Wiki Page, A2:World Geography and Civilizations, term 1-1: Changes within the earth

Wiki Page
2013-10-21T08:01:13-06:00

core - center of the earth consisting of very hot metal, mainly iron mixed with some nickel.

mantle - around the core is a thick layer of rock.

crust - the rocky surface layer which is surprisingly thin.

lava - molten rock

fold - when rock layers bend and buckle the result is a fold.

faults - breaks in the earth's crust.

plate tectonics - the earth's outer shell is not one solid piece of rock. Instead, the lithosphere, the earth's crust and the brittle, upper layer of the mantle, is broken into a number of moving plates. The oceans and continents ride on top of these moving plates. Imagine a hard boiled egg with the thin shell cracked that can slide along the egg and run into other pieces of shell. It is along these faults and plate boundaries that most earthquakes and volcanoes occur.

Click on this Link to see where earthquakes are happening right now.

continental drift theory -

German explorer and Scientist named Alfred Wegener proposed the continental drift theory, which became widely accepted in the 1960s. He theorized that about 180 million years ago Pangaea began to break up into separate continents.

Wegener argued that the almost identical fossils of ancient animals and plants found in South America, Africa, India and Australia proved that these continents were once connected.

Seafloor Spreading- Scientists use sonar devices to map the floor of the Atlantic Ocean. They revealed that the ocean floor was not flat. Landforms on the ocean floor are very similar to those found on the continents (mts, canyons, wide plains). Ocean floor rocks are much younger than those on the continents. The youngest rocks were found by the underwater mountain chains. This theory says that molten rock from the mantle layer of the earth rises and breaks through the rift valley. The rock spreads like a conveyer belt out on both sides.

WHY did people doubt that these theories were true?

They questioned just HOW do the continents move.

What force is powerful enough to send gigantic plates sliding around the earth?

Scientists turn to Convection. Convection is a circular movement of heat coming up from the mantle. Heat energy.

ring of fire - a circle of volcanoes surrounding the Pacific Ocean. The ring includes the Cascades in North America, the islands of Japan and Indonesia, and the Andes in South America.