oceanography Flashcards Preview

Earth Science > oceanography > Flashcards

Flashcards in oceanography Deck (25):
1

general geography

71% of surface is ocean or marginal sea
south hemisphere mostly water

2

four main ocean basins

pacific-largest & greatest in depth
atlantic- half size of pacific & not as deep
indian- slightly smaller than atlantic; largely s. hemi body
arctic- 7% size of pacific

3

passive continental margin

not assoc w/ plate boundaries (Atlantic Coastline)
experience little volcanism
few earth quakes

4

active continental margin

ocean lithosphere subducted beneath continents
pacific rim
assoc with deep ocean trenches

5

passive

continental shelf
slope
cont rise
submarine canyons & turbidity currents
deep sea fan

6

continental shelf

flooded extension of continent
gently sloping from shoreline to deep ocean
thick accumulation of shallow water sediments
contains oil & important mineral deposits

7

continental slope

seaward edge of continental shelf
boundary btwn ocean & continental crust

8

continental rise

slope become more gradual incline
turbidity currents follows submarine canyon

9

submarine canyons & turbidity

deeps steep sided valleys cut into cont slope
some are seaward extensions of river valleys
most appear to be eroded away from turbidity currents

originate along cont slope
downslope movement of dense sediments- laden water
deposits are called turbidites
sediment deposit show graded bedding

10

deep sea fan

dense muddy currents emerge from the mouth of a canyon onto the relatively flat ocean floor
deposits form a fan

11

active

subduction
volcanic activity
continental slope descends into deep sea trench
accumulation of deformed sediments & scraps of ocean crust form accretionary wedges
may have little or no accumulation of sedimenets

12

deep ocean basins

trenches
abyssal plains
guyots
plateaus

13

trenches

long relatively narrow features
deepest parts of ocean
challenger deep, marianas: 11022 m
most located in pacific ocean
ocean lithosphere plunge into mantle
generates earthquakes
assoc with volcanic activity
pacific "ring of fire"
volcanic island arcs
continental volcanic arc

14

abyssal plains

likely the most level places on earth
sites of thick accumulation of sediments
found in all oceans

15

seamounts, guyots, and oceanic plateaus

seamounts- isolated volcanic peaks
many form near oceanic ridges, still volcanic activity and still grow
guyots- tablemounts , submerged flat top volcanoes, dormant, become flat top by wave action
oceanic plateaus- similar to continental flood basalt provinces

16

oceanic ridge system

70,000km long
crest stands 2-3km above adjacent ocean basin
divergent plate boundaries- new crust created

17

ocean ridge

broad features-not narrow as ridge would imply
1,000-4,000 kn wide
broken into segments 10-100s km long
segments separated by transform faults
consists of layers of newly transformed basalitc rocks

18

rift valleys

deep down faulted structures along ridge crest
50 km wide 2,000 m deep
volcanic cones common
rugged topography
similar to continental rift valley (E. Africa)

19

types of seafloor sediments

terrigenous
biogenous
hydrogenous

20

terrigenous sediment

material weathered from continental rock
fine particles remain suspended for long time
oxidation often produces red & brown colored sediments
deposition rate 1 cm/50,000 yrs
continental margin area

21

biogeneous sediment

shells, skeletons of marine animals & plants
most common: calcareous oozes produces from microscopic organisms
siliceous oozes- skeletons of diatoms & radiolarians
phosphate rich materials-bones, teeth and scales of fish, & other organisms

22

hydrogenous sediment

minerals that crystallize
most common type- manganese nodules, calcium carbonates, metal sulfides, evaporites
only small portion deposits in ocean

23

composition of sea water

consists of 3.5% dissolved minerals
avg. salinity is 35%
major constituents is sodium chloride

24

salinity

total amt of solid material dissolved in water
brackish-mix of fresh & sea water (estuaries &deltaic environ)
hypersaline- excessive salinity, avg 42% (Red Sea, Dead Sea, Great Salt Lake)
halocline- zone of rapid change in salinity btwn depths of 300-1000 m
low latitudes- low salinity
high latitudes- high salinity

25

process that affect salinity

low salinity- precipitation, runoff from land, iceberg melting, sea ice melting,
high salinity- evaporation, formation of sea ice