Mid-Ocean Ridges - Geography Worksheets printable pdf download

Name:_______________________________________

Objective 1 Reading Guide – pages 141-147

Mid-Ocean Ridges

1. The East Pacific rise is just one of many ____________________ ridges that wind beneath Earth’s

_________________.

2. In the mid-1900s, scientists mapped the mid-ocean ridges by using __________________. Sonar is a device

that _____________ sound waves off underwater objects and then records the _______________ of these

sound waves.

3. Mid-ocean ridges curve like the seam of a baseball along the _____________________.

4. Most of the ___________________ in the mid-ocean ridge system lie hidden under hundreds of meter of

water. But in few places the ridge pokes above the ____________________.

5. The island of __________________ is part of the mid-ocean ridge that rises above the surface in the North

_______________Ocean.

6. A ______________-sided _________________ splits the top of some mid-ocean ridges.

What is Sea-Floor Spreading?

1. Harry Hess, an American __________________, was one of the scientists who studied mid-ocean ridges.

2. In 1960, _____________ proposed a radical idea. He suggested that a process he called sea-floor

________________ continually adds new material to the _____________ _____________.

3. In sea-floor spreading, the sea floor _______________ apart along both sides of the mid-ocean

_______________ as new crust is _____________. As a result, the _____________ floors move like conveyor

belts, carrying the ___________________ with them.

4. Sea-floor spreading __________________ at the mid-ocean ridge, which forms along a crack in the

_____________ crust.

5. Along the ridge, ___________________ material that forms several kilometers beneath the surface rises and

_____________. At the same time, ________________ rocks move outward on both side of the ridge. As the

molten material ___________, it forms a strip of solid ______________ in the ____________ of the ridge.

Evidence for Sea-Floor Spreading

Several types of evidence supported Hess’s _____________ of sea-floor spreading: __________________ of

molten material, magnetic stripes in the rock of the ocean floor, and the ________________ of the rocks

themselves.

Evidence from Molten Material

1. In the 1960s, scientists found evidence that ____________ material is indeed erupting along mid-ocean

ridges.

2. The scientists dived to the ocean floor in ______________, a small submarine built to withstand the crushing

_________________ four kilometers down in the ocean.

3. In the ridges central valley, Alvin’s crew found strange rocks shaped like _________________ or like

toothpaste squeezed from a tube. Such rocks form only when ________________ material hardens quickly

under ___________________.

Evidence from Magnetic Stripes

1. You read earlier that Earth behaves like a giant ______________, with a north pole and south pole.

2. Surprisingly, Earth’s magnetic poles have ________________ themselves many times during Earth’s history.

The last reversal happened 780,000 years ago.

Mid-Ocean Ridges - Geography Worksheets