Who Does Hoodoos? EarthCache

This is an earth cache so there is no container to find. Please email the short but complete answers (through the CO profile) to the questions before logging this as a find. No need to wait for a reply from the CO before you log.

Just pull off along the side of the road, and you should have a decent view of this small sampling of hoodoos. Please be respectful of the area, any nearby foliage and wildlife, and always do CITO.

FTF: travelingsages, bellaannie!

If you own binoculars, bring them. These can be seen without binoculars but they would help. In the rainy season the stones may be obscured by vegetation. Just answer the best you can with what you can see. You will still get credit.

Stream and lake sand, basalts and silt deposits from the surrounding mountains fill the broad valley around Pinal Creek. These sediment materials, in some places over 1000 feet thick, fill the paces between angular rocks and boulders, some of which are over 20 feet in diameter. Geologists believe these deposits and formations are from the Pliocene and Pleistocene age.

At first glance you may not notice the several hoodoos here, snuggled on the hillside along with the rest of the landscape. These hoodoos here are evenly colored, a soft brown, with smooth sides, and wearing small rounded hats. They resemble a small group of people talking closely.

Hoodoos

Hoodoos are typically made of volcanic ash and other soft stone materials, and topped with a harder material. Over time, the softer materials are weathered away by rain and wind, and hoodoos are formed. Depending on the stone materials, the layers can vary in color and have irregular edges. Because of the way the stone erodes over time, the totem pole shaped structure often appears to be wearing a “hat” of the less erosive stone on top. Hoodoos have also been called a tent rock, fairy chimney, or earth pyramid.

The French call hoodoos demoiselles coiffées, which translates to “ladies with hairdos,” referring to the “hat” that hoodoos wear that their cousins, pinnacles, do not.

Ah-Shi-Sle-Pah sandstone hoodoos with their hats, New Mexico (Photo credit: https://upload.wikimedia.org/wikipedia/commons/2/25/Ah-Shi-Sle-Pah_WSA%2C_NM.jpg, by John Fowler from Placitas, NM, used by creative commons license.)

The name hoodoo came from early pioneers who, when they saw these rocks emerging from the mist, thought they looked like magical beings. The name refers to the use of energies in Hoo Doo, a form of pagan magic that came to prominence in the 1800s.

Hoodoos can be found on every continent, but nowhere else on earth are hoodoos more abundant than in Bryce Canyon National Park, in Utah.

Bryce Canyon Amphitheater hoodoos

(Photo by Jonathan Zander (Digon3), used under creative commons license from Wikimedia.)

Hoodoo Formation

(Public domain image, retrieved fromhttps://commons.wikimedia.org/wiki/File:Hoodoo_formation.jpg.)

Hoodoos typically form in areas where a thick layer of a relatively soft rock, such as mud stone, poorly cemented sandstone or tuff is covered by a thin layer of hard rock, such as well-cemented sandstone, limestone or basalt. The varied materials can reveal layers of colors along their mass. In glaciated mountainous valleys, the soft eroded material may be glacial till with the protective capstones being large boulders. Over time, cracks in the resistant layer allow the much softer rock beneath to be eroded and washed away. Hoodoos form where a small cap of the resistant layer remains, and protects a cone of the underlying softer layer from erosion. Further erosion of the soft layer causes the cap to be undercut, eventually falling off, and the remaining cone is then quickly eroded.

Rain is the chief source of the erosion that sculpts hoodoos. The summer monsoon rainstorms travel through the region, bringing short duration but high intensity rain. Rainwater is slightly acidic, which lets the weak carbonic acid slowly dissolve limestone grain by grain. It is this process that rounds the edges of hoodoos and gives them their lumpy and bulging profiles. Where internal mudstone and siltstone layers interrupt the limestone, you can expect the rock to be more resistant to the chemical weathering because of the comparative lack of limestone. Many of the more durable hoodoos are capped with a special kind of magnesium-rich limestone called dolomite. Dolomite, being fortified by the mineral magnesium, dissolves at a much slower rate, and consequently protects the weaker limestone underneath it.

Hoodoos in Arizona

Hoodoos in Arizona typically exist in high dry desert communities called “sky islands,” and were formed 35 to 25 million years ago. Geologists state these rocks are volcanic ash which fused into welded Rhyolite tuff (consolidated volcanic ash), with subsequent erosion creating the tall spires and columns. Sky island hoodoos are different from those in Bryce Canyon, which are limestone based and formed by frost wedging.

Coal Mine Canyon hoodoos (Photo credit: Taken by Doug Dolde, photo in public domain.)

There are a few hoodoos in the image above. Can you spot them? Some of these peaked stones were likely hoodoos at one time.

Hoodoos in Arizona can also be found in Petrified Forest National Park, Edmaiers Secret near Escalante National Monument, Coal Mine Canyon on the Navajo Reservation in northern Arizona, and in Ha Ho No Geh Canyon and Blue Canyon on the Hopi Indian Reservation of north Arizona. Now that you are more aware of them, you might be more likely to notice them along your geocaching travels.

Logging Requirements

Please email answers to these questions through messaging or CO profile. Short answers are fine.

1. Optional: Take your photo with the hoodoos behind you and post with your log.

2. Are the hoodoos around you formed from frost wedging or erosion of tuff made from volcanic eruptions? What is tuff?

3. Explain briefly why hoodoos often wear “hats.” How many hoodoos here are wearing hats?

4. Look at your feet and pick up a small rock. What is the difference between the rocks in the area and the hoodoos you see on the hillside? Mention texture and shape.