Plate Tectonics
The geological creature on the ocean floor in this region resulted from__
Rising convection currents in the magma
What causes the seafloor to spread?
Rising molten magma
Harry Hess' Theory of ____ explained how ocean crust is created and destroyed.
Seafloor spreading
What is the process called when one plate is forced beneath another at a convergent plate boundary?
Subduction
How are the convection currents set in motion?
Slab push and ridge pull
Earthquakes focus point is most likely to occur
Along the west coast of North America
The subduction of an oceanic plate beneath a continental plate produces a ___
Chain of volcanic mountains
What was Earth's magnetic polarity like 5 million years ago?
Reverse of today
What was the polarity of the Earth 4 million years ago, according to the figure?
Reversed
Much of Earth's internal heat comes from___
The decay of radioactive elements
What two topographic features of the ocean floor were discovered only with the use of sonar?
mid-ocean ridges and deep-sea trenches
Places where two tectonic plates are moving away from each other are called ___
Divergent boundaries
When a divergent plate boundary forms on continents, a ___ forms
Rift valley
What is isochron?
A line on a seafloor map that connects points of equal age
What is the polarity of a magnetic field that has the same polarity as the present magnetic field?
A normal polarity
Where are the youngest rocks on the seafloor located?
At the mid-ocean ridges
What is the name of Alfred Wegener's hypothesis about moving landmasses?
Continental drift
What is the thought to be the driving mechanism for plate movement?
Convection currents in the mantle
Identify the subduction zone in the figure.
D
What boundary is between the Americas and Africa?
Divergent
Wegener proposed that continents were ____
Formed at mid-ocean ridges
What evidence did Wegener use to estimate the time of Pangaea's break up?
Fossil data
Which type of information was NOT collected by Wegener to support his continental drift? hypothesis?
Glacial deposits
What was one reason that Wegener's hypothesis of continental drift was rejected?
He could not explain where the continents has moved
During the time of Pangaea, what had the greatest impact on Earth's climate?
It was a time of a giant global ocean
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.
Less than
Which mineral may preserve magnetic patters on the floor which would help support tectonic plates?
Magnetite
A device that can detect changes in the strength of the magnetic field.
Magnetometer
What is the study of Earth's magnetic record?
Paleomagnetism
The super continent from Wegener's theory of continental drift is called ___
Pangaea
Where do tectonic plate interact?
Plate boundaries
The tremendous amount of heat within Earth powers
Plate tectonics
The ___ states that Earths crust and ridged upper mantle are broken into places that move at different rates and in different directions.
Theory of plate tectonics
A place where two plates slide laterally past each other is called a ___
Transform boundary
Probability that it came from a time when the magnetic field is the same as today.
Very likely
Rocks close to mid-ocean ridges are __ rocks far from mid-ocean ridges
Younger than