Chp.4) Plate Tectonics Flashcards
(___) proposed the first hypothesis of Continental drift in his 1915 book titled “The Origin of Continents and Oceans?
Alfred Wegener
this supercontinent began breaking apart 200 million years ago
Pangaea
true or false:
Wegener proposed that continents broke through ocean crust
True,
but this theory has been proven wrong
How did Wegener support his continental drift hypothesis? (3 items)
South America and Africa fit together like puzzle pieces
matching fossils in continents separated by the oceans
matching rock types and structure
what was the main objection to Wegener’s proposal?
inability to provide a mechanism for which continents moved
according to Wegener, gravitational forces of the Moon and Sun were capable of moving the continents
is this correct?
No
what is the largest tectonic plate
Pacific plate
All major interactions among plates occur along their
(___)
boundaries
in this plate boundary:
Continental rifts form at spreading centers within a continent
Divergent plate boundaries (constructive margins)
in this plate boundary:
Plates collide, an ocean trench forms, and lithosphere is
subducted into the mantle
Convergent plate boundaries (destructive margins)
in this plate boundary:
Plates slide past one another and no lithosphere is created or
destroyed
Transform plate boundaries
in this plate boundary:
– Two plates move apart.
– Mantle material upwells to create new seafloor.
– Ocean ridges and seafloor spreading
Divergent plate boundaries (constructive margins)
in Oceanic–continental convergence, which sinks into the asthenosphere, ocean or continental crust?
Oceanic because it is denser
in this type of convergence:
* Denser oceanic slab sinks into the asthenosphere.
* Pockets of magma develop and rise.
* Continental volcanic arcs form.
* Examples include the Andes, Cascades, and the Sierra Nevadan system.
Oceanic–continental convergence
in this type of convergence:
* Two oceanic slabs converge and one descends beneath the
other.
* Often forms volcanoes on the ocean floor.
* Volcanic island arcs form as volcanoes emerge from the sea.
* Examples include the Aleutian, Mariana, and Tonga islands.
Oceanic–oceanic convergence
this type of convergence can produce new mountain ranges such as the Himalayas
Continental–continental convergence
in this type of boundary:
Most join two segments of an oceanic ridge system along
breaks in the oceanic crust known as fracture zones
transform plate boundaries
(___) faults can also move ridge crests toward
subduction zones
transform
true or false
A few transform faults cut through continental crust
true
Examples include:
– The San Andreas Fault
– The Alpine Fault of New Zealand
true of false
Earth’s total surface area does not change
true
-Pangaea existed 200 million years ago
in 50 million years, Africa collides with (___), closing the Mediterranean and
initiating mountain-building
Eurasia
in 50 million years, Areas west of the (___) Fault slide northward past
the North American plate
San Andreas
Australia and new Guinea are on a collision course with
(___) in 50 million years
Asia
Some of the most convincing evidence confirming seafloor spreading has come from drilling directly into ocean-floor sediment and examining these 2 factors
- Age of deepest sediments
- Thickness of ocean-floor sediments verifies seafloor spreading
Hot spots and mantle plumes are caused by rising plumes of (___)
mantle material
volcanoes can form over (___) forming island chains like Hawaii
hot spots
Mantle plumes
* Long-lived structures
* Some originate at great depth, perhaps at the (___) boundary
mantle-core
what is probably the most persuasive evidence for the plate tectonics model
paleomagnetism
ancient magnetism is preserved in (___)
rocks
Paleomagnetic records show 2 forms of evidence that support plate tectonics
polar wandering (evidence that continents moved)
earth’s magnetic field reversal (recorded in rocks as they form at oceanic ridges)
what are 2 ways plate motion is measured
- By using hot-spot “tracks,” like those of the Hawaiian Island–Emperor Seamount chain, and the age of the seafloor
- Using space-age technology to directly measure the relative motion of plates
– Very Long Baseline Interferometry (VLBI)
– Global Positioning System (GPS)
true or false
By knowing the age of the seafloor and the distance from the spreading center, an average rate of plate motion can be calculated
true
true or false
No one model explains all facets of plate tectonics
true
what are the 2 factors of Slab-pull and ridge-push model for plate tectonics?
– Descending oceanic crust pulls the plate.
– Elevated ridge system pushes the plate.
one possible mechanism of plate tectonic motion is plate-mantle convection
in plate-mantle convection, mantle plumes extend from mantle-core boundary and cause
convection within the mantle
what 2 models support this?
– Whole-mantle convection
– “Layer Cake” Model
