The geologi sejarah Point Lobos , mengenai header Point Lobos di Central Coast di Monterey County, California | Monterey County]], California.
The geology of the area covers the last 80 million years. The oldest rocks exposed here formed during the Cretaceous Age of the Mesozoic Era, when dinosaurs still roamed the earth and pterodactyl dominated the sky. This area forms part of the Salinian Block, a piece of continental crust trapped on the border of a transformation between the Pacific and North America.
Point Lobos is a common name for landform and area, which includes Point Lobos State Reserve on land; and two adjacent marine protected areas: Lobos, State Marine Reserves (SMR) and Lobos State Marine Conservation Area .
Video Geological history of Point Lobos
Santa Lucia Granodiorit
During the Cretaceous period the west coast of North America is the site of an active chain of volcanoes. Active subduction creates magma chambers that feed the volcano. The magma cools slowly at a depth of 10-20 km beneath the surface of the earth to form a granite intrusion known as Granodiorit Santa Lucia. Granodiorite is made of quartz mica, orthoclase, plagioclase, amphibole, and biotite. Radiometric data show and age of 79.5 million years for granodiorite. Over the next 30 million years, the Granodiorite Santa Lucia rose to the surface of the earth and eroded. Granodiorite provides basement rocks for the sedimentary sediments of young Point Lobos.
Maps Geological history of Point Lobos
Carmelo Formation
About 55 million years ago, on the Epoch Paleocene Period of Paleogen (the Kenozoic Era), an undersea crater that penetrates the granodiorite basalt rocks and the sediments comprising the Carmelo Formation are stored. The Carmelo consists of pebbles for rocky conglomerates, rough and medium rough sandstone and mudstone. The gravel that is included mostly comes from the volcano. They are carried by rivers flowing in the volcanic plains. During transportation their coarse shapes become round and polished. Sediments are deposited as submarine landslides and turbidity flows.
Fossils include shells, burrows made by worms, and mysterious seaweed fossil traces. Shells, gravel, and other materials are deposited, along with sand and mud, inside the submarine's canyon walls and become supple. The Carmelo Formation is the second big rock type in Point Lobos. Carmelo is easily recognizable along the southern coast of Point Lobos.
Sea terrace
About 18,000 years ago, during the Pleistocene Period in the Quarter Period (the Kenozoic Era), the Pacific Ocean level was much lower than it is now (as more water is in the poles of ice and continental glaciers). Deep canyon submarines were cut in the Monterey Bay area, as an extension of the Salinas River.
During the Late Kenozoic Era, due to the ongoing transpression of the Pacific Plate to the American Plate along the nearby San Andreas Fault Zone, there was a continued increase of the entire California coastline, so the erosion action of ocean waves cut off this terrace in the Monterey Bay area. Pleistocene sea terraces consist of clay, mud, sand and gravel with basal gravel misalignment on rocks. The creation of rising sea terraces that began to emerge during the Pleistocene Epoch continued throughout (now) Epoch Holocene from the Quaternary Period due to transpression from the Pacific Plate to the American Plate. During the October 1989 Loma Prieta earthquake, Monterey Bay's ocean terrace was increasingly elevated. Both Monterey and Santa Cruz have a classically elevated wave-cutting beach with a few pairs of uplifted and exposed sea terraces.
Sand and gravel
Rocks of the fourth and the youngest types are sand and gravel. These are found along the coast. Once again it has been created by the action of waves and rain that causes erosion of other rock types. Age of this type of stone varies from ten thousand years ago to today.
See also
- Geocities of Monterey County, California
- California geological formation
References
External links
- California State Parks: the official website of Point Lobos State Reserve
- Monterey County Convention and Visitors Bureau: Point Lobos tourism information
- Onscenicroutes.com: Lobos Point and Sea and Land Battle
- Initiative of Marine Life Protection Act
- CalOceans
- Americansouthwest.net: Point Lobos State Reserve - description, maps, photos.
Source of the article : Wikipedia
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