GEO Chapter 2
Why was the man who first advocated the idea of continental drift scoffed at by geoscientists in the 1920s?
He could not provide a mechanism to move the continents or show that they were moving.
A hot spot track is formed by the periodic eruption of material from a mantle hot spot through a plate that is migrating over the Earth's surface.
True
Black smokers are undersea springs of hot water rich in mineral precipitate
True
Continental margins that coincide with plate boundaries are termed active margins.
True
Earthquakes are generated when rock moves along faults
True
Earthquakes are the best geologic marker for the three types of plate boundaries.
True
The most abundant rock in both continental and oceanic lithosphere is peridotite.
True
Which of these was NOT a line of evidence for the original proposal of the supercontinent Pangaea?
radiometric age-dating of similar types of rocks on several continents
Which of the following statements about Earth's magnetic field is FALSE?
The north and south magnetic poles slowly migrate from one polar region to the other, moving almost steadily from polar region, subtropical regions, and across the equator, and continuing steadily toward the other pole.
The angle of the Earth's magnetic field down into the ground toward the North magnetic pole is called the
inclination.
Who was Alfred Wegener?
the first geoscientist to provide geologic observations supporting a vastly different past arrangement of the continents
What is paleomagnetism?
the magnetic inclination and declination imprinted on a rock at the time of its formation
The variability in the depths of oceans and seas is called
bathymetry.
Identify the TRUE statement: A chain of seamounts and a mid-ocean ridge
both are volcanic in origin.
Which of these is not relevant to understanding how the nearly symmetric patterns of marine magnetic anomalies form at mid-ocean ridges?
discovering the anomalous heat flow at mid-ocean ridges in comparison to abyssal plains
Which of the following key methods for identifying both plate boundaries and the relative motions of plates did not exist in the early 1960s?
global positioning system (GPS) data
What are the average depths below the ocean surface to the abyssal plains and the mid-ocean ridges, respectively?
4.5 km and 2.5 km
An accretionary prism forms where magma from rising mantle material solidified beneath each side of a mid-ocean ridge.
False
Because the majority of Earth's crust is oceanic, the oldest crustal rocks will likely be igneous rocks of the sea floor.
False
Lithosphere and crust are synonymous.
False
Lithosphere can be both created and destroyed at transform-plate boundaries.
False
Lithosphere is recycled into the mantle at divergent-plate boundaries.
False
Oceanic lithosphere extends further down into the mantle than continental lithosphere.
False
Oceanic lithosphere subducts because it is thinner than continental lithosphere.
False
Paleomagnetism as well as the behavior of compasses and lodestones are due to the Van Allen radiation belts.
False
Scientists believe that Earth has sometimes had two or more north magnetic poles, based upon the differing paleomagnetic history (records of polar wander) of each continent.
False
The Moho separates the lithosphere from the asthenosphere.
False
The highest portions of the mid-ocean ridges are the center of the ridges.
False
The lithosphere-asthenosphere boundary is defined by pressure
False
The majority of undersea mountains are comprised of seamounts
False
Transform-plate boundaries are found only between segments of mid-ocean ridges.
False
Volcanic island arcs form on continental crust, inboard from subduction zones.
False
he major tectonic plates are nearly all the same size
False
Why were the apparent histories of polar wander later discarded as nearly meaningless?
No single reference point or area could be relied upon as having remained in the same place on the planet's surface.
Magnetic declination is the angle between true north and the direction along the Earth's surface in which a compass needle points.
True
Mantle rock becomes soft enough to flow at about 1,280°C
True
Oceanic lithosphere is thicker the farther one is away from a mid-ocean ridge.
True
The Himalayas and the U.S.'s Basin and Range province represent regions of convergence and rifting within continental lithosphere, respectively
True
The regions of sea floor that are relatively flat-lying, adjoin the continents, and are no deeper than approximately ½ km (500 m) are the continental shelves.
True
Identify the TRUE statement: Mid-ocean ridges
have higher geothermal gradients compared to most other areas of oceanic crust.
Which of the following is a key feature of ocean bathymetry but NOT a key feature of plate tectonics?
an abyssal plain