Continental Drift Theory
What was the name of the supercontinent that contained all of Earth's continents?
Pangea
What is the name of the underwater mountain chain where new oceanic crust forms?
A mid-ocean ridge.
Which scientist developed the first complete statement of the continental drift hypothesis?
Alfred Wegener
What is a tectonic plate?
A large, irregular slab of solid rock that forms part of Earth's outer layer.
What is the continental drift theory?
The idea that Earth's continents were once joined together and later moved apart.
What happens to magma when it rises through a mid-ocean ridge?
It solidifies and forms new oceanic crust.
Which scientist discovered seafloor spreading in 1960?
Harry Hess.
What is the term for the process in which one tectonic plate moves beneath another and sinks into the mantle?
Subduction.
Scientists found the same types of fossils on continents that are now far apart. How does this support continental drift?
It suggests the continents were once connected, allowing the same plants or animals to live across them.
What happens to oceanic crust as it moves farther away from a mid-ocean ridge?
It cools, ages, and becomes denser.
Which invention uses sound waves to measure water depth and map the ocean floor?
Sonar.
What is radiometric dating used to determine?
The age of rocks and when geological events occurred.
Scientists found evidence of ancient glaciers in South America, Africa, India, Australia, and Antarctica. How does this evidence support the theory of continental drift?
The glacial deposits line up when the continents are placed together as Pangaea, suggesting the continents were once connected and later moved apart.
How do deep-sea trenches help balance the creation of new oceanic crust at mid-ocean ridges?
Deep-sea trenches are places where older oceanic crust sinks into the mantle through subduction, making room for newly formed crust.
What instrument detects small changes in magnetic fields and helped scientists study the ocean floor?
A magnetometer.
Scientists state that ocean-floor rocks are around 180 million years old, while some continental rocks are as old as 4 billion years. What does this difference suggest about oceanic crust?
Oceanic crust is continually formed and recycled, so it is generally much younger than continental crust.
Antarctica was once in a much warmer climate where plants could grow in warm, swampy environments.
Antarctica was once in a much warmer climate where plants could grow in warm, swampy environments.
Why do matching magnetic stripes appear on both sides of a mid-ocean ridge?
New rock forms on both sides of the ridge and records Earth's magnetic field as it cools, creating matching patterns as the seafloor spreads outward.
Which scientist proposed that earthquakes and floods had separated North and South America from Europe and Africa?
Abraham Ortelius.
Why did many scientists reject Alfred Wegener’s continental drift theory, and how did the discovery of seafloor spreading help support his idea?
Wegener could not explain what force moved the continents. Seafloor spreading provided an explanation by showing how continents could move over time.