The Evidences of The Theory of Plate Tectonics

The theory of plate tectonics was not always accepted in the scientific community. The theory would originate from Alfred Wegener and his theory would initially be known as continental drift. It would serve as the basis for the theory of plate tectonics. The evidence that the continental plates moved and were not static began to pile on in the early 20th century. Geologists from across the world presented circumstantial evidence that the continents were once joined. Some of that evidence included the very shape of the America’s and Europe and Africa. In particular how it almost appeared as if the continents fit together like a jigsaw puzzle. On top of this, there was proof that fossils and rock strata on both sides of the Atlantic Ocean were similar. However these pieces of evidence alone were not enough to solidify an explanation for such a grand claim.

One of the best pieces of evidence that would come to light that supported this theory was Sea Floor Spreading. Sea Floor Spreading is when magma is forced up from inside the earth, underwater, at a particular ridge, a common example being the Mid-Atlantic Ridge. This molten rock forming new underwater formations would be forced to either side as yet even more molten rock continued to flow out. In order to explain where this new material was if Earth had been continually growing, there must be something consuming the older land. This was explained by seduction, wherein a plate moves underneath another due to forces like gravity and magnetism. This occurs in areas known as Zones of Subduction, and the particular geologic feature where actual subduction occurs between plates.

Evidence that has been used to support this theory includes the dating of multiple protruding ridges out of ridges like the Mid-Atlantic. It was found that the further away from the center of the Atlantic, horizontally, the older the undersea formations were. This helped reinforce the idea that new material came up and out from the middle ridge and pushed older material outwards, which would later be subducted and recycled. The forces of plate tectonics have shaped California’s landforms in many ways. The main tectonic plates that influence California the most are the North American and Pacific plates. One plate that was subducted millions of years ago was the Farallon plate. When it was subducted under the North American plate, it created a volcanic chain on the eastern edge of California. This would eventually form the Sierra Nevada. The San Andreas Fault system also played a large part in California’s landform development. This is where the Pacific and North American plates slide along each other as a strike-slip fault. Regions like the Basin & Range, contain remnants of volcanic activity as sediment deposited in the Central Valley and more southern regions millions of years ago. This has aided in the fertility of California.

The main factors that determine an earthquakes extent of damage are: The Magnitude of the Earthquake. It’s reading on the Richter scale to determine how strong the earthquake is. Then how far a given area is away from the epicenter; or area directly above the exact point where an earthquake originates underground (the hypocenter), the density of the population of an affected area. Logically it follows that higher density areas have more casualties and are likely to have more structures overall that could be affected by the earthquake. More human and material damage overall. Then comes the preparedness level of the city, county, state and country where it occurs or is affected. More developed regions of the planet are able to maintain buildings that are somewhat earthquake proof and also maintain emergency services and experts able to react to an earthquake in a timely fashion, therefore limiting the human toll as much as possible.

Material damage like buildings can be prevented up to a reasonable level where truly massive earthquakes cannot be engineered against, however most small earthquakes do not cause severe structural harm to buildings. After this is when the earthquake occurs over the course of a day. For example, during the day people are more likely to be out and about and better able to react to an earthquake. Also, emergency services, although technically always on standby would have a much easier time operating with daylight in any kind of rescue or salvage operation. If the earthquake occurs at night, it is entirely possible and even probable that people could be trapped in the own homes, if the earthquake is severe enough.

Finally the type of soil plays a role as well. Soft soil is susceptible to liquefaction. This is when the sediment, on which buildings are built and people live, loses its strength and acts more as a liquid. Of course buildings cannot be supported by this liquid-like soil and can collapse, killing many inside. Coast Ranges Central Valley Sierra Nevada Great Basin Geologic Formation Pacific plate sliding against N. American Plate Formed as inland sea initially, sediment dumped into creating rich land. Subduction of Farallon Plate, Magma formed from subduction. Uplifting and extension of surrounding landmasses Weather Mild, Mediterranean Climate Warm Mediterranean. Cold, Highland Climate Hot, Arid/wet depending on elevation. Some parts affected by rain-shadow Economic Activities Tourism, Sea Trade, Agriculture, Education Agriculture, manufacturing Tourism, Recreation, Farming, Mining, Manufacturing.