12 - 18, EEAS Professors Lori Weeden and Kate Swanger took seven students on a
whirlwind tour of southwestern geology. To
bring you this report on the geologic history of Utah and Arizona, these nine
brave souls had to endure ridiculously picturesque scenery, excessive laughter
on long van rides, and delicious s?mores cooked over the campfire. It was a
most perilous expedition.
Zion National Park, southwestern
At our first
stop we marveled at the 2,000-ft high cliffs of Navajo Sandstone in Zion NP. These
rust-colored sandstones were deposited during the Jurassic, when stegosaurs and
brachiosaurs roamed our continent, and Utah was buried under a massive expanse
of sand dunes. All of the continents had come together to form one
supercontinent, Pangaea, and the colossal Appalachian Mountains (still young
and as tall as the present-day Rockies), were shielding the western US from
rain, causing a vast desert to form in Utah.
NP the students braved steep cliffs to hike the famous Angel?s Landing Trail.
On this hike, we got a close-up view of the large-scale cross-beds of the
Navajo Sandstone, formed as sand dunes migrated and buried each other. We could also clearly see the gradation of
brown to pink to white in the Navajo, which is caused by variations in the
oxide minerals that cement this impressive deposit.
Left: Zion National Park, southern Utah. Right: Cameron Simmons poses next to chevron folds in Kolob Canyon, Zion National Park.
Bryce National Park, southwestern
the break-up of Pangaea, 200 million years ago, North America was inundated by
a massive inland sea that covered much of the interior of our country,
including Utah. In this warm, lush environment, dinosaurs still ruled North
America. But ?all good things must come to an end.? By the time the Yucatan
Peninsula was hit by an asteroid 65 million years ago (marking the end of the
dinosaurs), the waters were already retreating from the interior of the US. The
Rocky Mountains were beginning to rise, and along with them the Colorado
Plateau where Bryce NP and Grand Canyon NP now reside. From 70?40 million years ago, as Utah
emerged from the ocean, vast fluvial and lake deposits were formed, including the
sandstones, siltstones and limestones that would eventually form the famous
?hoodoos? of Bryce NP. These hoodoos (or
spires) formed during the past few million years, as wind and water eroded vertical
fractures in the rocks, making Bryce NP one of the most unique and gorgeous
landscapes on Earth.
Left: Alison O'Connor and Dylan Cole hike through Bryce Canyon National Park, southern Utah. Right: Ryan Farrell investigates the Claron Formation limestones in Bryce Canyon National park.
Grand Canyon, northern Arizona
by the mighty Colorado River during the past six million years, the Grand
Canyon has beckoned tourists, adventurers, and artists from around the globe. It
stands as a clear testimony of the power and antiquity of the Earth we live on,
reminding us that we are but tiny pieces in a greater whole that has existed
for billions of years and that will continue to exist long after we are gone.
first glimpse into the Grand Canyon came after a long van ride, when we stopped
along the eastern South Rim. Though exhausted, we were enraptured by its
beautiful enormity and couldn?t wait to hike down Bright Angel Trail the following
day. Along with pack-mules, horses and hundreds of other travellers, we
literally hiked backward through time, starting with the 270-million year old Kaibab
Limestone that caps the South Rim, down to the 505-million year old Muav
Limestone. Had we more time and
endurance, we could have hiked all of the way down to the Vishnu Schist, a 1.7-billion
year old rock that forms the ?basement? of the southwest. Every year, thousands
of hikers take this journey, hiking ?rim to rim,? traversing 1.5 billion years
of earth history in less than a day.
left to right: Rachael Megnia, Kate Swanger, Cameron Simmons, Tara Cenzalli,
Ryan Farrell, Lori Weeden, Sephera Simoneau, Alison O’Connor, and Dylan Cole on
the South Rim of the Grand Canyon, northern Arizona.