How Did Continental Drift Explain Glacial Deposits in Unusual Places?
What did the overall directions of glacial movement make more sense when the continents were pieced back together into?
A larger, ancient continent.
What is the Mid-Atlantic Ridge?
A long submarine mountain belt in the middle of the Atlantic Ocean.
What would have made the hypothesis of continental drift more widely accepted?
A proposed viable mechanism for how continents could move.
What did the process of seafloor spreading rekindle interest in?
Alfred Wegener's idea of continental drift.
What is the rounded outcrop in South Africa with a polished and scratched surface?
An outcrop with features similar to those observed at the bases of modern glaciers.
How did continental drift explain glacial deposits in unusual places?
By suggesting that the continents were once pieced back together into a larger, ancient continent.
Why was Wegener's mechanism of continent movement not feasible?
Continental crust is not strong enough to survive the necessary forces.
What are the blue arrows indicating?
Direction or movement indicated by the blue arrows.
What evidence puzzled geoscientists studying continents in the Southern Hemisphere?
Evidence of ancient glaciers near the equator.
Who were the geologists familiar with Wegener's work?
Harry Hess and Robert Dietz.
Who were the geologists who examined the new data on ocean depths and magnetism of the seafloor?
Harry Hess and Robert Dietz.
What weakness did Wegener's hypothesis of continental drift have?
It couldn't explain how or why the continents moved.
Why were geoscientists in the Southern Hemisphere intrigued by the idea of continental drift?
It explained observed similarities in rocks, fossils, and geologic structures across oceans.
What was the initial reaction of geoscientists to the hypothesis of continental drift?
Mixed reviews.
What new information in the late 1950s led to the reemergence of the idea of drifting continents?
New information about the topography, age, and magnetism of the seafloor.
How did Wegener imagine continents moved?
Plowing through or over oceanic crust.
What evidence supports the idea of glacial movement across an area about 280 million years ago?
Sedimentary rocks above the polished surface containing an unsorted collection of rocks of various sizes, scratch marks (striations) on the polished bedrock surface.
Where was the polar ice cap centered over 280 million years ago?
South Africa and Antarctica.
What did Hess and Dietz propose based on the new data on ocean depths and magnetism of the seafloor?
That oceanic crust was spreading apart at underwater mountain belts, carrying the continents apart.
What did Hess and Dietz propose based on their examination of the data?
That oceanic crust was spreading apart at underwater mountain belts, carrying the continents apart.
What did the magnetic data acquired during World War II show?
That the ocean floor had long submarine mountain belts, such as the Mid-Atlantic Ridge.
What did the magnetic data acquired during World War II show for the first time?
That the ocean floor had long submarine mountain belts.
What did Wegener discover about the overall directions of glacial movement?
That they seemed to come from the oceans, something that is not seen today.
What do the scratch marks on the bedrock surface tell geoscientists?
The direction that glaciers moved across the land as they gouged the bedrock.
What is seafloor spreading?
The process of oceanic crust spreading apart at underwater mountain belts.
What did the availability of new information about the topography, age, and magnetism of the seafloor lead to?
The reemergence of the idea of drifting continents.
What did Wegener's hypothesis of continental drift morph into?
The theory of plate tectonics.
What is the theory that Wegener's hypothesis of continental drift morphed into?
The theory of plate tectonics.
What is continental drift?
The theory that continents have moved and are still moving across the Earth's surface.
Why did scientists of Wegener's time abandon the hypothesis of continental drift?
They could demonstrate that Wegener's mechanism was unlikely.
Why were geoscientists in the Northern Hemisphere more skeptical of continental drift?
They had not seen the Southern Hemisphere data.