Evaluate How Plate Tectonic Theory Helps Our Understanding of the Distribution of Seismic and Volcanic Events (40 Marks)

In 1596- Abraham Ortelius took note that the coastlines of the continents seemed to be too fitting together. He initiated a theory that stated that the continents were probably joined at one point in time and were torn apart between Europe and Africa. In the year of 1912, Alfred Wegener stated that the continents were once joined in a supercontinent called Pangea.

This lab uses earthquake data to construct profiles of two convergent boundaries: the Tonga Trench and the Peru-Chile Trench. Where two tectonic plates converge, if one or both of the plates is an oceanic lithosphere, a subduction zone will form. When crust is formed at a mid-ocean ridge, it is hot and buoyant meaning it has a low density. As it spreads away from the ridge and cools and contracts, or becomes denser, it is able to sink into the hotter underlying mantle. When two oceanic plates collide, the younger of the two plates, because it is less dense will ride over the edge of the older plate. The density of the

One evidence of this theory is molten material. Molten Material is magma erupting from mid-ocean ridges. Alvin the submarine found weird rocks shaped like pillows or toothpaste. This tells us this magma cools quickly underwater. Another type of evidence are magnetic stripes. Magnetic stripes are patterns in the ocean floor to prove Earth’s magnetic field has reversed itself in history. Scientist also looked at the “magnetic memory” of the rocks. Scientist drilled pipes through water to drill holes into the ocean floor. Scientists discovered that the older rocks were further away and younger rocks were closer. Those were the three types of evidence that scientist used to support the theory of Sea Floor Spreading.

The plate tectonics theory was made by a German named Alfred Wegener. He stated that a single continent existed about 300 million years ago named Pangaea and that it split into two continents of Laurasia in the north and Gondwanaland in the south. Today’s continents were formed by further splitting of the two masses.

The theory of plate tectonics was first developed by Alfred Wegener. He concluded that the continents seem to have a similar shape and could potentially fit together. This suggested that they were at one time joined together as part of 2 super continents called Gondwanaland and Laurasia was in the north. This theory was said to be proven by the discovery of fossilised remains of a mesosaurus that were found on the coasts of Brazil and Gabon. Sea floor spreading is another theory that supports the idea of plate tectonics; this theory discovered that rock is being formed under the ocean as a new sea floor. Sea floor spreading was shown in the Atlantic, where it is believed the Eurasian and North American plates are moving apart on a

Volcanoes can be found throughout the entire world and are formed when there is a rupture in the mantle of the Earth's crust. This effect allows the output of volcanic lava, ash, and various types of gases. These tectonic plate breaks are normal, the planet Earth is divided into 17 tectonic plates and consistently move against each other forming shifts from low to high intensity. It can cause displacement of earth or water.

In junior high school, I have learned the Continental Drift Theory, and my geography teacher told me there was a new theory based on the Continental Theory, i.e. Plate Tectonics. I accessed to the Internet to find the information about Plate Tectonics.

To support the theory of continental drift is through topography, surveying the floors of oceans, charts of rock magnetism, and statistics on rock ages (Trefil & Hazen, 2010). At one time scientist believed that the deep ocean floors were flat; accumulating the sediment that progressively wore away from the prehistoric landmasses (Trefil & Hazen, 2010). However, they discovered steep-walled valleys and elevated highlands. This was evidences that just as the continents are transformed and are active, so to is the seafloor (Trefil & Hazen, 2010). The Mid- Atlantic Ridge, positioned in the central part of the Atlantic Ocean, is recorded to be the longest mountain range on this planet. Volcanoes, lava flow, and earthquakes are a source of

James Hutton was the first scientist to address the Earth was millions of years old, as well as alive and is continuously being formed. Charles Lyell popularized uniformitarianism, and believed the Earth was being shaped by slow moving forces. Alfred Wegener introduced the foundation for the theory of continental drift. Wegener was one of the first to recognize and have an understanding of how the Earth works which required data and information from earth sciences. In the 1960s, the theory for the continental drift became known as the theory of plate tectonics or plate building.

If new crust is indeed being produced at the rifts, where does the additional older crust go?

The extent to which tectonic processes represent a hazard depends upon when and where they are experienced (40)

7. What is the relationship between plate tectonics and the ocean floor—seafloor spreading, for example?

Scientist are struggling to come up with a widely accepted model that will explain the role of non-vertical strike-slip fault segments, crustal movement and deformation within Pacific –North American plate boundary. Multiple methods of analysis are being used; some of which are described below.

The beginning of the start of sea floor spreading in Iceland occurred about sixty million years ago when the North-Atlantic Ocean began to open. At this time, the North American plate along with the Eurasian plate moved east and westward at approximately one centimeter per year in each direction. This has created new basalt, and ninety-two percent of Iceland’s surface area is made up of basalt. The Mid-Atlantic Ridge contains a series of spreading centers showing the ridge crest, offset in numerous areas located near transform faults that illustrate the seismically active parts of fracture zones. The dating of spreading has been recorded by magnetic lineaments, with magnetic observations from the ocean floor south of Iceland being taken advantage of in the early understanding of the ideas of plate tectonics. The largest offset is the Charlie-Gibbs Fracture Zone in the south of Iceland, where it is offset at three-hundred and fifty kilometers. To the north of this area is where the ridge is relatively straight and the depth of the water decreases at a constant rate towards Iceland. At

After World War 2, the U.S. Office of Naval Research intensified efforts in ocean-floor mapping, leading to the discovery of the Mid-Atlantic Ridge to be part of a continous system of mid-oceanic ridges on all ocean floors, prompting Harry H. Hess to suggest the theory of sea-floor spreading. The oldest fossils found in ocean sediments were only 180 million years old and little sediment were accumulated on the ocean floor. Thus, he suggested that seafloors were no more than a few hundred million years old, significantly younger than continental land due to