What you are looking at is one of the most
spectacular geologic formations in Arizona, that only a select lucky few have been able
to visit. Known as "The Wave", it showcases hundreds
of feet thick of layered and variable colored sandstone rock units that formed when the
area was part of the vast Pangaea supercontinent more than 190 million years ago, and the local
area was far dryer and hotter than it is today, allowing for unusually hot summer days to
reach a temperature of up to 135 degrees Fahrenheit. Today, due to how fragile this rock formation
is, for many years only up to 16 people were allowed to visit it each day, with people
being chosen at random via a lottery system out of more than 200,000 that applied to visit
in 2018 alone. This number has now increased to allow for
up to 16 groups or 64 people a day as of 2021, whichever comes first but still the vast majority
of people who apply are still left out. Regardless, how did this fascinating rock
formation form, and what story does it tell? The Wave rock formation can be found on the
very northern section of Arizona where it is 1800 feet from the Utah border, being 31
miles west-northwest of the city of Page. From satellite, you can see the numerous bands
of the primary rock unit which composes this formation, being known as the Navajo Sandstone. Although The Wave is seemingly overlaid with
a patch of white rock that has a cauliflower like appearance, this is once again all the
same rock unit. The Navajo Sandstone largely formed between
200 and 195 million years ago during the very beginning of the Jurassic period when 90%
of the world's landmass was locked up as the supercontinent Pangaea. In what would eventually become Arizona, mountain
ranges that had formed several hundred miles to the west for millions of years prior had
absorbed incoming moisture from the ocean, thus leaving only minimal precipitation to
fall on an area that was a vast desert. This desert was closer to the equator than
modern day Arizona, sharing a climate typical of northern Mali or far southern Algeria. There, wind was the dominant erosional force,
pulverizing large quantities of existing rock into smaller and smaller grains until sand
particles were formed. Sand for context describes an array of rock
particles where the majority are between 2 millimeters and 1/16th of a millimeter in
diameter. After millions of years of a hot desert climate,
the largest known sand dune field in Earth's geologic history formed, even being more than
33% larger than the modern Saharan Desert dunefields. These sand dunes covered an area of 800,000
square miles, encompassing a vast desert spanning from New Mexico to Wyoming. Hundreds and in some cases thousands of feet
of sand piled up, and in these vast sand dunes blown by wind The Wave began to form. You might note that rocks in The Wave appear
tilted almost like they have been uplifted. However, this is not the case as the rocks
are not actually tilted but rather represent a type of rock formation known as cross bedding. As wind blowed across the ancient desert landscape
with a few dinosaurs present, it caused frequent small scale landslides to occur as sand slumped
across the top of a dune and rolled downslope, moving in the direction the wind was blowing
towards. Over time, the assortment of grains this process
moved resulted in many layers of cross bedded rock units. As for the sudden breaks and changes in tilt
within some layers, this is because they represented multiple layers of sand dunes which moved
across the desert, and sometimes the wind direction changed. Due to erosion of overlying rock and the uplift
of the Colorado Plateau, the Navajo Sandstone became once again exposed on the surface,
where rainfall began carving into the rock units. This formed numerous small and large scale
ravines and valleys which cut through the Navajo Sandstone, revealing their numerous
layers, with this forming their modern appearance. Thanks for watching! If you would like to request a specific topic,
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