PLATE TECTONICS PLATE TECTONICS
Continental Drift 194-195 • Alfred Wegener in 1915, in The Origin of Continents and Oceans , proposed that continents have drifted, a concept he called continental drift . He further proposed that all contintents had once fit together in a supercontinent he called Pan gaea (“all land”), 200 million years ago. • Today, the theory of plate tectonics encompasses with revisions , continental drift , explaining it in terms of motions of Earth’s crustal plates . • Plates include pieces of continents and of oceanic crust (all discussed later).
Continental Jig-Saw Puzzle 196-197 • “…the most immediately obvious evidence for plate tectonics is the fit of the continents.” • Additional evidence involves the fit of mountain ranges, and of fossil distributions, and reconstructions of ancient climates on different continents. See Continental margins (see next slide and Fig. 7.3 on p. 196) Rock types and mountain belts (red = metam.+ign 2 Gya; pink = deformed rock < 2 Gya) (also see next slide and text Fig. 7.6) Fossil distribution (see later slides and compare with Fig 7.4 on p. 197)
Fossil Matching Across the Sea Mesosaurus Compare with Fig 7.4 which appears to mislocate the mesosaurus fossil distribution. The map here is from USGS.
198 Match of orgogenic belts (see Fig 7.6 on page 198)
Paleoclimate – Ice Sheets Paleozoic Era – 300 mya 199 Compare with Fig 7.7 on page 199
Note arrows on maps showing glacier movement directions
Arrows on previous slide show movement direction inferred from glacial striations shown here
Crustal Plates 201 and Plate on 202-203 Their boundaries were initially inferred from maps of the distribution of earthquakes and volcanoes Earthquakes Volcanoes
Seismic Activity 1978-1987
Lithospheric Plates Compare with Fig. 7.10, pp. 202-203 (shown next) The major plates are numbered (see list in later slide)
See Fig. 7.10 in the text to discern all the details on this USGS map
Lithospheric Plates • 7 major plates: 1. North American 2. South American 3. Pacific 4. African 5. Eurasian 6. Australian-Indian 7. Antarctic • The plates include ocean floor and portions of continents ; the plates are not just continents. For example, the Atlantic Ocean is split into 4 pieces. See map in slide #8. • Motion – average 5 cm/yr . Each plate moves as an almost stable unit. Most interactions involve plate boundaries. • Complications – terranes (pieces of one plate accreted to another) & microplates .
You've reached the end of your free preview.
Want to read all 68 pages?
- Spring '16
- Plate Tectonics