ELAJ+1-4

toc

Back To Home Page

Vocabulary

 * mid-ocean ridge** :the longest chain of mountains in the world
 * sonar** :the wave that scientists send down to see how long the mid-ocean ridge is
 * sea-floor spreading** :the process the continually adds new material to the ocean floor
 * deep-ocean trench** :an under water canyon
 * subduction** :is the process which the ocean floor sinks beneath a deep-ocean trench and back into the mantle

Mapping the Mid-ocean Ridge

 * use sonar
 * longest chain of mountains in the world

Evidence from Sea-floor Spreading

 * evidence from molten material,magnetic strips and drilling samples

Subduction at Deep-open Trenches
think of sea-floor spreading as a giant conveyor belt
 * the new oceanic crust is very hot

Subduction and Earth's Ocean

 * the ocean floor is renewed about every 200 million years
 * the pacific ocean is shrinking
 * the Atlantic ocean is growing