Oceanography
86 flashcards by MentisLibrary
Explore the ocean from the sunlit surface to the hadal trenches, covering currents, tides, waves, and seafloor geology. Includes ocean chemistry, the carbon cycle at sea, and the pressures reshaping marine life.
- What fraction of Earth's surface is ocean?
- About 71 percent
- What is the average depth of the ocean?
- About 3,700 meters
- What are the five named ocean basins?
- Pacific, Atlantic, Indian, Southern, and Arctic
- Which is the largest and deepest ocean?
- The Pacific Ocean
- What is average ocean salinity?
- About 35 parts per thousand, or 35 grams of dissolved salt per kilogram of seawater
- What are the two most abundant ions in seawater?
- Chloride and sodium
- What is the principle of constant proportions in seawater?
- The ratio of major dissolved ions stays nearly the same worldwide even where total salinity varies
- What processes increase surface salinity and which decrease it?
- Evaporation and sea ice formation increase it; precipitation, river inflow, and ice melt decrease it
- What is the typical pH of surface seawater?
- Slightly alkaline, around 8.1
- What is ocean acidification?
- The decrease in ocean pH caused by absorption of atmospheric carbon dioxide
- Why does the ocean act as a carbon sink?
- Carbon dioxide dissolves in seawater and is transported to depth by circulation and sinking organisms
- What is the biological pump?
- The transfer of carbon from the surface to the deep ocean by sinking organic particles
- What is the carbonate compensation depth?
- The depth below which calcium carbonate dissolves faster than it accumulates
- What is a thermocline?
- A layer where water temperature drops rapidly with depth
- What is a halocline?
- A layer of rapid change in salinity with depth
- What is a pycnocline?
- A layer of rapid density change with depth that resists vertical mixing
- What two properties control seawater density?
- Temperature and salinity, with pressure a minor factor
- What is the epipelagic zone?
- The sunlit surface layer from 0 to about 200 meters
- What is the mesopelagic zone?
- The twilight zone from about 200 to 1,000 meters, with light too dim for photosynthesis
- What is the bathypelagic zone?
- The midnight zone from about 1,000 to 4,000 meters, in total darkness
- What is the abyssopelagic zone?
- The zone from about 4,000 to 6,000 meters, covering most of the deep ocean floor
- What is the hadal zone?
- Water deeper than about 6,000 meters, confined to trenches
- What is the difference between the pelagic and benthic realms?
- Pelagic refers to the open water column; benthic refers to the seafloor and the organisms living on or in it
- What is the intertidal zone?
- The shoreline area between the highest and lowest tide levels
- What is the continental shelf?
- The gently sloping submerged edge of a continent, typically down to about 130 to 200 meters
- What is the continental slope?
- The steeper drop from the shelf break toward the deep ocean floor
- What is a continental rise?
- The gentle apron of accumulated sediment at the base of the continental slope
- What is a turbidity current?
- A fast, dense underwater flow of sediment-laden water down a slope
- What is an abyssal plain?
- A very flat region of deep ocean floor formed by sediment burying the underlying topography
- What is a mid-ocean ridge?
- An undersea mountain chain at a divergent plate boundary where new oceanic crust forms