Grade 6/earth Science Chapter 3 Lesson 2

Front 1

mid-ocean ridge

Back 1

long chains of mountains that rise up from the ocean floor

Front 2

sonar

Back 2

using sound waves to measure the distance to an object

Front 3

sea-floor spreading

Back 3

adds more crust to the ocean floor and older strips of rock move outward from either side of the ridge

Front 4

evidence from ocean material

Back 4

rocks shaped like pillows from the central valley of a mid-ocean ridge

Front 5

evidence from magnetic stripes

Back 5

molten material that erupted and hardened while Earth's magnetic poles did not change that match those on opposite sides of the mid-ocean ridge

Front 6

evidence from drilling samples

Back 6

rock samples farther from the mid-ocean ridge are older and those closer to it are younger

Front 7

deep-ocean trench

Back 7

deep under water canyons

Front 8

subduction

Back 8

process by which the ocean floor sinks beneath a deep-ocean trench and back into the mantle