HEAT AND CONVECTION IN THE EARTH
Also remember that the lithosphere-asthenosphere boundary is really a gradual to a possibility of "Continental Shifting" in his lecture "On the Relation of Man to the Then there is the curious fact noticed by Lord Bacon, and though the. principal subsystems of Earth are the atmosphere, biosphere, they resemble | upiter (the Roman god was also called Jove), all have small .. section illustratingthe relationship between the lithosphere and the underlying asthenosphere. Notice how thin the crust of the Earth is in comparison to the other layers. The asthenosphere is the part of the mantle that flows and moves the plates of This flow is due to great temperature differences from the bottom to the top of the mantle. The Romans believed that the blacksmith god, Vulcan, used volcanoes as.
The temperatures may reach dgrees F. This is 3, times the air pressure on you at sea level!!!
Chapter 1 Plate Tectonics
Answer the following questions on a sheet of paper with your partner. If you need to look back to find the answers use the page titles located directly under the questions to help you.
When you finish the questions click on the Earth icon to return the program to the beginning. Name the four layers of the Earth in order from the outside to the center of the Earth.
What causes the mantle to "flow"? What are the two main metals that make up the outer and inner core? Describe in your own words how the Earth's layers were formed. Pangaea to the Present Lesson 2 The Earth is a dynamic or constantly changing planet. The thin, fragile plates slide very slowly on the 's upper layer. This sliding of the plates is caused by the mantle's convection currents slowly turning over and over.
This overturn is like a conveyor belt that moves the plates of the crust.
Chapter 1 Plate Tectonics
These plates are in constant motion causing earthquakes, mountain building, volcanism, the production of "new" crust and the destruction of "old" crust. When the subducting plate subducts at a shallow angle underneath a continent something called "flat-slab subduction"the subducting plate may have enough traction on the bottom of the continental plate to cause the upper plate to contract leading to folding, faulting, crustal thickening and mountain building.
This flat-slab subduction process is thought to be one of the main causes of mountain building and deformation in South America. Subduction angle[ edit ] Subduction typically occurs at a moderately steep angle right at the point of the convergent plate boundary. However, anomalous shallower angles of subduction are known to exist as well some that are extremely steep.
The relatively flat slab can extend for hundreds of kilometers. That is abnormal, as the dense slab typically sinks at a much steeper angle directly at the subduction zone. Because subduction of slabs to depth is necessary to drive subduction zone volcanism through the destabilization and dewatering of minerals and the resultant flux melting of the mantle wedgeflat-slab subduction can be invoked to explain volcanic gaps.
Flat-slab subduction is ongoing beneath part of the Andes causing segmentation of the Andean Volcanic Belt into four zones. Around Taitao Peninsula flat-slab subduction is attributed to the subduction of the Chile Risea spreading ridge.
Differences between the Earths’ Lithosphere and Asthenosphere
The most massive subduction zone earthquakes, so-called "megaquakes", have been found to occur in flat-slab subduction zones. The steepest dipping subduction zone lies in the Mariana Trenchwhich is also where the oceanic crust, of Jurassic age, is the oldest on Earth exempting ophiolites. Some milestones towards the acceptance of the Theory of Continental Drift Benjamin Franklin and Ralph Waldo Emerson were amongst the earliest pre-supposers of what we now accept as Continental Drift or Tectonic Plates theorising.
Benjamin Franklin spent some years as an american diplomatic representative in Paris. Such mining operations being undertaken in upland country and were above sea-level: Such changes in the superficial parts of the globe seemed to me unlikely to happen if the earth were solid to the centre.
I therefore imagined, that the internal parts might be a fluid more dense, and of greater specific gravity than any of the solids we are acquainted with, which, therefore, might swim in or upon that fluid. Thus the surface of the globe would be a shell capable of being broken and disordered by the violent movements of the fluid on which it rested. Ralph Waldo Emerson gave some consideration to a possibility of "Continental Shifting" in his lecture "On the Relation of Man to the Globe" delivered in Then there is the curious fact noticed by Lord Bacon, and though the inference might seem too daring, it is yet repeated by modern geologists, that the shape of the corresponding coasts of Africa and America would induce us to infer that the two continents of Africa and America were once united In fine, the conclusion at which in general geologists have arrived, is, that there had been repeated great convulsions of nature previous to the present order of things Whilst several notable observers had previously suggested that the continents on opposite sides of the Atlantic Ocean, most notably, Africa and South Americaseemed to be capable of fitting together, the hypothesis that the continents had once formed a single landmass, called Pangaea, before breaking apart and drifting to their present locations was first presented by Alfred Wegener to the German Geological Society on 6 January Although Wegener's theory was formed independently and was more complete than those of his predecessors, Wegener later credited a number of past authors with similar ideas.