The name “Mexican Hat” comes from a curiously sombrero-shaped, 60-foot wide by 12-foot thick, rock outcropping on the northeast edge of town. The “Hat”‘ has two rock climbing routes ascending it. It has frequently been noted on lists of unusual place names.
Steeply dipping strata define the western edge of the San Juan basin. To the west older geologic formations are exposed toward the Defiance uplift whereas basinward they are they are downwarped thousands of feet beneath younger rock units. Vast coal, uranium, oil and gas resources occur in the strata buried within the basin.
Elevation 5,050 feet.
See also: Little Cottonwood Rocks
Grove Karl Gilbert (1843-1918) is considered one of the greatest American geologists, having pioneered many theories in the earth sciences. In the late 1800s and early 1900s, Gilbert advanced concepts of mountain building, fault scarps, earthquake probabilities, and lake cycles that have withstood the test of time and are still used today. Furthermore, Gilbert applied science toward promoting public welfare by advocating the need for evaluation of risks and public disclosure of geologic hazards.
Utah was one of Gilbert’s favorite study areas where he formulated many of his theories. He spent much time at this particular location and was the first to establish that Little Cottonwood Canyon and Bells Canyon glaciers descended as far as the shoreline of ancient Lake Bonneville. Gilbert was also the first person to recognize the earthquake hazard posed by the Wasatch fault.
As you stand here look around, the magnificent cliffs, canyons, knobs, and spires before you are mostly cut from the 190 million-year-old Navajo Sandstone formation. Imagine the winds that carried sand to this area and deposited it in sand dunes hundreds of feet high. As wind shifted the massive sand dunes, the sands were deposited in a whirl of layers. Buried over eons of geologic time, the sands ceased their movement and turned to stone. Water releases the grains of sand from the grip of stone. Even here in an arid climate, water is the prime agent sculpting the stone into canyons, arches, and pinnacles. You are near the center of the great anticline that is the San Rafael Swell. Here, the layers are nearly flat-lying. It is like a stone dome with the curved top worn away. Soon the layers will begin tilting gently to the west.
The Wetumpka Impact Crater is the only confirmed meteorite crater in Alabama, United States. It is located east of downtown Wetumpka in Elmore County, Alabama. The crater is 7.6 km in diameter and its age is estimated to be about 83 million years (Cretaceous) old based on fossils found in the youngest disturbed deposits, which belong to the Mooreville Chalk. The crater is well preserved, including the original impact rim and breccia, but exposures are few owing to plant and soil cover, and nearly all are on private land. Thornton L. Neathery discovered the Wetumpka Crater in 1969-70 during regional geological mapping and published the first article on the subject in 1976. However, conclusive evidence of impact origin was lacking until 1998 when David T. King, Jr. and colleagues discovered shocked quartz in a core drilled near the center of the structure. In 2002, Christian Koeberl with the Institute of Geochemistry University of Vienna published evidence and established the site as an internationally recognized impact crater.
Each year, the city of Wetumpka sponsors annual ‘crater tours’ for the public in cooperation with local landowners and authorities. In March 2007, the Geological Society of America sponsored an international field forum for impact geologists led by David T. King, Jr. and Jens Ormö.
In May of 2007, Auburn University graduate student Reuben Johnson earned his master’s degree studying the impact crater. This work added to a growing body of evidence that Wetumpka’s crystalline “rim” may instead mark the edge of a deep central basin within what was originally a much larger impact crater that has since been almost completely eroded away.
700 Million years ago these blue to purple shales were deposited as silt and mud in shallow waters near the shore of an ancient sea.
Notice the pattern of mud cracks preserved on the purple rock.
After the layers were built up and compacted, they were tilted, and in time elevated to their present position by movement along the Wasatch fault.
To your left are layers of rock that have been folded and steeply tilted.
The light colored strata were deposited as sand and the dark as mud buried for eons of time the layers were subjected to heat pressure and earth movements which converted them to quartzites and shakes.
On the face of Storm Mountain 2000 feet above your right shoulder you see sparse vegetation die to resistance of the quartzites to weathering.
Slip & Slide – Landslides
Over the years, the slide area above you has been very problematic, in 1986, a landslide moved the pipeline. The slide eventually covered and crushed the pipeline.
Because of the active nature of the slide, the pipeline was eventually moved from the hillside, and the water now flows through a tunnel undernearh the active landslide.
See Also: G.K. Gilbert Geologic View Park
Little Cottonwood Rocks
Geology and History of Little Cottonwood Canyon
Little Cottonwood Bedrock
Three Bedrock units are visible on the north side of, and in Little Cottonwood Canyon :
- Little Willow Formation
The little willow formation is approximately 1.7 billion years old, making it the oldest rock in the Salt Lake City area. The highly metamorphosed rock consists primarily of intensely contorted quartz schist and gneiss intruded by igneous rocks that have been altered to amphibolite and chlorite schist.
Big Cottonwood Formation
One billion to 850 million years old, the Big Cottonwood Formation is a low-grade metamorphic rock that consists of reddish-brown quartzite and black to purple to green shale, argilite, and slate. Originally deposited along the shoreline of an ancient sea, ripple marks and mud cracks are still preserved in this rock.
The rock on the north canyon wall is easy to distinguish from the adjacent light gray “granite” father up the canyon.
Little Cottonwood Stock
This igneous rock is quartz monzonite, or more generally called granite. Between 32 and 31 million years ago, magma pushed up through the crust into overlying rock layers and then cooled and solidified before reaching the surface. Quartz monzonite is composed of plagioclase, quartz, orthoclase, biotite, and hornblende.
Popular for rock climbing, this light grey granite rock makes up most of the canyon walls.
A history of the rocks in this area :