Saguaro National Park

When I finally reached Tucson I quickly found a site at the Gilbert Ray Campground and then bee lined it to Saguaro National Park (West). I knew there would be a geology talk in about a half an hour and I wanted to get there on time.

The park volunteer gave a good talk but I couldn’t possibly write it all up here. I am beginning to better understand the geology of this area and geology in general. The park is in a very large caldera, which is a cauldron-like volcanic feature created by the collapse of land following a volcanic eruption. It is a from the Spanish word that originated from the Latin “Caldaria” or “cooking pot”. About 70 million years ago a large volcano formed and then collapsed, next the tectonic plates moved and stretched this region to look much like it does today. I was constantly encircled by mountains.

Here is a view from the back of the Visitor Center where you can see the iron red rocks.

Many of the national parks are named after geological features but this one is named after a plant, Saguaro Cactus (Carnegiea gigantean) to be exact. Exclusive to the Sonoran Desert, it is the size of a tree and surprisingly long lived, up to 200 years.

They don’t even develop side arms until they are 75 years old and up until that time they are called spears. Its success is due to its ability to adapt to the harsh conditions of the desert with little water and extreme heat. A single tap root about 3 feet long with smaller roots 4-6 inched deep radiating out as far from the cactus as it is tall.

The main characteristic is the spines which are actually modified leaves. They not only protect the plant from nibbling but actually provide some shade which help prevent water loss caused by the dry winds. You can see them below along with a Gilded Flicker

The Flicker then flew to a nearby hole and climbed in for the night.

Here is a diagram from the visitor center showing what it looks like inside.

The pleats of a Saguaro allow the plant to expand while it is absorbing rainwater, and to shrink when using its stores of water. I think I could personally use some pleats on my body.

Cacti make their food through a process called photosynthesis like most plants but with a slight difference. It is a technical explanation but the bottom line is that they only open their pores at night to conserve water and the water is very acidic. The idea that cowboys cut open saguaros for water to drink doesn’t hold true, it would have been yucky to say the least.

When you watch western movies, particularly old ones with John Wayne riding through Saguaro covered hills you can be sure it was filmed in this area, probably at Old Tucson, just down the road. When kids draw cactus they draw saguaros probably because that is what they have seen in the movies.

The visitor center has a lot of good information about the area and the saguaros.

Below is a close up of the nuts.

This unusual young saguaro is just beginning to form a crest, which may eventually grow to more than six feet wide.  The literature said, "A crest can develop when the growing point, or meristem (which produces new stems and spines or leaves), elongates into a line." Evenutally it may become convuluted and resemble a brain. Aparently this phenomenon has been seen in most plant species and they are not sure of the cause. Personally I think it is pretty cool looking.

The sun was beginning to set so I packed it in for the day.

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