68 views11 pages
4 Apr 2011
School
Course
Professor
Chapter 2
PLATE TECTONICS
What is Plate Tectonics?
-tectonics: the study of the origin and arrangement of the broad structural features of the
Earths surface, including not only folds and faults, but mountain ranges, continents, &
earthquake belts
-plate tectonics: the earths surface is divided into several large, thick plates that move
slowly and change in size; intense geologic activity occurs at plate boundaries
-concept was developed in the late 1960s by combining continental drift & sea floor
spreading theories
-continental drift: idea that continents move freely over earths surface, changing their
positions relative to each other
-sea floor spreading: idea that the sea floor forms at the crest of mid- oceanic ridges, then
moves horizontally away from the ridge crest toward an oceanic trench
How Did the Plate Tectonics Theory Evolve?
The Early Case for Continental Drift
-ideas been around for 130 years
-Alfred Wegener
-noted in early 1900s that SA, Africa, India, Antarctica, & Australia all had almost identical
Paleozoic rocks & fossils
Scepticism About Continental Drift
-people didnt believe Wegener at first because they thought that rocks were much too
strong to be able to move about and crumple mountains, etc
www.notesolution.com
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 11 pages and 3 million more documents.

Already have an account? Log in
-the driving mechanism he proposed was a combination of centrifugal forces that causes
tides
-therefore in the northern hemisphere, they didnt believe him because they thought the
force wasnt strong enough
-more support in the southern hemisphere where the rocks were matching other places
Renewed Interest in Continental Drift
-because of 1) study of the sea floor & 2) geo research in relation to rock magnetism
Study of the Sea Floor
-oceans cover more than 70% of earth
-rock dredge: rocks are taken from sea floor by being broken off by a dredge, an open steel
container dragged along
-corer: used to sample sediments from the sea floor
-single- beam echo sounder: measures water depth & draws profiles of submarine
topography
-sidescan sonar: measures the intensity of sound reflected back to the tow vehicle from the
ocean floor and provides detailed images of the sea floor & info about bedforms & sediments
-seismic reflection profiler: works on pretty much same as above but uses a louder noise @
lower frequency
Geophysical Research
-inclination of the magnetic alignment preserved in the magnetite minerals in the lava
flows can be used to determine the paleolatitude at which the flow formed
-paleomagnetism: study of ancient magnetic fields
-polar wanderings are now used to reconstruct continental movement over time
www.notesolution.com
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 11 pages and 3 million more documents.

Already have an account? Log in
Recent Evidence for Continental Drift
-greatest evidence came from large rock formations that match each other on different
continents
-like SA & Africa
History of Continental Positions
-Pangea split up 200 million years ago
-continents have been in motion for the past 2 billion years
What is Sea Floor Spreading?
-Harold Hess
-he thought that the sea floor was spreading too, even though Wegener thought that the sea
floor stayed till while the continents moved about through them
-1962 sea floor spreading: the sea floor moves away from the mid- oceanic ridge as a result
of mantle convection
-spreading axis (spreading centre): the ridge crest, with sea floor moving away from it on
either side
-subduction: the sliding of the sea floor beneath a continent or island arc
-convection: circulation pattern driven by the rising of hot material & the sinking of cold
material
-hot material has a lower density so it rises, and cold material has a higher density so it
sinks
-Benioff zones of earthquakes: associated with trenches
-andesitic volcanism: forms volcanoes either on the edge of a continent or along an island
arc
How Old is the Sea Floor?
www.notesolution.com
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 11 pages and 3 million more documents.

Already have an account? Log in

Document Summary

Tectonics: the study of the origin and arrangement of the broad structural features of the. Earth"s surface, including not only folds and faults, but mountain ranges, continents, & earthquake belts. Plate tectonics: the earth"s surface is divided into several large, thick plates that move slowly and change in size; intense geologic activity occurs at plate boundaries. Concept was developed in the late 1960s by combining continental drift & sea floor spreading theories. Continental drift: idea that continents move freely over earth"s surface, changing their positions relative to each other. Sea floor spreading: idea that the sea floor forms at the crest of mid- oceanic ridges, then moves horizontally away from the ridge crest toward an oceanic trench. Noted in early 1900s that sa, africa, india, antarctica, & australia all had almost identical. People didn"t believe wegener at first because they thought that rocks were much too strong to be able to move about and crumple mountains, etc www. notesolution. com.

Get access

Grade+20% OFF
$8 USD/m$10 USD/m
Billed $96 USD annually
Grade+
Homework Help
Study Guides
Textbook Solutions
Class Notes
Textbook Notes
Booster Class
40 Verified Answers
Class+
$8 USD/m
Billed $96 USD annually
Class+
Homework Help
Study Guides
Textbook Solutions
Class Notes
Textbook Notes
Booster Class
30 Verified Answers