The document summarizes the geological evolution of Yosemite Valley over millions of years. It describes how the valley was formed from seabed rock that was uplifted to form mountains. Glacial activity sculpted the landscape, carving out a U-shaped valley and leaving polished granite. Today, Yosemite Valley is renowned for its towering waterfalls and glacially-carved rock formations like El Capitan.

1. YOSEMITE
The Evolution of
the Valley
Heather McNenny
Geology 103, LTCC
Mark Lawlor
June 20, 2013
“It is by far the
grandest of all the
special temples of
Nature I was ever
permitted to enter.” —
John Muir

2. OVERVIEW
Yosemite has captured the
eyes of photographers and
travelers since it's
increased accessibility by
the Yosemite Valley
Railroad in 1907.
The scenery of the
glaciated landscape
marked the necessity of
preservation as a national
park.
Through this presentation,
the evolution of such
dramatic polished granite
landscape will be
discussed.

3. THE BEGINNING
The origins of the Sierra
Nevada began with rock
forming on the sea floor of
the western part of North
America. This rock was
lifted above sea level and
formed into a mountain
range, surrounded by
volcanoes. The core of the
Sierra Nevada was formed
by the granite caused by
molten rock from the
volcanoes.
After erosion of
sedimentary and volcanic
rock over the granite took
place , green scenery
covered the land. Streams,
valleys, and hills were
prevalent .
The Merced River flowed
through the forests and
hills.
50 Million Years Ago
OhRanger.com

4. 10 Million Years Ago
Uplifting and westward
tilting causing the Merced
River to flow faster and
stronger, cutting into the
valley.
During this time, there was
an abundance of conifers,
beginning the dominance
of the Sequoia tree. The
climate was drier, and cool.
3 Million Years Ago
The climate was getting
cooler due to the
approaching Ice Age. This
affected the forests,
causing them to die off.
There was continual uplift
in the land, causing the
Merced to cut into it's
valley by 3,000 feet.
OhRanger.com

5. Glacier Activity
Glacial events occurred,
filling the valley with ice
and snow completely.
Most of the peaks seen
today were completely
engulfed, though Half
Dome still towered at 900
feet.
The valley was shaped into
a "U" form by the
glaciation.
Cascades were formed
above the valley caused by
the tributaries formed by
the run off of the Merced
River.1 Million to 250,000 years
ago
OhRanger.com

6. The Yosemite Glacier an
event that occurred during
the Tioga Glaciation. This
ice sheet had little impact
to erosion on the valley
because it was very small,
and lacked the powerful
erosion it needed to cut
into the valley.
30,000 Years Ago
10,000 Years Ago
The last glacier melted,
creating Lake Yosemite.
This was something that
occurred after each
freeze/thaw episode.
Eventually the lake filled
with silt, creating the valley
floor. What is left behind is
now called "Mirror Lake." It
is filled by snowmelt in a
similar process.
Mirror Lake
OhRanger.com

7. Yosemite's
Waterfalls
Though glaciers are not
responsible for the
creation of the waterfalls,
they carved the land that
they fall over. Snowmelt
determines the force and
longevity of the falls each
year.
Yosemite Falls is 2425
feet high, making it the
tallest waterfall in North
America. It dries up by the
end of summer.
Ribbon Falls- Typically the
first fall to dry up towards
summer
All of Yosemite's streams
and waterways end up in
the Tuolumne and Merced
Rivers. The Tuolumne feeds
Lake Eleanor and the Hetch
Hetchy Resevoir, which are
water sources for
California. All of the famed
waterfalls of Yosemite end
up in the Merced at the
valley floor.
National Park Service

8. TYPES OF ROCK IN
YOSEMITE
Plutonic Igneous
Rock-
Granite
Granodiorite
Tonalite
Quartz monzonite
Quartz monzodiorite
Quartz diorite
Diorite
Gabbro
Plutonic rocks formed
during Cretaceous Period
Formed by continual
intrusions of magma
beneath the Earths surface
into older rocks.
El Capitan-Consists of El
Cap Granite
National Park Service

9. Volcanic Igneous
Rock
-Basalt Flows
-Latite Tuff
-Latite Lava Flows
Though unable to locate
any for photos, there are
some small amounts of
volcanic igneous rock in
Yosemite Valley. The photo
to the right is an example
of volcanic igneous rock.
Metamorphic Rock can also
be found around Yosemite.
Caused by two northwest
treding belts of
metamorphic rock, on each
side of the batholith before
it's exposure, and creation.
Cathedral Peak
Granodiorite-Photo Credit:
National Park Service
Photo Credit: Mike Dunn
Dunn, Mike. 2006
Yellowstone Ecology
Institute Highlights. National Park Service

10. References
Yosemite National Park CA. National Park Service. Web. June 15,2013.
Yosemite. Yosemite Online.<yosemtie.ca.us> Web. June 15, 2013.
Yosemite National Park. National Geographic. Seventh Edition, 2012.
Web. June15, 2013.
Evolution of Yosemite Valley. OhRanger.Com. Web. June15,2013.
*Visited Yosemite for 3 days and took most information from Rangers, as
well as information boards on hikes and points of interests.
All photos taken by myself unless otherwise credited appropriately
"North America Wall"- El
Capitan