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EESA06H3 (240)
Nick Eyles (207)
Chapter 2

Chapter 2 Notes (Beginning)

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Department
Environmental Science
Course Code
EESA06H3
Professor
Nick Eyles

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Chapter 2 – Plate Tectonics
What is Plate Tectonics?
Plate tectonic theory suggests that the surface of the earth is divided into several large
plates that change in position and size.
Intense geologic activity, such as volcanic eruptions and earthquakes occurs at plate
boundaries.
Tectonics is the study of the origin and arrangement of the broad structural features of
the earths surface, including not only fold and faults, but also mountain belts,
continents, and earthquake belts.
oExplains diverse features of the earth such as earthquake distribution, the origin
of mountain belts, the origin of sea floor topography, the distribution and
composition of volcanoes.
Concept of plate tectonics developed in the late 1960s, combining two pre-existing ideas
continental drift and sea floor spreading.
oContinental drift: continents moving freely over the earths surface, changing
their positions relative to one another.
oSea-floor spreading: a hypothesis that the sea floor forms at the crest of mid-
oceanic ridges, then moves horizontally away from the ridge crest toward an
oceanic trench. The two sides of the ridge are moving in opposite directions like
slow conveyor belts.
How did the plate tectonics theory evolve?
THE EARLY CASE OF CONTINENTAL DRIFT
Early 1900s Alfred Wegener, a German meteorologist made a strong case for continental
drift.
Noted that South America, Africa, India, Antarctica, and Australia had almost identical
late Paleozoic rocks and fossils.
Pangea reassembled the continents to form a giant super continent.
oStudied the similar rocks and fossils in the 5 continents
oOriginally separated by two parts, laurasia (which is now North America) and
Eurasia (excluding India). Gonwanaland was the southern supercontinent,
composed of all the present-day southern hemisphere continents and India
(which drifted north).
Late Paleozoic glaciations strongly supports the idea of Pangea
Paleoclimatology the study of ancient climates.
www.notesolution.com
oWegener reconstructed old climate zones. He discovered that paleoclimatic
reconstructions suggested that polar positions very different to those at present.
This could be interpreted as evidence for changes in the position of the poles over
time. However, hypothesized that this indicated the continents had moved and
gave strong support to this concept of continental drift.
SKEPTICISM ABOUT CONTINENTAL DRIFT
Wegener proposed that continents ploughed through the oceanic crust, perhaps
crumpling up mountain ranges on the leading edges of the continents where they pushed
against the sea floor. Most geologists thought that the idea violated what was known
about the strength of rocks at the time.
Careful calculations of these forces showed them to be too small to move continents 
combination of centrifugal force
RENEWED INTEREST IN CONTINENTAL DRIFT (NEW INVESTIGATIONS WERE IN
TWO AREAS: THE STUDY OF SEA FLOOR AND GEOPHYSICAL RESEARCH)
Study of the Sea Floor
Investing sea floors by samples of the rocks and sediments. Rocks can be broken from the
sea floor by a rock dredge, which is an open steel container dragged over the ocean
bottom at the end of a cable. Can be also sampled by a corer, a weighted steel pipe
dropped vertically onto the mud and sand.
Sea-floor drilling, Submersibles can take geologists to many parts of the sea floor to
observe, take pictures, and sample rock and sediments.
Single beam echo sounder indirect tool to study the sea floor. Measures water depth
and draws profiles of submarine topography.
oA sound signal sent down ward from a ship bounces off the sea floor and returns
to the ship. The water depth is determined from the time it takes the sound to
make the round trip.
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 and info about sediments
and bedforms.
Geophysical Research
Polar wandering: an apparent movement of the Earths poles.
ocame from the study of magnetism.
Wegeners work dealt with the wandering of the earths geographic poles of rotation. The
magnetic measurements show that the position of the magenetic poles moves from year
to year, but that the magnetic poles stay close to the gephoric poles are they move.
www.notesolution.com

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Description
Chapter 2 Plate Tectonics What is Plate Tectonics? Plate tectonic theory suggests that the surface of the earth is divided into several large plates that change in position and size. Intense geologic activity, such as volcanic eruptions and earthquakes occurs at plate boundaries. Tectonics is the study of the origin and arrangement of the broad structural features of the earths surface, including not only fold and faults, but also mountain belts, continents, and earthquake belts. o Explains diverse features of the earth such as earthquake distribution, the origin of mountain belts, the origin of sea floor topography, the distribution and composition of volcanoes. Concept of plate tectonics developed in the late 1960s, combining two pre-existing ideas continental drift and sea floor spreading. o Continental drift: continents moving freely over the earths surface, changing their positions relative to one another. o Sea-floor spreading: a hypothesis that the sea floor forms at the crest of mid- oceanic ridges, then moves horizontally away from the ridge crest toward an oceanic trench. The two sides of the ridge are moving in opposite directions like slow conveyor belts. How did the plate tectonics theory evolve? THE EARLY CASE OF CONTINENTAL DRIFT Early 1900s Alfred Wegener, a German meteorologist made a strong case for continental drift. Noted that South America, Africa, India, Antarctica, and Australia had almost identical late Paleozoic rocks and fossils. Pangea reassembled the continents to form a giant super continent. o Studied the similar rocks and fossils in the 5 continents o Originally separated by two parts, laurasia (which is now North America) and Eurasia (excluding India). Gonwanaland was the southern supercontinent, composed of all the present-day southern hemisphere continents and India (which drifted north). Late Paleozoic glaciations strongly supports the idea of Pangea Paleoclimatology the study of ancient climates. www.notesolution.com
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