cross-section of the earth size:335 × 363 type:19kb jpg
TRANSCRIPT
Cross-section of the Earth
Size: 335 × 363 Type: 19KB JPG
The thin outside crust of the earth is the solid skin which covers the molten magma of the earth beneath. This magma moves in convection currents which cause rapid movement resulting in earthquakes, and the slower movement of tectonic plates which causes continental drift.
Size: 472 × 336 Type: 182KB JPG
If the magma is able to reach the earth’s surface because of a crack in the earth’s crust (hot spot) a volcano will be formed. This is how the islands of Hawaii were/are being formed. The Caribbean islands are also a result of this tectonic activity. The “Ring of Fire” is located above divisions between the plates where both earthquakes and volcanic activity are common.
PLATE TECTONICS
As mapping of the world advanced in the 1500’s with the exploration of North and South America, people noticed how the continents seemed to fit together like a jigsaw puzzle. The theory was that at one time all of the continents of the world were joined in a supercontinent known as PANGEA (see page 82).
Though scientists could not explain how this happened, over time more evidence was found to support the theory of continental drift. This included fossils of the same plants and animals found on different continents. Rock formations were also similar even though they were separated by oceans.
It was not until the 1960’s that advances in technology allowed for precise measurements of continental movement.
This supported the Theory of Continental Drift, by explaining that the Earth is covered by 20 “plates” which move as a result of movement in the hot flowing Magma below the plates. (page 84 in the Textbook)
