Editing Yosemite Valley (section)

== Natural Yosemite Valley ==
[[File:Three Brothers Yosemite.jpg|thumb|left|The Three Brothers formed from the El Capitan pluton]]

=== Geology ===
{{Unreferenced section|date=July 2022}}{{For|regional information|Geology of the Yosemite area}}

The features in Yosemite Valley are made of [[granite|granitic]] rock emplaced as [[Intrusion|pluton]]s miles deep during the late [[Cretaceous]]. Over time the [[Sierra Nevada (U.S.)|Sierra Nevada]] was uplifted, exposing this rock to [[erosion]] at the surface.

The oldest of these granitic rocks, at 114&nbsp;million years, occur along the [[Merced River Gorge]] west of the valley. The [[El Capitan]] pluton intruded the valley, forming most of the granitic rock that makes up much of the central part of the valley, including [[Middle Cathedral Rock|Cathedral Rocks]], [[Three Brothers (Yosemite)|Three Brothers]], and El Capitan. The youngest Yosemite Valley pluton is the 87-million-year-old [[Half Dome]] granodiorite, which makes up most of the rock at [[Glacier Point]], the [[Royal Arches (Yosemite)|Royal Arches]], and its namesake, Half Dome.
[[File:Washburn Point Yosemite August 2013 003.jpg|thumb|right|Half Dome from Washburn Point]]
For the last 30&nbsp;million years, [[glacier]]s have periodically filled much of the valley. The most current [[glaciation]], the [[Wisconsinian glaciation|Wisconsinian]] was not, however, the most severe. [[Ice age]]s previous to the Wisconsinian were colder and lasted longer. Their glaciers were huge and covered nearly all the landmarks around Yosemite Valley except Half Dome, [[Eagle Peak (Mariposa County, California)|Eagle Peak]], [[Sentinel Dome]], and the top of El Capitan. Wisconsinian glaciers, however, only reached [[Bridalveil Fall (Yosemite)|Bridalveil Fall]] in the valley. The glaciers widened the valley, but much of its width is in fact due to previous stream [[erosion]] and [[mass wasting]] along vertical [[Joint (geology)|joints]] in the valley's walls.

After the retreat of many of these glaciers, a stand of [[Ancient Lake Yosemite]] developed. The valley floor owes its flatness to sediment deposited by these stands (the last glaciers in the valley were small and did not remove much old lake sediment). The last stand of Lake Yosemite was about {{convert|5.5|mi|km}} long and was impounded by a terminal [[moraine]] near the base of El Capitan. It was later filled by sediment, becoming a [[swamp]]y meadow.

The parallel [[Tenaya Canyon]] and [[Little Yosemite Canyon]] glaciers were, at their largest, {{convert|2,000|ft|m}} deep where they flowed into the Yosemite Valley near the base of Half Dome. They also formed [[Clouds Rest]] behind Half Dome as an [[arête]].

Near [[Glacier Point]] there are {{convert|2,000|ft|m}} of mostly glacial sediment with at least six separate sequences of Lake Yosemite sediments. Here, huge and highly erosive pre-Wisconsinian glaciers excavated the bedrock valley floor, and much smaller Wisconsinian glaciers deposited glacial debris.

=== Ecology ===
[[File:Cyanocitta stelleri 08585.JPG|thumb|right|[[Steller's jay]]]]
{{See also|Ecology of the Sierra Nevada}}
The biological community on the floor of Yosemite Valley is a diverse one, with more than 400 species of grasses and wildflowers and thousands of species of insects having been identified there. At the most general level, the valley can be classified as a dry [[Pinus classification|yellow pine]] forest with a number of large open meadows. Plant and animal species that make up a significant part of this natural community include:
* Trees – [[ponderosa pine]], [[lodgepole pine]], [[sugar pine]], [[white fir]], [[incense-cedar]], [[California black oak]], [[interior live oak]], [[coast Douglas-fir]], [[Umbellularia californica|California laurel]], [[bigleaf maple]], [[Salix scouleriana|Scouler's willow]], [[Pacific dogwood]], [[Alnus rhombifolia|white alder]], [[balsam poplar|western balsam poplar]]{{sfn|Schoenherr|1995|p=134}}
* Shrubs – whiteleaf [[manzanita]], mountain misery, western [[azalea]], American [[dogwood]], [[Ceanothus|buckbrush]], deer brush, sierra [[gooseberry]]{{sfn|Schoenherr|1995|p=134}}
* Wildflowers – [[lobelia|Indian pink]], [[soap plant]], [[California poppy]], [[miner's lettuce]], [[purple Chinese houses]], [[Asclepias cordifolia|purple milkweed]], [[Trientalis latifolia|Pacific starflower]], [[western buttercup]], [[pineapple weed]]{{sfn|Schoenherr|1995|p=134}}
* Mammals – [[California ground squirrel]], [[western gray squirrel]], [[chickaree]], [[mule deer]], [[American black bear]], [[bobcat]], [[coyote]]{{sfn|Schoenherr|1995|p=134}}
* Birds – [[dark-eyed junco]], [[mountain chickadee]], [[black-headed grosbeak]], [[white-headed woodpecker]], [[Steller's jay]], [[American dipper]], [[common raven]]{{sfn|Schoenherr|1995|p=134}}
* Reptiles – [[Gilbert's skink]], [[northern alligator lizard]], [[rattlesnake]]{{sfn|Schoenherr|1995|p=134}}
* Amphibians – [[lungless salamander|Sierra Nevada salamander]]{{sfn|Schoenherr|1995|p=134}}