When was yosemite valley formed

The entire range is 80 kilometers 50 miles wide and kilometers miles long. Yosemite's highest peak, Mount Lyell, reaches 3, meters 13, ft. The highest peak in Sequoia National Park is Mount Whitney, with an elevation of 4, meters 14, ft. In the Sierra Nevada, granitic rock dominates the landscape. The dramatic granite formations of Yosemite played a significant role in securing National Park status for the area, and they continue to inspire millions of visitors to come and experience Yosemite's breathtaking beauty.

In the Sierra Nevada, visitors encounter a prodigious exhibition of granitic rock, a type of intrusive igneous rock that forms as molten rock slowly cools deep underground. Insulated from the relatively cold air at the surface, the minerals cool and solidify slowly.

This slow solidification allows the minerals to develop crystals that are easily seen. Generally, the slower the magma cools, the larger the crystals will be. The lighter minerals are quartz, orthoclase feldspar, and plagioclase feldspar. The darker specks are mainly biotite and hornblende. Small amounts of the minerals titanite and zircon can also be present. The variable proportions of light to dark minerals found in these rocks result in a fantastic mosaic in an endless sea of granite that helps to distinguish different masses emplaced at different times.

Geologists now believe that the outer shell of the earth is made up of rigid plates that very slowly move around over time. The plates consist of oceanic crust which is relatively thin and dense and continental crust which is thicker and lighter than oceanic crust. When 2 plates collide together, one plate often goes down beneath the other plate in a process known as subduction. This subducted plate carries seawater down with it.

This water gets superheated deep in the earth, and as it rises upwards, it lowers the melting point of the surrounding continental rocks, causing them to melt. The developmental history of the Sierra Nevada has been written and re-written multiple times as new evidence is unearthed and brought into the light. Some of the oldest rocks in the Sierra Nevada are over million years old and are made up of ancient ocean bottom sediments and sub-marine volcanic rocks.

The origins of the amazing granitic rocks of the Sierra Nevada can be traced back to about million years ago. At the time, the land of modern-day California lay at the western edge of the ancestral North American continent, which was in the slow process of moving northwest from its previous location in the tropical latitudes towards its current position. At about Ma, eastward dipping subduction see box to left took over as the eastward-moving Farallon plate began to descend below the North American plate, right in the region where the present day Sierra Nevada is located.

During subduction, as the Farallon plate descended into the mantle, chemical and physical changes resulted in the overriding ancestral North American plate melting. This molten rock rose through the crust in multiple pulses over a period of million years. Some stayed in place, forming large bodies of cooling granite plutons two to 10 miles below the Earth's surface.

Some reached the surface, creating a north-south chain of volcanoes standing as tall as 7, meters 20, ft high. These volcanic mountains were then extensively intruded with more rising magma. Yet, in that ancient time, the area we know as Yosemite today was lying relatively dormant, consisting of gently rolling hills and a few minor streams. One body of water, however, was beginning to assert itself more than the rest. The Merced River wound its way through a shallow indentation in the valley, the genesis of what would eventually shape the valley path.

About 10 million years ago, a full forty million years after we last checked in on the Merced River and the calm, forested landscape, things began to become a lot more geologically volatile. The entire area experienced upheaval, and what once were gentle hills began to thrust upward into more defined peaks.

As well, the Merced River found itself sloping downward, creating an even more defined path through the valley and pushing the valley floor lower as the peaks around it grew taller. About 3 million years ago, the area we know as Yosemite was beginning to change more drastically than ever before. The forested hills that once dominated the landscape were beginning to more closely resemble dry canyons, the burgeoning peaks taking on a more jagged look as the Merced River continued its unrelenting advance.

The geological uplift continued during this time with no signs of stopping, while the climate began to change as well. Temperatures grew colder in the valley, and the once lush landscape began to thin out. Welcome to the Ice Age, where glaciers descended upon the Yosemite Valley, filling the massive valley groove with solid ice.

Parts of the Valley and the surrounding rock were totally encased in ice, with only the tallest peaks jutting above the frost. As the glaciers advanced through the Valley, they took no prisoners, so to speak. Part of the answer lies with ancient glaciers. That still leaves the other half of the story. Once the last glaciers retreated, granite domes became exposed to the elements.