Y1,S2 - Oceanography Flashcards
Name 3 types of Remote sensing?
-Ship-borne sonar and seismic surveys
-Passive satellite imagery
-Active satellite microwave altimetry and scattrerometry
What is ship-borne sonar and seismic surveys?
-‘Radar’ images using sound waves
-3 dimensonal picture of water density and ocean bottom rock structure
What is passive satellite imagery?
-Pictures formed from microwave and different coloured optical emissions
-Intensity of infra-red (heat) gives surface water temperature green colour of chlorophyll gives phytoplankton concentration
What is active satellite microwave altimetry and scatterometry?
-Satellite transmits microwaves pulse and recieves it reflected from the sea
-Pulse shape defines surface roughness so can deduce wave height and hence wind speed
-Detailed sea surface shape determines both ocean current speed and sea bottom topography
What are bathymetric profiles?
Depth profiles
What is a hypsographic curve?
A cumulative frequency curve showing the percentages of the Earth surfcae that le above, below or between any given levels
What is Ocean bathometry classifed by?
The slope and depth of the sea floor
What is the depth of the Abyssal plane?
~4.5km deep
What is the water depth of the MOR?
1.5-2.5km deep
How deep is the trench?
6-11Km deep
What is the height of the MOR?
2.5Km
What can be used as a proxy for ocean bathymetry?
Satellite altimetry
submarine canyons may appear on…
Continental shelves
What is Isostasy?
The proposition that at some depth under the ocean, the combined weight of overlying mantle, ocean crust and water is the same as the combines weight of mantle and continetla crust the sme depth under the continental crust the same depth under the continents.
What does an isostaic balance between oceanic and cotinental crust produce?
A 5km step at the Ocean basin edge
What would happen if the heat generated bynatural radioactivity in the Earths deep interior was not brought to the surface?
The mantle would melt
How is heat generated by natural radioactivity in the Earth transported?
By convection, which involves the flow of the transport of the underlying. mobile asthenosphere as well as transport of the overlying lithosphere
What forms at the axial ridge of a mid-ocean spreading centre when the asthenosphere cools?
The lithospheric plate
What continuosly replaces existing lithospheric plates?
New asthenosphere rising and cooling at the ridge axis; i then thickens as it moves away and cools.
How does the lithosphere change as it approaches he MOR axis?
The lithosphere is progressively younger, warmer and less dense. Its lower density makes it more elevated
What is Ocean crust generated by?
Partial melting of the upper mantle
What is the thickness of the ocean crust determined by?
The amount of melt, which in turn is determined by the temperature of the upper mantle
What is the normal upper mantle temperature?
1385C
What oceanic crust thickness does the normal upper mantle temperature produce?
Crustal thickness of 7km