Tag Archives: Geology
Built of Stone
About 237 million years ago theMoenkopi Formation rocks were deposited in a coastal plain that covered what is now northern Arizona and surrounding states. The plain ended at the shoreline of a sea in Utah. Seasonal stream beds crossing that plain deposited thick sheets of sand. Over millions of years, “another 10,000 feet of Mesozoic sedimentary rocks accumulated.”
All of these sedimentary layers have been warped, twisted and eroded, ending up being uplifted by molten lava between 70 million and 30 million years ago as a huge chunk of thick crust. This was the origin of the Colorado Plateau, a 130000 square-mile block. In time, that molten base began to erupt in the San Francisco volcanic field, creating thousands of cinder cones, long lava flows, the stratovolcano known as San Francisco Mountain, and lava domes like Mount Elden near present day Flagstaff. Volcanic activity continued, with the most recent eruption occurring in AD 1064. At that time, the Sinaguan people found that the loose cinders made a good mulch for growing crops, and they created Wupatki. They used the red Moenkopi sandstone exposed in the area along with Kaibab limestone and black basalt from the volcanic field to build substantial buildings.
Centuries later, when the railroads necessitated the creation of the town of Flagstaff, the buildings were made of wood. However, over the years the citizens learned the same lesson that many cities of the day learned, as fires consumed the town. When reconstructed, the materials of choice were identical to those of the ancients, Moenkopi sandstone, Kaibab Formation limestone and volcanic basalt.
Used copies of the Stone Landmarks are available for purchase at various booksellers. Photos are my own.
Prospectors and investors moved into Arizona after the Gadsden Purchase of 1853. To obtain the silver and gold they hunted, miners dug into the sides of hills and into shafts dug down into the earth. Boom towns like Tombstone called to talented hard-rock miners world-wide, who came to Arizona to find work and a future underground.
My father, my grandfather and my great-grandfather all worked underground in the mines of Bisbee, Arizona. I grew up listening to tales of the dangers and excitement of the mines. The near-misses, the rescues, the mammoth roaches and the temperatures. Two thousand miles of underground tunnels hollow the earth beneath Bisbee and the surrounding countryside. Sometimes Dad worked the night shift and we would go pick him up after work still in the dark. The daily afternoon blast siren was a normal occurrence. Every Bisbee child was well-versed in blasting cap safety.
I recently taught several groups of first graders a bit about Arizona geology, and was surprised to realize how little students today know about mining. “Who can tell me what a mine is?” I asked. The quick response was, “like Mine-Craft?” I realized it will be a large task, helping Arizona’s future know about Arizona’s past.
Please take time to enjoy this terrific video presented by the City of Bisbee, the Bisbee Mining and Historical Museum and the Bisbee Queen Mine Tour. Watch the video here.
Underground miners were certainly aware of the monetary value of the silver, gold and copper that they mined, but they also were awed by the beautiful caverns formed deep underground and covered with the secondary forms of the ore they blasted, shoveled and hauled up from the mines. These often take the form of delicate crystals with wonderful colors. As a child I was lucky to visit one such crystalline cave. In 1997 the Smithsonian Museum in Washington recreated one of these Bisbee caverns in the Museum. I keep a copy of the book commemorating it in my rock case, Treasures of the Queen by Richard Graeme.
T is for Texas Canyon, Tombstone and The Thing
If you drive a car on I10 in southern Arizona, you will undoubtedly see sign after sign asking “The Thing?” In fact, a miracle in advertising, the first signs begin near El Paso, TX, traveling west. By the time you arrive at exit 322, in the middle of the desert between Willcox and Benson, Arizona, your curiosity should be aroused. For a whole dollar, you can find out just what The Thing, the Mystery in the Desert, is. And you can buy an ice cream cone, or other tourist delights.
In the same southeastern corner of the state you will encounter beautiful Texas Canyon, rich in the history of Arizona Territory, the Butterfield Stage Route, ranching, and Apache country.
A few minutes driving will take you to famous Tombstone, Arizona. In 1877 Ed Schieffelin announced to cavalry stationed in Fort Huachuca, Arizona, that he intended prospecting in the valley of the San Pedro River. He was warned that he would only “find his tombstone there.” It was a dangerous time in Arizona Territory because this was Apache country. But he persisted, found silver and staked the Tombstone and Graveyard claims. Soon other rich deposits were discovered and more prospectors came and the town of Tombstone blossomed. It was a rough, tough boomtown until 1886 when fire destroyed the pump works and the mines flooded. Tombstone remains as a thriving tourist attraction, complete with shootouts in the streets, busy saloons, stagecoaches and people dressed in the best of western wear.
Q is for Quartz
Quartz is the most common mineral of all. It is a form of silica. You can find Quartz that is transparent, or milky or translucent. There are also more varieties of Quartz than any other mineral. Some of the varieties are familiar names, such as Amethyst, Citrine and Agate. Rock collectors enjoy the hexagonal crystals which can be quite large.
Clusters of tiny crystals are known as “drusy quartz.” The most commonly seen chunks of quartz in Arizona are milky white and massive (not crystalline), also known as “bull quartz.”
Arizona prospectors have long looked to Quartz as a possible sign of gold. Some Quartz veins may have gold filling the fractures in the Quartz. Sometimes gold is hidden in pockets of sulfide minerals such as pyrite in the Quartz. Gold panners sift through sand, which contains lots of Quartz, to sort out the heavy bits of gold from the debris.
Grand…Grand Canyon, of course
Welcome to My Arizona
I was born and raised in Arizona and have lived here almost all my life. My only goal in keeping this blog is to share with you some amazing things about this state from my perspective. I have many areas of interest and will cover everything from Aurichalcite to Ziziphus obtusifolia. Lots of photographs will be included as I am an unapologetic snapper of pictures and feel that truly a picture is worth a thousand words or so. Arizona is a place of interest for scientists and tourists and residents. The geology lies exposed for all to see and study the forces that have created the mountains and canyons. Because of the great range of elevations, a great variety of plants and animals are found here. Studies in the 1890s led to the establishment of 6 different life zones. These zones describe the differences between the desert land that Arizona is famous for, and also the high plateaus and pine-covered mountain peaks that may surprise visitors. Human history has left a deep footprint in the state and the stories told give us a dusty window into the wild west.
I invite you to come along if you think it all might sound interesting. Follow me on Twitter as Fan of Arizona, @fanofnmtn.