PLATE TECTONICS (Reading 2)
- What are plate tectonics?
o Used to be called “continental drift”
o Involves creation & recycling of Earth’s crust
Tectonic & volcanic activity
o Continuous process; no beginning or end
- Why does it happen?
o Crust floating on the mantle
o Large convective currents flowing through the molten material
- How long has it been going on?
o Going on as long as the Earth has had a crust – 4 billion years
o Numerous agglomerations and dispersals of continental blocks
Latest “cycle”: breakup of Pangaea (250 MYBP)
- How do we know about the pattern and speed of the process?
- What are its impacts?
o Changes global geography by agglomeration & dispersal of continental masses
o Changes global topography by mountain building
o Extends major control on global climate on a range of time scales
Controls global carbon cycle (Earth’s Greenhouse Effect)
A. changes locations of continents
B. changes mass and topography
C. influences atmospheric chemistry
o Also influence climate through atmospheric chemistry & transparency
Most connected to volcanic activity (to effects of individual eruptions & long
term variations in intensity of global volcanism)
o N & S hemispheres have distinct biological differences NH more modern, SH more
Placentals, marsupials & monostremes
Gymnospers & angiosperms
Ratites (Emu, Kiwi, Ostrich, etc., other flightless birds)
Eucalyptus only in Oceania
o Distinctive biological impact of plate tectonics: related to islands’ flora and fauna
Islands mostly volcanic
Ex. Lonesome George, Flightless comorant
o Major control on global climate at range of time scales; size & character of carbon cycle
o Climate change constrained human evolution
o Controlled diffusion of people o