Science help?

Question

Plate Tectonics
Sea Floor Spread
Continental Drift

I want to know more about the things I listed. Is it that hard to figure out?

Answer 1

Plate tectonics is a theory of geology that has been developed to explain the observed evidence for large scale motions of the Earth's lithosphere. The theory encompassed and superseded the older theory of continental drift from the first half of the 20th century and the concept of seafloor spreading developed during the 1960s.

The outermost part of the Earth's interior is made up of two layers: above is the lithosphere, comprising the crust and the rigid uppermost part of the mantle. Below the lithosphere lies the asthenosphere. Although solid, the asthenosphere has relatively low viscosity and shear strength and can flow like a liquid on geological time scales. The deeper mantle below the asthenosphere is more rigid again. This is, however, due not to cooler temperatures but to high pressure.

The lithosphere is broken up into what are called tectonic plates—in the case of Earth, there are seven major and many minor plates (see list below). The lithospheric plates ride on the asthenosphere. These plates move in relation to one another at one of three types of plate boundaries: convergent or collision boundaries, divergent or spreading boundaries, and transform boundaries. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along plate boundaries. The lateral movement of the plates is typically at speeds of 0.66 to 8.50 centimeters per year.

Seafloor spreading occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Seafloor spreading helps explain continental drift in the theory of plate tectonics.

Eariler theories (e.g., by Alfred Wegener) of continental drift were that continents "plowed" through the sea. The idea that the seafloor itself moves (and carries the continents with it) as it expands from a central axis was proposed by Harry Hess from Princeton University in the 1960s. The theory is well-accepted now, and the phenomenon is known to be caused by convection currents in the plastic, very weak upper mantle, or asthenosphere.

Continental drift refers to the movement of the Earth's continents relative to each other.

Frank Bursley Taylor had proposed the concept in a Geological Society of America meeting in 1908 and published his work in the GSA Bulletin in June 1910.[1] Abraham Ortelius, Francis Bacon, Antonio Snider-Pellegrini, Benjamin Franklin, and others had noted earlier that the shapes of continents on either side of the Atlantic Ocean (most notably, Africa and South America) seem to fit together. The similarity of southern continent fossil faunae and some geological formations had led a small number of Southern hemisphere geologists to conjecture as early as 1900[citation needed] that all the continents had once been joined into a supercontinent known as Pangaea. Frank Bursley Taylor suggested that the continents were dragged towards the equator by increased lunar gravity during the Cretaceous, thus forming the Himalaya and Alps on the southern faces.

Alfred Wegener was the first to formally publish the hypothesis that the continents had somehow "drifted" apart. However, he was unable to provide a convincing explanation for the physical processes which might have caused this drift. His suggestion that the continents had been pulled apart by the centrifugal pseudoforce of the Earth's rotation was considered unrealistic by the scientific community.[2]

The hypothesis received support through the controversial years from South African geologist Alexander Du Toit as well as from Arthur Holmes. The idea of continental drift did not become widely accepted even as theory until the late 1950s. By the 1960s, geological research conducted by Robert S. Dietz, Bruce Heezen, and Harry Hess, along with a rekindling of the theory including a mechanism by J. Tuzo Wilson led to widespread acceptance of the theory among geologists.

The hypothesis of continental drift became part of the larger theory of plate tectonics. This article deals mainly with the historical development of the continental drift hypothesis before 1950. See plate tectonics for information on current ideas underlying concepts of continental drift.

Answer 2

Alice has given you a very definitive answer and good sources for study, however I will try to give a basic understanding of the concept.

The center of the earth is molten and even rotates at a slower speed than the surface creating the Earths Magnetic Field.

If the hard surface above the molten part were solid the heat and activity of the interior would build up until there was a catastrophic explosion. Instead the heat and pressures escape in many locations resulting in volcano's and fissures creating the plates.

Since they are floating they will move due to the rotation and massive energy of the interior. If a plate is advancing in one direction it will recede on the opposite side creating the Sea Floor Spread. When two are pushing against each other it results in one riding over the top of the others creating mountains such as the Himalayan Mountains when the India Sub-Continent collided with the Eurasian Plate.

I hope this helps understanding the basics.

Answer 3

Most of the movement is from the earth trying to balance itself.

Answer 4

What exactly do you want to know? Some more info would be nice.