cchapter 15 plate tectonics: scientific revolution Flashcards
Who came up with the theory of continental drift?
Alfred Wegener
What did Wegener suggest?
A single supercontinent called pangea existed and then split up
Evidence for continental drift
-continental jigsaw puzzle
-Fossils match across the seas
-rock types and geological features
-Ancient Climates
name the 7 recognized plates
North American, South American, Pacific, African, Eurasian, Australian-Indian, and Antarctic plates.
the lithosphere vs the asthenosphere
The lithosphere is a rigid, relatively cool, and brittle outer layer of the Earth consisting of the crust and the uppermost part of the mantle. It is primarily composed of solid rock. as where the the asthenosphere lies beneath the lithosphere and extends to a depth of about 100 to 200 kilometers. It is a semi-fluid, ductile layer composed of partially molten rock or solid rock with high temperatures and pressures
along the axis of some ridge seg- ments is a deep down- faulted structure called a _______. This structure is evidence that tensional forces are actively pulling the ocean crust apart at the ridge crest.
rift valley
when boundaries diverge the lithosphere is stretched, causing the brittle crustal rocks to break into large slabs. As the tectonic forces continue to pull the crust apart, these crustal fragments sink, generating an elongated depression called a ______
continental rift
________ are the surface manifestations produced as oceanic litho- sphere descends into the mantle
Deep-ocean trenches
Subduction occurs because the density of the descending tectonic plate is _____ than the density of the underlying
greater
Typically, transform faults are part of prominent linear breaks in the seafloor known as __________, which include both the active transform faults as well as their inactive extensions into the plate interior
fracture zones
Testing the tectonic plate model evidences
-Ocean drilling (see that the thickness of sediments increase as you move away from the ridge crest formed s a result of spreading.
-hot spots ( as a result. of mantle plumes manifesting in the surface as a result of decompression melting)
-paleomagnetism (A study of rock magnetism conducted in Europe led to an interesting discovery. The magnetic alignment of iron-rich minerals in lava flows of different ages indicated that the position of the paleomagnetic poles had changed through time)
As the Pacific plate moved over the hot spot, a chain of volcanic structures known as a _______ was built
hot-spot track
During a ________ the north magnetic pole becomes the south magnetic pole, and vice versa. Lava solidifying during a period of reverse polarity will be magnetized with the polarity opposite that of volcanic rocks being formed today. When rocks exhibit the same magnetism as the present magnetic field, they are said to possess ________, whereas rocks exhibiting the opposite magnetism are said to have reverse polarity.
magnetic reversal, normal polarity, reverse polarity
magnetic surveys were accomplished by towing very sensitive instruments, called _______
magnetometers
As oceanic slabs sink into the asthenosphere, they “pull” the trailing plate along. This phenomenon, called _______, occurs because cold slabs of oceanic lithosphere are more dense than the underlying asthenosphere and hence “sink like a rock.
slab pull
