Plate Tectonics Flashcards
Define the Theory Continental Drift what was Pangaea made up of?
The Theory of Continental Drift states that the continents can move and that they were once connected in a supercontinent called Pangaea. Pangaea was made up of all of our continents that we know now.
What are 5 pieces of evidence for continental drift that Alfred Wegener had?
- Alfred Wegener found the same fossils on two sides of one ocean.
- Many layers of rock are similar to each other even though there are oceans between them.
- There were the same fossils in areas that don’t have similar climates, showing that at some point they had to be joined together and have the same climate.
- Coal forms were split in two different landmasses that are not remotely close to each other.
- There are a few glacial deposits in areas that don’t have as cold of climate for glacial deposits to form, and so this proves it had to once be connected to a country that does.
What two pieces of technology were developed later to help support and provide evidence for continental drift?
- The magnetometer can detect small changes in the magnetic fields above the ocean.
- Developments in sonar technology allowed us to measure the depth of the water.
These helped prove continental drift because they revealed that there are rifts and underwater mountains where plate boundaries are, proving that the continents can move.
How come Wegener’s hypothesis was rejected by other scientists?
Other scientists thought that there were two problems with Wegener’s theory:
- He couldn’t explain what forces caused the movement
- He couldn’t explain how the continents could move through the solid Earth.
Define Theory of Plate Tectonics
It describes how plate tectonics move and shape the Earth
Two pieces of evidence for plate tectonics?
SEAFLOOR SPREADING: Proves that because the oceanic crust is able to move away from itself, there has to be some sort of force behind it.
EARTHQUAKES: The ground moves because tension is suddenly releases in a plate boundary, causing it to shake
What are the layers of the Earth?
Crust, Mantle, Outer Core, Inner Core
What is the lithosphere? Asthenosphere? Mesosphere?
LITHOSPHERE: Located just below the crust
ASTHENOSPHERE: Just above the outer core
MESOSPHERE: Located in between the lithosphere and mesosphere
What causes the plates to move?
Convection currents in the mantle cause the plates to move. When the magma in the mantle churns, it heats and then cools again. As it does this, it is rising and falling, causing a churning motion. This motion carries the plates along with it, causing them to move.
Earth’s magnetic field has changed over time, once magnetometers had been invented, how did the magnetic data from the ocean floor help us?
The magnetometer detects the polarity of certain areas. It showed us that on either side of the mid-ocean ridge, the polarities were mirrored, showing that the plates spread outwards.
Isochron maps show the magnetic polarity as well as the age of the sea floor. Where is the sea floor the youngest and oldest.
Closest to the mid-ocean ridge is where the youngest bit is, and closest to the trench is where is oldest is.
What is the pattern of old oceanic floor and new oceanic floor as it relates to mid-ocean ridges in the middle of he Atlantic Ocean?
The mid-ocean ridge is where new crust is created, and as you move away from the ridge, the crust gets older and older.
What is the difference between oceanic and continental crust in terms of thickness, density, and composition?
Oceanic plates are denser and thicker than continental plates.
