Earth Science - Chapter 17
How are the convection currents set in motion?
Slab push and ridge pull
What evidence did Wegener use to estimate the time of Pangaea's break up?
Fossil data
Where do tectonic plates interact?
At plate boundaries
The supercontinent from Wegener's theory of continental drift is called __________
Pangaea
The tremendous amount of heat within Earth powers _________
Plate tectonics
An expedition finds a sample in the rock on the seafloor thought to be 4 million years old. What was the polarity of the Earth at that time, according to the figure?
Reversed
When a divergent plate boundary forms on continents, a __________ forms.
Rift valley
The geologic features on the ocean floor in this region resulted from _______
Rising convection currents in the magma
What is thought to be the driving mechanism of plate movement?
Convection currents in the mantle
According to the data shown in the figure, what was Earth's magnetic polarity like 5 million years ago?
The reverse of today
Much of Earth's internal heat comes from ___________________
The decay of radioactive elements
What is an isochron?
A line on a seafloor map tat connects points of equal age
What is the study of Earth's magnetic record?
Paleomagnetism
What causes the seafloor to spread?
Rising molten magma
Rocks close to mid-ocean ridges are __________ rocks far from mid-ocean ridges.
Younger than
Where are the youngest rocks on the seafloor located?
At the mid-ocean ridges
The subduction of an oceanic plate beneath a continental plate produces a(n) _________
Chain of volcanic mountains
Wegener proposed that the continents were __________
Formed at mid-ocean ridges
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
What is the polarity of a magnetic field that has the same polarity as the present magnetic field?
A normal polarity
According to the figure, where is an earthquake's focus most likely to occur?
Along the west coast of North America
What is the name of Alfred Wegener's hypothesis about moving landmasses?
Continental drift
Identify the subduction zone in the figure.
D (the figure has label D on it)
The map shows where the continents are likely to move in the next 50 million years. The shaded area represents their present position. According to the data on this map, what kind of boundary is found between the Americas and Africa?
Divergent
Places where two tectonic plates are moving away from each other are called __________.
Divergent boundaries
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 had moved
During the time of Pangaea, what had the greatest impact on Earth's climate?
It was a time of a giant global ocean
Which mineral may preserve magnetic patterns on the ocean floor which would help support tectonic plates?
Magnetite
__________ is a device that can detect changes in the strength of the magnetic field.
Magnetometer
What two topographic features of the ocean floor were discovered only with the use of sonar?
Mid-ocean ridges and deep-sea trenches
Harry Hess' theory of __________ explained how ocean crust is generated and destroyed.
Seafloor spreading
What is the process called when one plate is forced beneath another at a convergent plate boundary?
Subduction
The __________ states that Earth's crust and ridged upper mantle are broken into plates 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
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?
Very likely
