source1: http://www.
source2: http://www.nps.gov/yose/
Human presence in Yosemite can be traced before the arrival of the Europeans. Way before Yosemite became a public attraction, a Native American group called the Ahwahneechee lived there for generations (National Park Services). Interestingly, the name “Yosemite” is borne out of the Native Americans who lived in and around the area. The name literally means “those who kill” denoting the bravery and aggressivenes of the Native Americans who lived in the area (Yosemite.ca.us). Then in the mid-1800s, Europeans arrived in Yosemite (National Park Services). The subsequent California Gold Rush, as well as the corresponding Indian Wars in California drove away the Ahwahnaeechee and the Yosemite Indians out of their homeland in and around the national park(Yosemite.ca.us). According to the information provided by National Park Services, Yosemite has been a rugged place for a long time, as the rugged terrain proved to be a challenge to many early travelers. Only about 650 travelers in the mid-1850s to mid-1860s made the journey to Yosemite Valley by horseback or stage (National Park Services). Construction of the Yosemite Valley Railroad (from Merced to El Porto) in the year 1907 made traveling to Yosemite easier; the construction of this railroad increased the amount of visitors. President Abraham Lincoln signed an 1864 bill granting Yosemite Valley and the Mariposa Grove to the State of California. John Muir helped spark the creation of Yosemite National Park in 1890 (National Park Services). Throughout history, glaciation was a major geological force that shaped the Yosemite landscape. This information below describes how Yosemite looked like throughout history and how it gradually formed or transformed:
500 to 200 million years ago
The Sierra Nevada region
was once submerged beneath a sea. Sediments slowly accumulated on the ocean
floor, growing thousands of feet thick and compressing the layers into
sedimentary rock (ohRanger).
200 to 80 million years ago
A slab of the Earth's
crust, called a plate, began to slide under the North American continent in a
process called subduction. Deep within the earth, tremendous heat and pressure
caused the downgoing plate to melt into magma. The magma rose toward the
surface, where some of it erupted to form a mountain chain of volcanoes. Much
of the magma cooled underground to become granite (ohRanger).
60 to 10 million years ago
After subduction ceased,
prolonged erosion stripped away the overlying volcanic rocks and exposed the
granite. The land destined to become Yosemite National Park was made up of low
mountains with shallow river-cut canyons. Hardwood forest flourished (ohRanger).
10 million years ago
Over the next 5 million
years, the Sierra Nevada, California's "backbone," rose. The Sierran
block uplifted, tilting westward, increasing the Merced River began to carve a
narrow canyon. Redwood forests flourished (ohRanger).
3 million years ago
The Merced River carved its
canyon deeper, while its tributaries cut the land more slowly. Forests began to
thin as the Ice Age approached (ohRanger).
1 to 2 million years ago
A series of large glaciers
flowed from the crest of the mountain range into the river canyons. Glaciers
repeatedly filled the "V"-shaped Yosemite Valley, widening, deepening
and carving it into a "U" shape, forming hanging valleys from which
waterfalls now cascade (ohRanger).
15,000 years ago
Temperatures warmed and the
last glacier retreated from Yosemite Valley. Its terminal moraine (rock debris)
dammed the Valley 14,000 to 15,000 years ago, creating a shallow lake. Sediment
eventually filled the lake, which became the flat valley floor we see today
(ohRanger).
Today
The same process of
sedimentation continues at Mirror Lake, which is even smaller today than in
this photo. Soon, sediment will completely fill in the lake, creating a meadow.
Water and gravity continue to shape Yosemite's landscape. Events like the Middle
Brother rockfall of 1987 and the flood of January 1997, were the most dramatic
in the recorded history of the park. Be aware that rocks can fall at any time
(ohRanger).
There were many things that
were native to the Yosemite Valley, which included black oak acorns and some
types of fish; they used those native items to trade for obsidian, rabbit skin,
and pine nuts (ohRanger). Due to the discovery of gold in the Sierra Nevada
foothills in 1848, many Native Americans were murdered and subjects of theft. Thousands
of gold seekers were attracted to the Yosemite Valley and eventually it led to
the Mariposa War in 1851. The Mariposa Battalion entered Yosemite and was the
first non-Indians to be recorded as entering the Yosemite Valley (ohRanger).
Historically, Yosemite has always been a beautiful place; word of Yosemite's
beauty gradually spread, and in 1855, the first party of tourists arrived.
Yosemite and the Mariposa Grove became the first public preserve in the United
States due to Californians persuading Congress and President Lincoln in the
1860s (ohRanger).
Today, it is known as one
of the “crown jewels” of the national park system, which arguably have impacted
the way people and the government protect it (by giving more funds and added
security to the areas) while also encouraging a lot of people to visit, thereby
increasing the ecological footprint to the detriment of the living organisms in
Yosemite (yosemitepark.com). At this point in history, the National Park
vividly illustrates the effects of glacial erosion of granitic bedrock,
creating geologic features that are unique in the world. Repeated glaciations
over millions of years have resulted in a concentration of distinctive
landscape features, including soaring cliffs, domes, and free-falling waterfalls.
There is exceptional glaciated topography, including the spectacular Yosemite
Valley, a 914-meter (1/2 mile) deep, glacier-carved cleft with massive sheer
granite walls. These geologic features provide a scenic backdrop for mountain
meadows and giant sequoia groves, resulting in a diverse landscape of
exceptional natural and scenic beauty. From the UNESCO World Heritage site,
Yosemite is known for:
- exceptional natural beauty, including 5 of the world's
highest waterfalls, a combination of granite domes and walls, deeply
incised valleys, three groves of giant sequoia, numerous alpine meadows,
lakes, diversity of life zones and variety of species.
- Glacial action combined with the granitic bedrock has
produced unique and pronounced landform features including distinctive
polished dome structures, as well as hanging valleys, tarns, moraines and
U-shaped valleys. Granitic landforms such as Half Dome and the vertical
walls of El Capitan are classic distinctive reflections of geologic
history. No other area portrays the effects of glaciation on underlying
granitic domes as well as Yosemite does.
