ocean basins Flashcards
what is bathymetry
The discovery and study of ocean floor topography
what is Isobaths
Lines of equal depth below a body of water
what marks the true edge of the continent
The transition to basalt from granite
the two parts The ocean floor divided into
- The continental margin: the submerged outer edge of a continent - can be active or passive
- The ocean basin: the deep-sea floor beyond the continental margin
4 parts of the continental margin
- continental shelf
- shelf break
- continental slope
- continental rise
whats the continental shelf
submerged extension of a continent
- width of the shelf determined by marine processes (e.g. currents) + proximity to a plate boundary
whats the shelf break
the abrupt transition from continental shelf to continental slope
- Water depth at shelf break remarkably constant ~140m worldwide (some exceptions)
whats the continental slope
the transition between the gently descending continental shelf and the deep-ocean floor - Inclination is typically ~70m per km
whats the continental rise
covered in layer of sediment, mostly transported into area by turbidity currents -Width ~ 100 to 1,000 km
what are turbidity currents
Local landslides triggered by earthquakes cause an abrasive underwater avalanche of sediments - Sediment filled water is denser than surrounding water - move at ~17 mph
how does topography of the ocean floor differ
with location
- The topography of deep-ocean basins different from that of the continental margin
what are oceanic ridges
underwater mountain ranges formed by tectonic activity at divergent plate boundaries, where new oceanic crust is created as plates pull apart
Ocean ridge system characteristics
- stretch ~65,000km around Earth
- Often devoid of sediment, rise ~2km above seafloor
- In some places, project above surface to form islands (Iceland, Azores, Easter Island…)
- Although typically called mid-ocean ridges, less than 60% actually exist along centers of ocean basins
- Spreading Rate Controls Topography
- Transform Faults and Fracture Zones Along an Oceanic Ridge
- Hydrothermal Vent Field along the Mid-Atlantic Ridge
how are Hydrothermal Vents formed
result from hot, mineral-rich water that came in close proximity to a magma source while under the seabed and then came into contact with cold ocean water as it emerged from the seafloor
what are Abyssal Plains
flat, featureless expanses of sediment-covered ocean floor found on the periphery of all oceans
- Found between continental margins and mid-ocean ridges
