Science 3

Convection Current

The movement of a fluid, caused by differences in temperature, that transfers heat from one part of the fluid to another.

New seafloor rock is continually being formed at mid-ocean rides, and old seafloor is continually being removed from Earths surface at ocean trenches. Rock on continents also is continually formed but is not removed. How then, would the age of the oldest rocks on the continents compare to the age of the oldest rocks on the seafloor?

The oldest continental rocks would be older that the oldest rocks on the sea floor.

In this model, what do the strips represent? What do the colors represent?

The strips represent the plates that make up the sea floor. The colors represents rocks of different age (or different magnetic patterns).

Wegener used evidence from climate change to further his theory.

An island in the Arctic Ocean contains fossils of tropical plants. According to Wegener, the island once must have been located close to the equator. Earths climate had not changed, instead the positions of the continents have moved.

Evidence from Magnetic Stripes

Earth behaves like a giant magnet, with a north pole and a south pole. Surprisingly, Earth's magnetic poles have reversed themselves many times during Earth's history. Scientists discovered that the rock that makes up the ocean floor lies in a pattern of magnetized "stripes." These stripes hold a record of reversals in Earth's magnetic field.

How does Hess's idea supports Wegeners theory of continental drift.

Evidence from Molten Material, Magnetic Stripes, and Drilling samples.

Evidence from Molten Material.

In a ridge's central valley, they found strange rocks shaped like pillows or like toothpaste squeezed from a tube. Such rocks form only when molten material hardens quickly after erupting under water. These rocks showed that molten material has erupted again and again along the mid-ocean ridge.

The "mountain" found in the Atlantic Ocean in 1855 was really part of what type of feature?

Mid-Atlantic Ridge.

Evidence for Seafloor Spreading is __________.

Molten Material, Magnetic Stripes, and Drilling Samples.

How does what is happening at slit B correspond to what happens where the seafloor is spreading and moving in opposite directions? What feature occurs at the corresponding location on the sea floor?

New "rock" (paper strips) is being added to the sea floor. The formation of new seafloor occurs, as does Mid-Ocean ridge.

What features on the seafloor are comparable to slits A and C? What is happening at slits A and C?

Ocean trenches are comparable to slits A and C. The old sea floor is sinking into Earths interior a slits A and C.

Why are organisms able to survive in the deep ocean near the East Pacific Rise?

Ocean water sinks through cracks, or vents, in the crust. The water is heated by contact with hot material from the mantle. The hot water then spurts back into the ocean.

Evidence from Drilling Samples

Scientists determined that samples from the seafloor that the farther away from a ridge the samples were taken, the older the rocks were. The youngest rocks were always in the center of the ridges. This showed that sea-floor spreading really has taken place.

Harry Hess thought that this happened at mid-ocean ridges.

Sea-floor spreading continually adds new material to the ocean floor.

Which process results in the formation of new oceanic crust?

Seafloor spreading

Is the Atlantic Ocean growing or shrinking? Is the Pacific Ocean staying the same size?

The Atlantic is growing as a result of seafloor being added along the mid-ocean ridge that runs its length. The Pacific is neither growing nor shrinking. Trenches located near South America, Alaska, and eastern Asia, are continually removing sea floor as new seafloor is being added along the Pacific's Mid-Ocean ridges.

If you were to sample and date the rocks along the colored strip starting at slit B and moving towards slit A, what change, if any, would you see in the age of rocks?

The age of the rocks would increase.

If you were to sample and date the rocks along the colored strip starting at slit B and moving towards slit C, what change if any, would you see in the age of rocks?

The age of the rocks would increase.

Density

The amount of mass in a given space; mass per unit volume.

Fossils also provided evidence to support Wegeners theory.

The fossils of the reptiles Mesosaurus and Lystrosaurus and a fern life plant called Glossopteris have been found on widely separated landmasses. This convinced Wegener that the continents have once been united.

Radiation

The transfer of energy through space.

Convection

The transfer of heat by movement of a fluid.

Conduction

The transfer of heat within a material or between materials that are touching.

Mountain ranges and other landforms provided evidence for continental drift.

Wegener noticed that when he pieced together maps of Africa and South America, a mountain range running from east to west in South Africa lines up with a range in Argentina. And European coal fields match up with cold fields in North America.