• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Evaluate the evidence that lead to the formation of the concept of which developed the theory of plate tectonics.

Extracts from this document...

Introduction

Evaluate the evidence that lead to the formation of the concept of which developed the theory of plate tectonics. The earth is made up of 4 parts: Crust, Mantle, Outer core and the Inner core. The crust is compared to the earth a thin 'skin' it floats upon the mantle and is split into 2 different parts. The oceanic crust (sima) is a layer consisting mainly of basalt, averaging 6-10km in thickness, the continental crust (sial) can be 70km thick, and the crust is separated from the mantle by the Moho discontinuity. The crust and the rigid top layer of the mantle are collectively known as the lithosphere. The mantle is mainly composed of silicate rocks, rich in iron and magnesium. Apart from the top layer the rest of the rocks, the aesthenosphere, are kept in a semi-molten state. The mantle extends to a depth of 2900km where temperatures may reach 5000oC. These high temperatures form convection currents. The core consists of iron and nickel. The outer core is semi-molten while the inner core is solid; the temperature of the core, which is 6371km deep, is 5500oC. ...read more.

Middle

All these pieces of evidence have pointed towards the continents once being joined or by having some sort of bridge between them. Wegener's theory of continental drift was dismissed by several scientists as he was not considered a specialist in any of the sciences he had used to develop his theory and he could not explain how solid land masses had managed to change their positions, he was unable to suggest the mechanism for the drift. Wegener's theory of Continental drift. Since Wegener put forward his theory of continental drift there have been several pieces of new evidence that support his unproven theory. The discovery of the Mid-Atlantic ridge, which is a range of mountains that run the length of the Atlantic Ocean, found by Ewing in 1948 during an investigation of islands in the Atlantic has shown that the mountain range consists of fairly new volcanic rock - not ancient rock as previously presumed. This evidence proves that there is still physical activity of the earth's crust still occurring today. Studies of palaeomagnetism in the 1950's showed that the rocks that were either side of the Mid-Atlantic ridge had small deposits of iron that were aligned along the earth's magnetic field. ...read more.

Conclusion

The continental plates are older, less dense and consist of silica and aluminium. As a result of the convection currents these plates are moved about either towards, away or sideways to other plates resulting in Fold Mountains, volcanoes, earthquakes and other major landforms. Due to the lower density of the continental crust when the continental and oceanic crusts collide the oceanic crust is forced downwards into a subduction zone where the rock is heated and turned back into a semi-molten state, which rejoins the mantle or increases the pressure in the mantle and causes eruptions. This has occurred in the Pacific Ocean around Asia. When plates move apart to form constructive plate boundaries magma from the mantle surfaces and cools to form new rock between the plates forming mid-ocean ridges and volcanoes. Plate tectonics Using all the evidence that has been collated over the years has let us contrive a reliable theory which looks at all possible ideas that may have been overlooked it has lead us to complete a detailed model of the earth's surface and the explanations for landforms and major natural hazards i.e. Earthquakes and volcanoes. Gary Woodsford Geography 02/05/2007 1 ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Hazardous Environments section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Hazardous Environments essays

  1. Marked by a teacher

    Discuss the degree to which the theory of plate tectonics is supported by seismic ...

    5 star(s)

    Normal faults occur mainly in areas where the crust is being extended such as a divergent boundary. Earthquakes associated with normal faults are generally less than magnitude 7, are often submarine and present a minor hazard due to their distance from human habitation.

  2. OUTLINE THE EVIDENCE TO SUPPORT THE THEORIES OF PLATE TECTONICS & CONTINENTAL DRIFT

    This shows that there have been new rocks generated along the ridge during the history of the earth leading many scientists to believe that the plates of the earth were increasing in size. In 1962, Hess studied the age of the rocks from the middle of the Atlantic outwards to the shores of North America.

  1. Chromatography Investigation

    These two substances generated identical retention factor values, thus, the yellow-orange extract was probably beta-carotene. Beta-carotene's non-polar nature allowed it to dissolve into the mobile non-polar solvent and caused it to have little affinity to enter the stationary phase. As a result, beta-carotene was able to travel down the column faster than the other components.

  2. Evaluate the evidence for the Earths structure & plate tectonic theory

    There was no evidence that pointed towards the planet growing in size as the ocean floor builds up, therefore, oceanic crust must be consumed elsewhere. This led to new questions, such as how & where is this happening? These questions led to the discovery of huge trenches where large areas

  1. Plate Tectonics.

    About 300 million years ago, claimed Wegener, the continents had formed a single mass, called Pangaea (from the Greek for "all the Earth"). Pangaea had rifted, or split, and its pieces had been moving away from each other ever since.

  2. Continental Drift - the evidence that supports the theory.

    It seems hard to believe that such similar organisms would exist so far away from each other, or that they could have swam from one continent to another. It is more likely that these life forms once lived all together on a single continent, as shown in the following image.

  1. Volcanic and seismic events are major pieces of evidence towards proving that plate-tectonics theory ...

    This suggests that the two continents were joined together for some period of time prior to 550 million years ago. 2. Another thing to look for is continuity of geologic features such as mountain chains. Figure 4.5 shows a reconstruction of the continents at a time when they were joined together in the supercontinent Pangaea.

  2. To what extent can the theory of plate tectonics explain global distribution of ...

    The Earth?s crust is made up of over 50 plates, all of them move at different rates and directions. Most of them are in motion moving on average 5 to 10cm per year but some move faster up to 18cm per year.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work