Lecture 3: Ocean Bathymetry and Seafloor Topography (i.e., How deep is the ocean and what does the seafloor look like?

Pelagic?

Describing organisms that live in the water column away from the ocean bottom.

Hypsographic Curve?

Graph of land elevation & ocean depth vs area.

Hadal?

Greatest depths of the ocean.

Shelf break?

The abrupt increase in slope at the junction between continental shelf and continental slope.

Echo Sounding?

(deptj recorder) instrument used to measure the depth of water by measuring the time interval between the release of a sound pulse & the return of its echo from the bottom.

Satellite altimeter?

- measures the variation in sea surface elevation, which is caused by gravitational attraction and mimics the shape of the seafloor

On average how deep is the ocean?

~12000

Active vs passive continental margin?

---Continental Margin-The edges of the landmasses below the ocean surface and the steep slopes that descend to the sea floor. ---Passive: are found where the continent-ocean transition is not a plate boundary. The transition from continental crust to oceanic crust occurs within a single plate. Passive margins have little seismic or volcanic activity and they tend to be relatively wide. They form after continents are rifted apart, creating a new and growing ocean basin between them. The continental margins in the Atlantic Ocean are of this type. ---- Active: are found where the continent-ocean transition is a plate boundary. In moving from continental crust to oceanic crust, you move from one tectonic plate to another. Active margins are often associated with earthquakes and volcanism and are often relatively narrow. Most active margins are associated with plate convergence and subduction of oceanic lithosphere beneath a continent, creating an ocean trench. EX Pacific Ocean

How do we map the depth of the ocean (i.e., bathymetry)?

-Hand line or wire marked with depth increments, with a lead weight (or rock) on the end but it is slow and inaccurate -Echo sounder / multibeam / side-scan sonar -Satellites

How many oceans are there? Can you label them on a map of the Earth?

5 oceans, Pacific, Indian, Atlantic, Southern

Describe the physical differences between active and passive continental margins?

Active:

What is the difference between the "Benthic" and "Pelagic" environments?

Benthic is the seafloor. Pelagic is water column.

Can you name a few oceanic ridges and rises found in the ocean?

Chile Rise Rio-Grande Rise -Atlantic ridge -Scotia Ridge

What is the deepest part of the ocean water column called? What is the shallowest?

Deepest: Hadal Shallow" Epipelagic

Turbidity current?

Dense, sediment-laden current flowing downward along an underwater slope.

Abyssal plain?

Flat ocean basin floor extending seaward from the base of the continental slope and continental rise.

Continental Rise?

Gentle slope

Seamount?

Isolated volcanic peak that rises at least 1000 m from the sea floor.

Littoral vs sublittoral?

Littoral: area of the shore between mean high water & mean low water; the inter-tidal zone. -Sub-littoral: benthic zone from the low-tide line to the seaward edge of the continental shelf; the sub-tidal zone.

Abyssal hill?

Low, rounded submarine hill less than 1000 m high

Bathypelagic?

Oceanic zone from 1000-4000 m

Mesopelagic?

Oceanic zone from 200-1000 m.

Abyssopelagic?

Oceanic zone from 4000 m to the deepest depths.

Benthic?

Of the sea floor, or pertaining to organisms living on or in the sea floor.

Bathyal?

Pertaining to ocean depths between approximately 1000 & 4000 m.

Abyssal?

Pertaining to the great depths of the ocean below approximately 4000 m.

Submarine canyons?

Relatively narrow, V-shaped, deep depression with steep slopes, the bottom of which grades continuously downward across the continental slope.

Continental Slope?

Relatively steep downward slope from the continental shelf break to depth.

Bathymetry?

Study mapping of seafloor elevations the variations of water depth; the topography of the sea floor.

Guyot?

Submerged, flat-topped seamount. Also known as tablemount.

Continental Shelf?

Zone bordering a continent, extending from the line of permanent immersion to the depth at which there is a marked or rather steep descent to the great depths. --nearly flat borders of varying widths that slope very gently away from the shoreline --- Width: 1500 km (930 mi)

Continental Margins?

Zone separating the continents from the deep-sea bottom, usually subdivided into shelf, slope, & rise.

Topography?

general elevation patter of the land surface or the ocean.

OCEANOGRAPHY?

the scientific study of the oceans and oceanic phenomena