Lab/field assignment geology

1. Geology of Red Rock Canyon
and surrounding areas
Bodie Whalen

2. Southern California/Western Mojave Desert
Location: The Mojave Desert is a region of over 15,000 square
miles consisting of flat valleys and low-lying hills.
Formation: The Mojave was once part of an ancient interior sea;
the desert was created not only by volcanic activity consisting of
lava surfaces and cinder cones, but also by deposits from the
Colorado river (Jaeger). Most of the geologic history there took
place during the Mesozoic and Cenozoic eras of time.

3. Continued
Forces of erosion: There are strong, dry winds blowing all
year and an annual rainfall of 5in which mostly takes place
during the Winter.
Protected land: Almost 1.5 million acres of land are
protected in the Mojave National Preserve. Some parks in
the desert include Death Valley, Joshua Tree, and Red Rock
Canyon Parks.

4. Red Rock Canyon State Park
Location: The canyon is located just east of
the southern Sierra Nevada in the Basin and
Range geomorphic province.
Formation: The area subsided over two
periods (65-55 and 20-5 million years ago)
and more than 5,000ft of sediments
accumulated. The El Paso Fault moved and
uplifted the sediments, exposing them to
erosion (Harris).

5. Continued
Features: The strata is divided into two main
groups including the Goler and Ricardo
formations. In the older Goler formation, there
is a great amount of vertebrae fossils present and the formation holds the best vertebrae fossils on
the west side of the Rockies. The newer formation, the Ricardo group, is the reason the area is
famous. Slot canyons, alluvial fans, dry waterfalls, and other desert landforms are
all on display here. The formations of the Ricardo group consist of sandstones, lava flows, sandy
gravels, and lake-deposited silts and clays.

6. Joshua Trees
-Joshua trees are actually not a tree, but a plant belonging
to the Yucca genus (It’s a succulent).
-The average lifespan of these plants is about 500 years.
-These “trees” grow about 2-3 inches per year and get up to
about 40 feet tall.

7. Evolutionary history
The Joshua Tree is thought to have evolved some 5 million
years ago as a distinct variety of the yucca genus, and more
recently, split into two types: bushy short-leaved and arboreal
long-leafed. These two different types match with two types
of the same moth, but it is still up in the air if coevolution (both
species changing reciprocally in response to each other) is
taking place (Smithsonian). For example, instead the trees
could be evolving with the environment and the moth is
evolving with them.

8. Beavertail/Prickly Pear cactus
Perhaps the most common cactus found in California, this
plant creates bright flowers that make it stand out. The
example I found however, is dried up and brown instead of
the usual green color. Its spines are small hair-esque bristles
called glocids that are so fine that each cluster may contain
hundreds of them.

9. Evolutionary history
-This cactus genus originated in South America and the seeds reached North America carried in the
guts of animals who crossed over on a landbridge between the two continents that formed around 3
million years ago.
-During the Pleistocene time period, several Opuntia species evolved to be resilient to the frost. These
cacti thrive in dry sand and conserve water well making them well suited for arid environments.
-As of today there are 61 species of this cactus today in the North America region.

10. Horned lizard
-Also known as the horny toad, horned lizards are flat,
rounded animals part of the Phrynosomatidae family.
-These lizards can live up to 5 years and have many
adaptations. Some of these include: coloration for
camouflage, horns for defence, inflation to look bigger, and
they can even shoot blood from their eye sockets.

11. Evolutionary history
-The Horned lizard is thought to have split off from a shared ancestor with sand lizards around 24
million years ago. Most horned lizard species are well represented in fossils by the early Pleistocene
(Hodges).
-Horned lizards’ ancestors evolved their unique, flat body form and have diversified into few closely
related species. This process is called adaptive radiation.
-The Horned lizards evolved because in the desert, they need lots of camouflage and many defence
mechanisms to protect themselves. Small adaptations such as the way they eat ants as to not get
Stung show on a small scale why these lizards evolved.

12. Red Sandstone
Sedimentary

13. Identification and Characteristics
Location: Bottom of eroding sedimentary cliffs
Identification: Red color, rounded grains of equal size, no foliation or gas bubbles
Minerals present: Mainly quartz, occasionally feldspars and/or mica
Formation: Quartz sand is eroded off of source rocks by weathering and carried by forces such as
wind and rivers. The sediment is compacted with other material and cemented by dissolved material
in water that seeps through it. The red color is caused by iron oxide (Peck).

14. Gneiss
Metamorphic

15. Identification and Characteristics
Location: Desert flatlands just outside park boundaries to the southwest
Identification: Stripes/layers/waves going through entire rock, layered crystals
Minerals present: Mostly feldspars, mica, and quartz, occasionally kyanite, hornblende, and many more
Formation: Gneiss is formed from schist which is created from fine-grained sedimentary source material
such as shale. Another source rock for gneiss could be an igneous rock such as granite. Whatever the
source material is, gneiss is formed from extreme pressure under the earth’s crust (Peck).

16. Vesicular Basalt
Igneous

17. Identification and Characteristics
Location: the eroding badland hills in the northern section of Red Rock Canyon State Park
Identification: dark grey, fine grained, few gas bubbles, lightweight
Minerals present: plagioclase feldspars, olivine, augite, and hypersthene
Formation: Basalt forms from magma/lava rich in iron and magnesium but poor in silica. The magma
erupts from the earth in a volcano or fissure as lava which then cools quickly. Due to the quick
cooling, the grains do not become larger and it remains fine grained (Peck).

18. Disconformity
Formation: This disconformity is
formed when sedimentary layers
are eroded and new layers form
on top.
Example: In the white layers there
are missing sections where
erosion occurred and the red layers
filled in the empty space.

19. Law of superposition
The Law of superposition states that
within a sequence of layers of
sedimentary rock, the oldest layers are
on the bottom and the layers above
are progressively younger in ascending
order.
In the picture there are many layers of
sandstone with the oldest being on the
bottom.

20. References
10 facts about the Incredible Joshua Tree. THE ENVIRONMENTOR. (2021, February 2).
https://blog.tentree.com/10-facts-about-the-incredible-joshua-tree/.
The biogeographical history of the prickly pear Cactus (opuntia sp.). GeorgiaBeforePeople. (2016, July 8).
https://markgelbart.wordpress.com/2013/03/18/the-biogeographical-history-of-the-prickly-pear-cactus-
opuntia-sp/.
Harris, W. (2010). Red Rock Canyon State Park. parks.ca.gov.
https://www.parks.ca.gov/pages/734/files/GeoGem%20Note%2038%20Red%20Rock%20Canyon%20Stat
e%20Park.pdf.
Hodges, W. (n.d.). About Horned Lizards. Digimorph, horned lizards.
http://digimorph.org/resources/horned.phtml.

21. References 2
Jaeger, E. C. (n.d.). Mojave desert. Infoplease. https://www.infoplease.com/encyclopedia/places/north-
america/us-geography/mojave-desert.
Peck, D. (n.d.). The Rock Identification Key. Rock key.
http://www.minsocam.org/msa/collectors_corner/id/rock_key.htm#basalt.
Smithsonian Institution. (2017, August 10). How a tree and Its Moth shaped the Mojave Desert.
Smithsonian.com. https://www.smithsonianmag.com/science-nature/how-tree-and-its-moth-shaped-
mojave-desert-180964452/.
All photos were taken by Bodie Whalen.