Monday, December 6, 2021

Drunk on Geomorphology - Dead Horse Amber Ale


The next Drunk on Geology is for Dead Horse Amber Ale from the Moab Brewery in Moab, Utah. 

The first thing that sticks out about the beer is easily the name "Dead Horse", and although it is a grisly name, it is actually named after a geological feature nearby to the brewery, Dead Horse Point State Park, which is located outside of Moab near Canyonland National Park. The name of the park comes from a legend where cowboys would fence off wild mustang horses along the overlook, taking what horses they wanted and leaving the horses they didn't penned up to die of thirst. 

Above is an image taken from the overlook at Dead Horse Point State Park looking off towards the southeast. The river there is the Colorado River far below. Between us and the river lies 100 million years of geological history. From top (youngest) to bottom (oldest) the rock units go like this:

Entrada Formation: Jurassic (150 million years old) - This is a sandstone formed from a coastal dune environment. These are what the arches at Arches National Park are found in.

Navajo Sandstone: Jurassic (175 million years old) - Wind deposited, prehistoric "petrified" sand dunes from an ancient erg (sand sea), colored a light tan or white color. The units also preserve phenomenal cross bedding features from the sand dunes. These rocks form the majority of the rock formations in Zion National Park.

Kayenta Formation: Late Triassic (180 million years old) - A series of sandstones, shales, and limestones from a meandering river environment that frequently preserves dinosaur tracks. This formation is very well observed in the nearby Canyonlands National Park.

Wingate Sandstone: Triassic (200 million years old) - Like the Navajo, another wind deposited preserved series of sand dunes, however usually with more of a red tint to the rocks (rust). 

Chinle Formation: Triassic (210 million years old) - A stream deposited series of mudstone, sandstone, and conglomerates. Well known for containing uranium deposits, petrified wood, and fossils. You can see some of the ancient uranium mines in nearby Capitol Reef National Park.

Moenkopi Formation: Early Triassic (230 million years old) - A tidal flat deposited series of brown to red mudstones. The rocks will often feature ripple marks and raindrop imprints. You can see this formation especially well along the western entrance to Capitol Reef National Park.

Cutler Formation: Permian (250 million years old) - Comprised of sandstone and conglomerate, this formation was deposited along a coastal-marine beach with off-shore sands and non-marine alluvial floodplain deposits intermixed. The most notable feature of the Cutler is the White Rim Sandstone.

Honaker Trail Formation: Pennsylvanian to Permian (286-320) - Down at the level of the river lies this shallow sea deposit comprised of dark grey limestones with fossils. 

You'll note on the can though that is says "10 million years in the making" which is clearly not a reference to any of the rocks which are far older than 10 million years old. This is actually a reference to the location that this point is on, which is the Colorado Plateau. This region of the country has slowly been uplifted over the past 10 million years and the Colorado River at this overlook is a prime example of the effect of that uplift. 

Text on the side of the can:
"Dead Horse Ale is named after the scenic overlook near Arches National Park. A traditional English-style mild ale with a well balanced malt to hop ratio."
Around 10 million years ago the Farallon Plate, a large plate that was subducted below North America off the western coast of the the US, began to push upwards on the region. As the region was forced upward, the rivers that were formally allowed to meander naturally, started to erode downwards into the underlying bedrock. This downward erosion locked the rivers in place, creating a feature known as an entrenched meander. This entrenched meander is what created the "point" in Dead Horse Point, where an entrenched meander created the outcrop of rock jutting outwards.  

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