We drove north on Highway 89 past Wupatki, then turned left on a unmarked dirt road. We passed many Babbitt cows on our way to SP's neighboring cinder cone pictured below.

 This cinder cone* is older than SP because of all the vegetation covering its slopes. It is interesting to note the small cinder dome in the center of the volcano showing that even after the cone stopped spewing lava into the air, there was still activity. It also seems the the side of the cinder cone was blown out at some point as that side of the volcano is lower than the rest.

Looking at a map of the SFVF helps to visualize the location of these volcanoes. If you can see on the map, there is a fault labeled "Doney Park Fault." This fault can be easily seen from both SP Crater and the cinder cone discussed above.

Our nest adventure was up the side of SP Crater or **** Pot Crater because it looks a lot like a toliet.

Formidable right? Although only 800 feet high, it was a steep hike with loose cinders so you were constantly trying to not slid backwards. The volcano is about 71,000 years old. Below you can see some good examples of flow patterns. Apparently quarters are the standard tool for gauging size, but since I didn't have any I utilized a normal chapstick. Notice the curves and seeming rough texture. This was caused by the lava being squeezed out of the ground, much like the shape of frosting coming out of differing tubes. Also shown is the middle of the volcano. Like its neighbor, SP mostly erupted lava and rocks that fell back down around it, thus creating the cinder cone we see today.

SP mostly spewed out basalt, but towards the end of its life the magma burst through the bottom, creating a black lava flow across the ground. The lava flow was quite sharp and treacherous, but ion some places one could see how the lava fit together before it got weathered and broken apart.

Scientists are still unsure where the magma came from to cause the formation of these volcanoes, but there are two theories: 1) like Yellowstone, the SFVF is sliding over a "hot spot" in the mantle that has caused string of volcanoes seen starting out near Williams and stretching beyond Flagstaff onto the Navajo Reservation, or 2) a chunk of the lithosphere is sliding under a denser part of lithosphere and the rock is melting because it is coming into contact with warmer temperatures and higher pressure. Whatever the source is, we do not know where it is from or when it will reveal itself next...

Rachel signed out.

*The name of that cinder cone is Colton Crater.