Science 17.2
Magnetic reversal
A __________ happens when the flow in the outer core changes, and Earth's magnetic field changes direction
Magnetometer
A device that can detect small changes in magnetic fields is called a(n) ________
The reverse of today
According to the data shown in the figure above, what was Earth's magnetic polarity like 5 million years ago? (hint: compare the colors to see direction)
True
Maps made from sonar and magnetometer data showed an ocean floor that had features, such as mountain ranges and trenches, that were bigger than anything found on land.
Paleomagnetism
The study of the history of Earth's magnetic field ________
Very likely
An expedition brings up a piece of rock from the Gauss normal epoch. According to the figure, what is the probability that it came from a time when the magnetic field is the same as today?
Isochron
An imaginary line on a map that shows points that have the same age is called a(n)
In seafloor spreading, new oceanic crust is added at the mid-ocean ridge, and as intrusion continues, seafloor moves towards the edge of the oceanic plate, where it is ultimately pulled back down into the magma below
Describe why seafloor spreading is like a moving conveyor belt? (2 points)
Sea floor spreading
Harry Hess' theory of _______ explained how ocean crust is generated and destroyed.
Younger
Rock samples taken from areas near ocean ridges were found to be ________ than samples taken from areas near deep-sea trenches.
Sea floor spreading
The theory that explains how new oceanic crust is formed at ocean ridges, slowly move away from ocean ridges, and destroyed at deep-sea trenches is called _____
Less than
The thickness of ocean sediments that are close to a mid-ocean ridge is _____ the thickness of ocean sediments that are far from mid-ocean ridges.
Oceanic crust
Which is younger?
Because Pacific is moving at a faster rate than Atlantic
Why are magnetic bands in the eastern Pacific Ocean so far apart compared to the magnetic bands along the mid-atlantic ridge?