Oceanography - Lecture 1 Flashcards
Define: Bathymetry
The mapping and study of the ocean floor contours.
How did early scientist map the ocean floor?
Early scientists used a weighted line to measure the depth of the ocean floor.
What are the three common methods for bathymetry?
- Echo sounding
- Multibeam systems
- Satelite altimetry
How does echo sounding work?
Echo sounding uses pulses of sound energy (called: pings) to measure the depth of the ocean.
Why can echo sounding lead to inaccurate results?
Sound energy spreads out in a cone shape, and therefor as the ocean gets deeper the sound energy reflects off a greater surface area. Echo sounding relies on the first sound of the returning echo to sense depth which means it will only measure the most shallow point of the entire cone.
What is a multibean system?
A combination of many echo sounders to provide more accurate measurements for bathymetry.
What size arc does a multibean system cover? and how often does it send ‘pings’?
A multibean system covers a 120 deg arc, and sends a ‘ping’ every 10 seconds.
What are the drawbacks to using echo sounding or a multibeam system?
Both echo sounding and multibeam systems can prove to be time consuming, often leading to results that it is unknown whether the differences are temporal or spatial.
How accurate is Satelite altimetry?
Satelite altimetry can measure seas surface height from orbit with accuracy of upto 3cm
How does satelite altimetry work?
Satelite altimetry uses seas surface distortions(which can vary up to 200) to map the sea floor. These distortions occur when the gravitational attraction of a feature “pulls” water towards itself from the sides - forming a mound of water.
What is a continental margin?
The submerged outer edge of a continent.
What is a Ocean Basin?
The deep sea floor beyone the continental margin.
What is a Passive Margin?
A sub-category of continental margin which faces the edges of diverging tectonic plates. Also referred to as Atlantic type.
What is an Active Margin?
A sub-category of continental margin which is located near converging plates. Also referred to as Pacific type.
What are the components of a Continental shelf?
Shelf - Shallow, submerged edge of continent.
Slopes - Transition between shelf and deep ocean floor.
Break - Abrupt transition between shelf and slope.
Rises - Accumulated sediment at base of slope.
What are some features of deep ocean basins?
Oceanic ridges - an actively spreading center of ocean. hydrothermal cents abyssal plains seamounts trenches and island arcs.
