OCEANS: Practice 2
The fracture zone is a continuous linear feature of segments of active transform faults and _________.
"fossil" or inactive transform faults
The thickness of the oceanic lithosphere increases with age.
True.
Guyots (flat-topped seamounts) are the result of ________.
hot-spot volcanic islands being eroded after moving off their hot spot.
A major difference between the rigdge-push, slab-pull model and the convection model is the ridge-push, slab-pull model _____:
includes the decrease in elevation from the ridge to the rest of the plate as a factor
The age of the seafloor ______ away from the ocean spreading centers.
increases
When two oceanic plates converge, the plate with a greater density will subduct. This plate will partially melt causing the formation of a line of volcanoes on the overriding plate. This line of volcanoes is called a(n)
island arc
The mineral magnetite in basalt aligns itself with the ____ field of the Earth before the molten rock material cools past the Curie temperature.
magnetic
A continuous series of seamounts very close together formed from a hot spot near a spreading center is called a __________ ridge.
transverse
True or False: the thickness of the oceanic lithosphere increases with age.
true
The Himalaya Mountains are the result of a ______ convergence.
continent-continent
Tectonic plates move toward each other at ________ boundaries.
convergent
The Wadati-Benioff zone is the __________
dipping zone of seismicity at subduction zones.
New oceanic crust is created at some ________ boundaries as the plates move in opposite directions.
divergent
The boundaries of the tectonic plates can be outlined by plotting the locations of _________ on a map.
earthquakes
Paleomagnetism is the investigation of the __________
fossil magnetism in rocks (the world fossil" here does not refer to past life-forms.
A sunken rift zone is an example of a ___________
graben.
The pattern of heat flow near ocean ridges is _______
greatest near the ridge and generally decreases as you move outward from it.
The rate at which each oceanic plate (sea floor) moves away from the ridge is known as the _______
half spreading rate.
The two most important factors for determining if a rock will deform are ______
heat and pressure.
Match the later to its description:
Crust: The thinnest and outermost layer. Mantle: The thickest layer and middle layer Core: The inner layer and second in terms of thickness
Magnetic reversal are most likely associated with _______.
changes in the motion of material in Earth's liquid outer core.
Match the paleogeographic feature to its description.
1. Pangaea: A massive single land continent. 2. Panthalassa: A massive ocean covering most of the Earth (now the Pacific) 3. Gondwana: A supercontinent that contained the now Southern Hemisphere continents. 4. Laurasia: A supercontinent that contained the now Northern Hemisphere continents.
The characteristics listen below apply either to active or passive margins. Select all the characteristics of active margins:
1. Represents a plate boundary. 2. Modified by tectonic movement and volcanoes. 3. Ocean trenches possible
Select all the statements below that are true regarding seafloor spreading rates.
1. Spreading rates vary across the Earth in time. 2. The average spreading rate is about 5 cm per year.
Place the following plate tectonics events in order with the youngest (most recent) on top:
1. The Collision between India & Asia 2. Separation of Australia from Antarctica 3. Breakup of Pangaea to form Laurasia and Gondwana 4. Formation of the supercontinent Pangaea
Select the statements below that are true regarding polar reversals.
1. The magnetic fields appear to weaken before the reversal occurs. 2. After the reversal, the magnetic north and south poles have switched positions.
Match the type of convergent plate boundary to its description:
1: Ocean-ocean: This convergent boundary tends to form island arc volcanism as the subducting slab melts and the molten material rises up through the overriding plate. 2: Ocean-continent: The volcanoes formed here have an andesitic composition resulting from the mixing of granite and the basaltic magma from the subduction zone melting. 3. Continent-continent: This type of boundary forms after the complete closing of a ocean during other types of convergence.
The average seafloor spreading rate is between ______ per year
2-10 cm.
Select all the causes below why transform faults may occur.
Collisions between sections of the lithosphere, changes in speed and direction for plates as they move on a spherical surface, and variations in strength or location of convection cells in the Earth.
True or False: Since hot spots operate independently of the plate tectonic system, they are not useful for studying plate motion.
False.
True or False: The position of the north and south magnetic poles is constant over human time scales
False.
______ result in volcanic activity that may operate independently of plate boundaries. These volcanoes can form anywhere on a tectonic plate.
