Ch 6b: Hydrosphere (Oceans) Flashcards
Oceans cover:
71% of Earth’s surface, uneven distribution.
Max depth of the ocean, average depth, volume of water
11km, 4.5km, 1.35x10^18
Ocean structure
Changing layers: fresh water influx, ocean size, more land exposure. Temperature, salinity, density
Ocean layer changes are more
noticeable at the surface and near coastlines.
Ocean water properties: Density
Variable and Temperature dependent, pycnocline.
Ocean water properties: Salinity
varies from 32-37%. Increases with depth, salinity is high where evaporation is high. Low where river water enters ocean
Temperature and Salinity with Depth
saline water is denser sinks
Halocline:
is region of rapid salinity change
Thermocline:
is zone of rapid temperature change
Ocean Temperature:
surface varies from 0 to 28degrees, still remains above 0 at depth. Lowest is 0.4 as salt doesn’t allow the water to freeze.
Ocean composition
relatively constant, proportions do not change but the amounts can change. Species maintain
Ocean movement: surface currents
Wind driven surface currents, 10% by volume. Caused by atmospheric circulation and Earth’s rotation. Affects upper 100m
Large scale movement: subsurface
Density driven subsurface currents, 90% by volume. Drives the thermohaline circulation
ENSO
El Nino -southern oscillation, occurs in the pacific ocean. Extreme ends are termed El Nino and La Nina
La Nina
lower pacific ocean temperature than normal
El Nino
higher pacific ocean temperature than normal
Coriolis Effect
Objects moving in a straight line appear to curve relative to observer on solid Earth
Coriolis Effect: Rotates about its vertical axis
CCW in Northern Hemisphere,
CW in Southern Hemisphere
Ekman Effect
Coriolis deflects wind driven currents in Northern hemisphere. Slightly CW of actual wind direction, deeper currents are progressively rotated CW. Overall average water movement is 90degrees CW of wind
Ekman Transport: Upwelling occurs…
where Ekman Transport is offshore
Ekman Transport: Downwelling occurs…
where Ekman transport is onshore
Geological Aspects
dominated by plate tectonics, sedimentation
Continental Margins
Type depends greatly on plate tectonic activity, type determines coastal shape and properties.
Continental Margins: Active Margin
occur along subduction zones or transform faults. Volcanically and tectonically active regions. Sediments of variable thickness. (terrigeneous, carbonates, volcanics)
Continental Margins: Passive Margin
Occur far from plate boundaries, flat lying, gentler gradients. Abundant shallow water sediments. (terrigeneous, carbonates)
Coastlines Modified by:
waves, tides, mass wasting events, uplift.
Coastlines are regions of
erosion and deposition
Waves created …
primarily by the friction between water and wind.
Larger waves are created by:
earthquakes, landslides, volcanic eruptions, extraterrestrial impacts
Wave depth is about
1.2 the wavelength
In deep water, the wave speed is
V = L/T
Wave strikes the beach at an angle, explain
Part of the wave nearest the shore hits the shallow water first and slows down, creates a bend in the wave and rest of the wave follows the bend
Longshore Transport is
a shallow water current, moves parallel to the shoreline. Caused by wave refraction. Controls depositional shoreline features and erosion and transport of sediment.
Tides are due to
gravitational pull of the sun and the moon.
Types of Tides:
Spring and Neap
Tides: Neap
low difference between low and high tides
Tides: Spring
big difference between low and high tides
Beaches are
gently sloping surfaces, washed over by waves, covered with sediment, deposition or erosion dominated, short-term and unstable features
Sea Level Changes are usually
local to regional in effect: tectonic uplife or subsidence, isostatic rebound, global warming, human causes
Sea Level ups and downs
Glaciation promotes drops and global warming promotes rises.
