Plate tectonics was first suggested as a theory by the geologist Alfred Wegener in 1915 when he proposed the concept of continental drift. Back in the geological past, what is now South America, Africa, Australasia and Antarctica fitted together into a supercontinent known as Gondwanaland; with North America, Europe and Asia fitting into another supercontinent known as Laurasia. (OCR AS/A2 Geology, Mugglestone et al, 2008). These were once believed to be joined to form one major central global landmass known as Pangaea (Introducing Geology, Graham Park). But now due to the global distribution of these major plates it has been proposed by Wegener and his successors that convection currents in the mantle are the cause of the movement of plates.
The underlying ideas that Wilson built his theory on were proposed by Alfred Wegener in 1912 with his Theory of Continental Drift. Tuzo Wilson was able to provide a way to explain how the continents were able to move apart that Wegener could not explain when he had proposed his idea. Scientists had believed that based on the evidence Wegener had provided it did appear that all of the present day continents had somehow been connected together. The way that the coasts of Africa and South America appear to fit together nicely in addition to fossil evidence of large tortoises and other animals being found near the edges of the continents. Alfred could not explain how the huge masses of land could have moved so far.
The Sierra Nevada Mountains on the Pacific coast of North America and the Andes on the coast of South America were cited. Wegener also suggested that India drifted northward into the Asian continent thus forming the Himalayas. Many other scientist provided evidence toward this theory of a “continental jigsaw”, this evidence included geological matches in the rock type on two different continents coastlines found thousands of miles away e.g. Scotland and Canada and South America and Africa. Fossil evidence was also provided; trilobites of the same species found in Canada and Scotland and also, coal deposits were located in Antarctica.
Plate tectonics (also known as the conveyor belt principle) is a scientific theory that describes the large-scale motions of the Earth’s lithosphere, building on concepts from the theory of continental drift (movement of the Earth’s continents relative to each other). The lithosphere is broken up into 7 main tectonic plates which move from 0-100mm annually. It is thought that the continents once formed a single land mass called Pangea that drifted apart, this is the start of the main idea of plate tectonics. In 1596, Abraham Ortelius first made the speculation that continents might have ‘drifted’ but the concept was developed further by Alfred Wegener in 1912. Presently, Earth Scientists agree on the observation and assumption that the plates have moved with respect to one another, but they still debate as to how and when.
How to predict an volcanic eruption Ground Deformation Ground deformation is the change in shape that happens before during or after a volcanic eruption. This happens because the sides of the volcano change shape because the magma in many ways to measure the change of shape of the volcano, like leveling, triangulation and more recently using continuous Global Positioning System (CGPS). It is also possible to use lakes as large tilt meters. Tilt meters measure the tiny degrees of tilt or slope on land. This is one of the oldest methods of knowing when ground deformation was caused because of rising lava.
Plate Tectonic Theory What is Plate Tectonics? Plate tectonics is the main force that shapes our planet’s surface over a long period of time the study of how the Earth's crust is shaped by geological forces. It relies on the understanding that the crust is divided into large pieces, or plates, that sit on the molten interior of the planet. Currents within the interior cause the plates to move, which causes many different geological events, including earthquakes and the forming of mountains and volcanoes. Understanding how plates move and interact is the main purpose of plate tectonics.
It wasn’t until Alfred Wegener (1912) presented his theory of continental drift that a reasonable explanation was available. As this theory gained acceptance, although slowly at first, through the 20th century geologists were able to gather evidence to produce maps showing the arrangement of the Earth’s major continents at different periods of its history. These paleo-maps are of great importance for those who study evolution, as the presence and break-up of so called ‘super-continents’ in the past offered an explanation to the disjointed distributions of many terrestrial animals, both extant and fossils. Scientists pre-Wegener postulated that sister clades somehow travelled across large oceans, via land-bridges that are geologically improbable, to explain their presence in both Africa and S. America. What was now a possibility is that these animals were simply on the opposite sides of one continent as it split down the middle to form the Atlantic Ocean.
J. Subbiondo © 2004The CrustThe outer layer of the Earth is called the crust. It is made up of rock that floated to the surface when the Earth was formed. It is not a continuous layer, but is made up of large masses called tectonic plates.These plates drift slowly across the Earth's surface (tectonic means moving).The movement of these plates creates mountains and valleys.At weak points in the crust, it causes volcanic eruptions. And when plates bump into each other, earthquakes occur -- emitting shock waves or vibrations called seismic waves. The crust is the Earth's coldest layer.
The reason for the movement is convection currents originating in the core caused by radioactive decay. Knowing the theory of plate tectonics is a useful tool in understanding the distribution of earthquakes and volcanoes as they correlate very closely. If we map out the location of major earth quakes, location of active volcanoes and a map of general plat tectonic, the 3 would overlap. This gives us a general idea of locations and correlations. Each boundary between 2 plates have the capability of being a different type of boundary.
The strength, distance, and length of the wind gusts determine how big the ripples become. The crest of a wave is its highest point. Wavelength is the horizontal distance, and wave height is the wave’s vertical distance. The last type of motion is currents. Currents are the ocean’s constant flow of water that is pushed on by either the wind or from tides that are caused by the moon’s gravitational field.