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

Evidence for Plate Tectonics.

Extracts from this document...


Evidence for Plate Tectonics Into the 1900's, many scientists believed that as the earth cooled after the Big Bang, the planet's surface contracted and wrinkled like the skin of a raisin. The 'raisin' theory implied that mountain ranges like the Himalayas were forced up by the wrinkling process. This theory assumed that all of the features on earth had formed during one cooling event and that the planet was relatively static, changing little as the cooling (and wrinkling) slowed to a halt over billions of years. Alfred Wegener, a German geophysicist and meteorologist, was not satisfied by this explanation. His ideas drew on the widely recognized fact that Africa and South America appeared to fit together like jigsaw puzzle pieces. He collected data from the continents on both sides of the Atlantic, finding that fossils and rock types along the eastern coast of South America matched those on the western coast of Africa. ...read more.


The same year that Hess proposed his theory, the U.S. Navy published a report that summarized findings concerning seafloor magnetism. During World War II, ships dragging devices to measure magnetism found bands of alternating strong and weak magnetism in the rocks of the seafloor (originally these magnetometers had been designed to locate submarines). These bands, irregular in width, not only paralleled the mid-ocean ridges, but were patterned symmetrically about the crest of these ridges. The magnetism was caused by the presence of magnetic minerals in the rocks. Scientists were not surprised to learn that seafloor rocks contain the magnetic mineral magnetite. In 1963, Fred Vine and Drummond Matthews, two British geologists, joined the map of the Mid-Atlantic Ridge with the symmetric bands of magnetism on the seafloor. Where the Navy ships mapped strong magnetism, rocks showed normal polarity; where they mapped bands of weak magnetism, the rocks showed reversed polarity. These strongly patterned paleomagnetic reversals recorded on the seafloor provided the necessary proof of Hess's seafloor spreading. ...read more.


3. There is a large amount of seismic, volcanic, and geothermal activity along the conjectured plate boundaries. This is shown clearly below in the figure labelled "Crustal plate boundaries" where the epicentres of earthquakes above Richter magnitude 5.0 are plotted for a 10-year period. The concentration is striking, and indeed this plot serves to define the plate boundaries extremely well. 4. There are ridges, such as the Mid-Atlantic Ridge where plates are separating that are produced by lava welling up from between the plates as they pull apart. Likewise, there are mountain ranges being formed where plates are pushing against each other (e.g., the Himalayas, which are still growing). "Crustal plate boundaries" Today, much of the evidence the plate tectonics is acquired with satellite technology. Through use of the Global Positioning System (GPS) and other satellite-based data collection techniques, scientists can directly measure the movement and speed of plates on the surface of the earth. Speeds range from 10-100 mm per year, confirming the long-held belief that plates move at a slow but constant rate. ...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)

    Tectonic earthquakes occur anywhere in the earth where there is sufficient stored elastic strain energy to force two resisting plates to move against each other, thus releasing the pressure. The sides of a fault only move past each other smoothly and aseismically if there are no irregularities that could cause friction.

  2. Marked by a teacher

    Volcanic & Seismic events are pieces of evidence proving that the plate tectonics theory ...

    4 star(s)

    plates diverge the heat created in the upper mantle escapes through the broken crust forming new land through a fissure eruption. These eruptions thus prove the validity of the plate tectonics theory, the constructive margins especially, not only showing that land is being destroyed, but also created while these plates diverge.


    These plates are categorised into 2 different sorts, continental and oceanic, the oceanic crust is more dense than continental and consists of silica and magnesium and is also made up of younger rock.

  2. Plate tectonics

    Moreover, the neighboring Tibetan Plateau, at an average elevation of about 4,600 m, is higher than all the peaks in the Alps except for Mont Blanc and Monte Rosa, and is well above the summits of most mountains in the United States.

  1. Plate Tectonics.

    This is quite similar to lava lamps. The drawing below shows that the hotter areas in the magma are rising, and then fall as they cool. Wegener was browsing in the university library when he came across a scientific paper that listed fossils of identical plants and animals found on opposite sides of the Atlantic.

  2. Plate Tectonics

    Jai Mehta 11AY Conservative or transform Boundaries are places where plates slide past each other.

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

    Furthermore, a reason behind the theory of plate tectonics is the idea that the temperature increases the closer you are towards the Earth?s core and the heat released within the mantle by radioactive decay of the elements helps to create convection currents.

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

    The trends of several major mountain ranges also support the hypothesis of continental drift. These mountain ranges seemingly end at the coastline of one continent only to apparently continue on another continent across the ocean. The folded Appalachian Mountains of North America, for example, trend northeastward through the eastern United States and Canada and terminate abruptly at the Newfoundland coastline.

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