Sea-floor Spreading Science Bookworm

Continental crust is made up of ______________.

Granite

Why is the Pacific Ocean shrinking?

- The trenches are sucking up the crust faster than it can be made. -Sometimes a deep-ocean trench swallows more oceanic crust then a mid-ocean ridge can produce. -Then, if the ridge does not add new crust fast enough, the width of the ocean will shrink. -In the Pacific Ocean, subduction through the many trenches that ring the ocean occuring faster then the new crust can be added.

Sonar

-A device that bounces sound waves off underwater objects and then records the echos of the sound waves. -The time it takes for the echo to arrive, indicates the distance to the object.

Mid-Ocean Ridge

-An under water mountain range winding along all of the Earth's ocean floors. -It is where magma rises above the surface to create more rock.

What happens as subduction occurs?

-As subduction occurs, crust closer to a mid-ocean ridge moves away from the ridge and toward a deep-ocean trench. -Sea-floor spreading and subduction work together. - -They move the ocean floor as if it were on a giant conveyor belt.

deep-ocean trenches

-Deep underwater canyons. -They are located where the ocean floor plunges into a deep underwater canyon

What three types of evidence provided support for the theory of sea floor spreading?

-Eruptions of molten material -Magnetic stripes in the rock of the ocean floor -Ages of the rocks themselves.

Describe the process of sea-floor spreading.

-Sea-Floor Spreading begins at a mid-ocean ridge, which forms along a crack in the oceanic crust. 1. Along the ridge, molten material that forms several kilometers beneath the surface rises and erupts. 2. At the same time, older rock moves outward on both sides of the ridge. 3. As the molten material cools, it forms a strip of solid rock in the center of the ridge. 4. When more molten material flows into the crack it forms a new strip of rock.

Why is the Atlantic Ocean expanding?

-The crust is being made faster than it can be sucked up. -There are not enough deep ocean trenches. As a result the spreading ocean floor has virtually nowhere to go. -In most places the oceanic crust of the Atlantic is attached to the continental crust, so as the ocean floor spreads the continents around the crust move.

Why doesn't the Pacific Ocean keep getting wider?

-The ocean floor generally does not just keep spreading. -Instead, the ocean floor plunges into deep underwater canyons called deep-ocean trenches. -At a deep-ocean trench, the oceanic crust bends downward.

Geodynamo

-The process responsible for maintaining the Earth's magnetic field. -motion of the Earth's liquid outer core is converted into magnetic energy -The inner core is solid. -caused by convection and conduction currents in the fluid core.

sea-floor spreading

-The sea floor spreads apart along both sides of a mid-ocean ridge as new crust is added, carrying the continents along with them. -This process that continually adds new material to the ocean floor

Where would the densest oceanic crust be found?

-Under the deep ocean trenches. -New oceanic crust is hot. As it moves away from the mid-ocean ridge toward a deep ocean trench it cools and becomes more dense.

deep ocean trenches

-Underwater canyons when the oceanic crust bends downward. Formed by subduction of the oceanic crust underneath the continental crust. -

What scientist helped to discover the processs of sea-floor spreading?

An American geologist called Harry Hess discovered the process of sea-floor spreading.

What are the steps in the process of sea-floor spreading?

1. A long crack in the oceanic crust forms at a mid ocean ridge. 2. Molten material rises and erupts along the ridge. 3. Older rock moves outward on both sides of the ridge. 4. Molten material cools and forms a strip of solid rock in the center of the ridge. 5. As more molten material flows into the crack, a new strip of rock is formed.

How many miles does the mid ocean ridge cover?

50,000 miles

granite

A usually light colored igneous rock that is found in continental crust

Oceanic crust is primarily made of __________.

Basalt

convection currents

Circular currents in the mantle caused by the magma being heated by the core off the Earth. Cause electrons along the earth's core to move creating a giant magnet. Caused by changes in temperature and density of magma and earth. The fluids will expand and rise until they cool away from the source of heat. as the mantle material cools, it eventually stops rising. Warm magma goes up, Cool magma sinks back down towards core.

Why is the Pacific Ocean shrinking?

Deep ocean trench swallows more oceanic crust than a mid-ocean ridge can produce.

What happens at deep-ocean trenches?

In a process taking tens of millions of years, part of the ocean floor sinks back into the mantle at deep-ocean trenches.

What occurs at trenches?

In a process taking tens of millions of years, part of the ocean floor sinks back into the mantle at deep-ocean trenches.

How does new oceanic crust form?

It is formed when molten material erupts through the mid ocean ridge. This process is called sea-floor spreading

What is unique about Iceland?

It is located on an ocean ridge.

Why does oceanic crust go under the continental crust?

It is more dense.

What do magnetic stripes hold a record of?

Magnetic Stripes hold a record of the reversals of Earth's magnetic field.

Along what feature of the ocean floor does sea-floor spreading begin?

Mid-Ocean ridge

Why does the rock of the ocean floor have a pattern of magnetic stripes?

Molten iron cools as the iron lines up according to the poles of the Earth.

What device is used to map the ocean floor?

Sonar

How are magnetic stripes in the ocean floor evidence of sea-floor spreading?

Stripes of rock formed when Earth's magnetic field pointed north (normal) alternate with stripes of rock that formed when the magnetic field pointed south (reversed). The alternating pattern is the same on both sides of a mid-ocean ridge. -Gives a magnetic memory. -Rock formed during "normal" magnetic fields will have iron pointing in one direction, while rock formed during magnetic reversal will have iron pointing in the opposite direction.

What was the first research ship to do Sea-Floor Drilling?

The Glomar Challenger was the first research ship designed to drill samples of rock from the deep ocean floor.

What happens to the rock along the ridge when new molten material erupts?

The older rock moves outward on both sides of the ridge as new rock forms in the center of the ridge from the cooling of molten material. This process is sea floor spreading.

Where would you predict to find the oldest rock in the ocean floor?

The oldest rock will be furthest from the ocean ridge. Can be located in the deep ocean trenches.

What is subduction and where does it occur?

The process by which ocean floor sinks beneath a deep ocean trench and back into the mantle. The denser crust sinks back into the mantle.

subduction

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

Why does the rock of the ocean floor have a pattern of magnetic stripes?

The rock of the ocean floor contains iron. As molten material cooled and hardened, the iron bits inside lined up in the direction of Earth's magnetic poles, creating a pattern of magnetized stripes.

Magnetic Stripes

These are in the rock of the ocean floor show the direction of Earth's magnetic field at the time the rock hardened.

basalt

a dark, dense, igneous rock with fine texture in oceanic crust

What are the 3 types of evidence for sea-floor spreading?

Three types of evidence supported Hess's theory of sea-floor spreading: eruptions of molten material, magnetic stripes in the rock of the ocean floor, and the ages of the rocks themselves.