Plate tectonics 2 Flashcards
Who proposed the theory of Continental Drift?
Alfred Wegener
Wegener suggested that continents were once connected as one large landmass called Pangea.
What does Pangaea mean?
All land
Pangaea was the name given to the supercontinent proposed by Wegener.
Approximately how many years ago did Wegener believe Pangaea broke apart?
200 million years ago
What was a major problem with Wegener’s theory of Continental Drift?
He could not explain how the continents moved.
What are the two major landmasses that formed after the first break of Pangaea?
Laurasia and Gondwanaland
List the continents that were part of Gondwanaland after its break.
- South America
- Africa
- India
- Australia
- Antarctica
What evidence did Wegener provide to support his theory of Continental Drift?
- Similarities in continental shape
- Same fossils found on different continents
- Same rock types found on different continents
- Evidence of ancient climates
- Volcanoes and earthquakes
What discovery was made in the 1950s regarding the ocean floor?
A mid-ocean ridge system exists that forms an underwater mountain range.
Who proposed the theory of sea floor spreading?
Harry Hess
What are the three parts of Harry Hess’s theory of sea floor spreading?
- Hot, less dense magma is forced upward at mid-ocean ridges
- Magma cools and hardens, forming mid-ocean ridges and pushing plates apart
- Magma flows sideways, carrying the seafloor away horizontally
What did scientists find regarding the age of the ocean floor in 1968?
Oldest rocks were 180 million years old; youngest rocks were at mid-ocean ridges.
What is the significance of iron minerals in rocks like basalt?
They act like tiny compass needles pointing toward magnetic north.
What phenomenon does the magnetic alignment in rocks indicate?
The Earth’s magnetic field has reversed itself many times.
What theory emerged from combining Wegener’s and Hess’s theories?
Plate Tectonics
What is the study of Plate Tectonics focused on?
The formation and movement of Earth’s lithospheric plates.
What are the two types of tectonic plates?
- Continental Plates
- Oceanic Plates
What are Continental Plates composed of?
Granite
Continental crust is less dense and thicker than oceanic crust.
What do Oceanic Plates consist of?
Basalt
Oceanic crust is more dense and thinner than continental crust.
What drives the movement of tectonic plates?
- Mantle Convection
- Ridge Push
- Slab Pull
Describe a convergent plate boundary.
Plates are moving together.
What is an example of a convergent boundary that involves subduction?
Andes Mountains in South America
Which mountain range is an example of a convergent collision boundary?
Himalaya Mountains
Name an example of a divergent boundary.
Mid-Atlantic Ridge
What is the San Andreas Fault an example of?
Transform boundary
What is a craton?
An ancient continental core
Where is the North American craton located?
Canadian Shield
What is a terrane?
A large landmass that has attached to another landmass, detected by different fossils, rocks, and faults.
What is an example of a terrane?
India
