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
•Tectonics is the study of the origin and arrangement of the broad structural features of
the earth’s 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 earth’s 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
•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.