For those of us that find scientific explanations overwhelming - here is our simplified explanation of the amazing phenomenon that formed California's magnificent Yosemite Valley and Waterfalls.
500 Million years ago - For approximately 300 million years layer upon layer of sediment (dirt and organic matter) covered the seafloor to the West of what was to eventually become the North American Continent. During this 300 million years this sediment condensed into rock such as sandstone and limestone.
220 Million years ago - The now condensed landmass on the seafloor moved towards the landmass of the developing continent - pushing under it. This caused the lower layer (the seafloor plate) to become very hot molten rock - which erupted from below to form volcanoes breaking thru the top surface. The molten rock that didn't make it to the surface cooled off below and became Granite - an even more dense form of rock. This happened in a series of pulses over about 140 million years. When the pushes and pulses were over, they had formed the Sierra Nevada Mountain range that ran parallel to the west coast of the continent. Some of these mountains, covered with rock and sediment, may have been up to 13,000 feet.
2 Million years ago - The earth's surface began to cool and the Ice Age began. Glaciers moved from the highest part of the Sierra Nevada down into the deeper Yosemite Valley. The movement of these Glaciers tore away rock and large sections of granite where there were fissures or cracks - leaving dramatic spires and formations. These moving Glaciers widened the valley and made the walls steeper - from which the waterfalls would eventually leap.
20,000 years ago - The last Glacier retreated out of Yosemite Valley passing out beyond El Capitan and Bridal Veil Falls and left a moraine ridge (what is left after the glacier recedes).
10,000 years ago - The basin left by the Glaciers filled with melted Glacier water. Sediment from these glacier lakes settled into the bottom.
80 Million years ago - For a period of approximately 55 million years the top layers of volcanic rock and sediment were eroded away by wind and water. The top layer was carried to the Central Valley - which might explain why it is such a nutrient rich agricultural area. This left the remaining harder granite exposed and mountains of only several thousand feet in height.
25 Million years ago - The valley looked like a typical valley of rolling hills and broad valleys. For the next 15 million years or so land masses meeting under the present San Andreas fault pushed against each other causing more uplift of the Sierra Nevada especially on the eastern side. It is estimated it lifted the mountain peaks on that side 11,000 feet.
10 Million years ago - The increased uplift on the eastern side of the Sierra caused the Merced River to flow down a steeper incline. This increased force of the water caused more erosion and cut deeper into the granite forming a deepened canyon.
Half Dome - is one of a kind formation with no counterpart.
When the Glaciers were at their deepest - all but
the top 700 feet of the dome was covered. The large
dome had a vertical crack. As the glaciers moved slowly
along - they carried away the front 20% of it (it would
sound silly to call it 4/5 Dome). The rounded top was not
formed by glaciers but by exfoliation (gradual peeling
and scaling). The granite of Half Dome is called Half
Dome Granite. The granite type of El Capitan is named
El Capitan Granite.
El Capitan - at 3,000 feet -is the tallest unbroken cliff in the world. The name means "The Chief" and it is formed of the toughest granite of all and therefore resisted the most wear. This formation is a beacon to rock climbers from all over the world who can often be seen climbing its face.