Hot spots.
A place where seafloor spreading at a mid-ocean ridge can be seen on land is________
Iceland.
Select all the evidence the Glomar Challenger provided to support the theory of seafloor spreading:
Sediment age and thickness increases outward from the ocean ridge system & no oceanic crust older than 180 million years was found.
The repeated opening and closing of ocean basins and the associated formation and breakup of super continents is known as the ________ cycle.
Wilson. Named after John Tuzo Wilson.
If a freely suspended magnet is pointing vertically downward with its north-seeking end, the magnet is likely
at the north magnetic pole
The existence of small ecosystems that can exist in sunlight-free areas by using microorganisms extracting stored chemical energy as the base of the food chain was discovered by studying ___________
black smokers at hydrothermal vents.
The majority of the earthquakes in the world occur at or near _____
boundaries of tectonic plates.
The difference between the full and half spreading rates is the half spreading rate is the rate at which __________
one plate moves away from the ridge, whereas the full spreading rate is the rate at which two plates move away from each other.
Island arcs form because a subducting tectonic plate ________
partially melts allowing molten magma to rise and produce a line of volcanoes.
Island arcs form because a subducting tectonic plate __________
partially melts allowing molten magma to rise and produce a line of volcanoes.
Basaltic magma that is extruded directly into ocean water tends to cool quickly into rounded flows called _______ basalts.
pillow
Each lithospheric __________ consists of the upper 80 to 100km of rigid mantle rock and is topped by either oceanic or continental crust.
plate
The theory of _______ _________ incorporates the ideas of both seafloor spreading and continental drift into a unified model.
plate tectonics
A polar _________ occurs when the north magnetic field and the south magnetic field switch orientations.
reversal
A ______ is a region on land where a new divergent boundary is forming due to extensional forces related to upwelling at the base of the continental crust and lithosphere.
rift zone.
The Glomar Challenger and later Joides Resolution were ______.
ships specifically constructed to obtain drill samples from the sea floor.
The Hawaiian Islands to the west of the main island have inactive volcanoes because they moved off of the hot _______.
spot. Hotspot.
A _______ zone is the area where tho continental plates collide after any associated oceanic crust has been subducted or scraped off the subducting slab.
suture
Plate _______ is the unified model that describes the fragmentation and movement of the lithosphere into 7 major plates and a number of small ones.
tectonics.
The rapid change in elevation across the sea floor at transform boundaries is caused by the differences in age and thus __________ of the different rock bodies.
temperature
Assuming a isostatic balance beforehand, what adjustment will occur if rock is removed from continental crust via erosion?
the continental crust will rise.
Basalt, the most common rock of the oceanic crust, can record the orientation of the magnetic field at the time of its formation because ________.
the magnetic mineral magnetite aligns itself with the Earth's magnetic field before the molten rock fully cools.
The Curie temperature is the temperature below which ________
the magnetic orientation of the rock's magnetic grains are locked in place.
Since the magnetic anomalies on either side of a spreading center can be matched up, and the age can be determined by using known magnetic reversals, the magnetic anomalies can be used to indicate ______.
the rate of seafloor spreading.
The s-wave shadow zone occurs at an angular distance greater than about 104 degrees from the location of the earthquake because _______
the waves are stopped by the liquid outer core.
Cores taken near the oceanic ridges show the age and thickness of the sediment increases as you move away from the ridge. This supports seafloor spreading because it indicates
the younger crust nearest the ridges has not been around long enough to accumulate the same thickness of sediment as sections farther out did
The _______ of oceanic lithosphere increase with a rate proportional to the square root of its age.
thickness
Convergent plate boundaries as where tectonic plates move _______ one another; _________ plate boundaries are where the plates slide past each other; divergent plate boundaries are where plates move away from each other.
toward; transform
Magnetic maps of the sea floor were made during the 1950s by ________.
towing marine magnetometers behind ships
Divergent boundaries are broken into sections and connected by _______ boundaries; these are the areas where the new crusts slide past one another.
transform
The San Andreas Fault in California is an example of a long _____ fault.
transform. It is a transform fault along the transform plate boundary formed between the North American and Pacific tectonic plates.