Part Two II › Division III III › Section 231 231

Physical Features of the Earth’s Surface

Subject Outline

AVertical relief of the Earth's surface
- 1Hypsography of the Earth's surface: distribution of land and sea, elevation of the continents, coastlines
- 2Physiography of the continents: Europe, Asia, Africa, Australia, North America, South America, Antarctica
- 3The oceanic regions
  - aPrincipal oceanic features: continental margins, oceanic ridges, deep-sea trenches, and abyssal hills and plains [see C., D., and G., below, and 723.G.3.]
  - bOceanic physiography
BThe stable platform regions of the continents
- 1The continental shield areas and their age, structure, and constituent rocks [see also 214.B.4.b.]
- 2Uplift, downwarp, and fracture of continental platforms
  - aPlateaus and basins
  - bRift valleys
  - cWater bodies occupying fault-bounded structural depressions: lakes and landlocked seas; inland seas with outlets to the oceans; elongated seas formed by crustal separation
CThe continental shelf, slope, and rise
- 1Composition: evidence from bottom samples, geophysical techniques
- 2Structure and origin
- 3Submarine canyons incising the continental terrace
DThe oceanic deeps
- 1Components of ocean basins
  - aThe oceanic crust
  - bMajor features of the deep-ocean floor: oceanic ridges, aseismic ridges, trenches, fracture zones, and transform faults; seamounts and guyots; abyssal hills and plains; sediments of the ocean floor [see also G., below]
- 2The origin of ocean basins [see also 241.F.]
ECoral islands, coral reefs, and atolls [see also 354.B.2.]
FThe major mountain ranges and fracture zones of the Earth's crust on the continents and beneath the oceans
- 1Types of mountains; e.g., volcanic, block- fault, folded
- 2The worldwide system of mountain ranges, fracture zones, and volcanic island arcs
  - aThe Circum-Pacific System
  - bThe Tethyan System
  - cSubsidiary mountain ranges
  - dThe volcanic island arc systems
  - eThe rock types constituting the folded mountain ranges and island arcs [see 212.G. and 214.B.4.]
GOceanic ridges
- 1Classification of ridges
  - aThe global oceanic ridge system: spreading-centre zones and associated phenomena
  - bAseismic ridges
- 2Origin and growth of ridges
  - aGeneral geophysical properties
  - bOceanic ridges as manifestations of divergent lithospheric plate boundaries [see also 241.F.]