Plate tectonics Flashcards
Explain the theory of plate tectonics.
Plate tectonic refers to a theory describing the internal forces that deform the earth’s crust. Plate tectonics links sea floor spreading, continental drift, earthquake activity, volcanic activity and mountain building.
What is a plate?
The theory of plate tectonics is based on a model of the earth in which the lithosphere is made up of several separate pieces known as plates, rather than a continuous shell.
How many major tectonic plates are there?
There are 7 major tectonic plates.
On which tectonic plate is Ireland located?
The Eurasian plate.
Who first proposed the theory of continental drift?
Alfred Wegener (a German meteorologist with an interest in geology)
When did Alfred Wegener first publish his theory of continental drift?
1912
List 3 proofs Wegener suggested as evidence of continental drift.
Continental fit
Matching fossils
Matching rocks and mountain ranges
What is continental fit and how does it help prove Wegener’s theory of continental drift?
Wegener argued that the shapes of the coastlines of the continents was part proof of this theory. (In the 1960s geophysicists used ocean floor maps to find an almost perfect match in the continental shelves of South America and Africa at a depth of almost 1000 metres.)
How does matching fossils help prove Wegener’s theory of continental drift?
Many paleontologists had agreed on the similarities of plant and animal fossils found in the southern continents. Many of these fossils were not to be found in the northern continents. Paleontologists suggest then land bridges had existed which would explain migration of plants and animals. No evidence of land bridges has been found. Wegener’s theory that the fossils were laid down in the one region prior to continental drift is now widely accepted.
How do matching rocks and mountain ranges help prove Wegener’s theory of continental drift?
Several mountain ranges end at the coastlines of continents. Many of them are of comparable age, of similar structure and of similar rock type. Ex. Appalachian mountains of the USA and the Caledonian mountains of Ireland, Britain and Scandinavia.
What causes tectonic plates to move?
Thermal convection currents cause plates to move.
The theory of thermal convection suggests hot, less dense material from within the earth rises slowly to the surface. As it does so, it flows sideways, cools and then, because cooling makes it more dense, sinks. As the material moves sideways it drags the lithosphere along with it.
List the 3 categories of plate margin.
Divergent plate margins
Convergent plate margins
Transform plate margins
What are divergent plate margins?
Divergent plate margins are plate boundaries in which plates move apart.
What are convergent plate margins?
Convergent plate margins are plate boundaries in which plates collide.
What are transform plate margins?
Transform plate margins are plate boundaries in which plates grind past one another.
