Hydrology Study Guide
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Approximately 70% of the Earth’s surface is covered in water.
Ocean water (salt water) makes up 97% of the water of Earth.
Fresh water makes up 3% of the Earths water.
Fresh water comes from rivers, lakes, ice, underground water, stream, and
ponds.
Only about 1% of fresh water is accessible for human use. Most people get
fresh water from rivers and ground water.
The composition of the ocean’s water includes chlorine, sodium, sulfate,
magnesium, calcium, and potassium.
There are 5 major oceans on the Earth. They are in Pacific, Atlantic, Indian,
Southern, and Artic.
The general topography of the ocean floor includes basins, continental
shelves, continental slopes, abyssal plains, trenches, seamounts, and midocean ridges.
Salinity is a measure of the amount of dissolved salts in a given amount of
liquid. The average rate of salinity of the ocean is 3.5%. Warm, dry climates
have higher salinity while cooler, humid climates have lower salinity levels.
The structure of a wave includes a crest, trough, wavelength, amplitude
(wave height), and frequency.
Waves are formed from energy being transferred through water, usually by
wind.
The major ocean current (a movement of ocean water that follows a regular
pattern) types are surface currents, upwelling, and deep currents or density
currents.
Upwelling is beneficial to marine organisms because the nutrient-rich water
and the sun help ocean plants grow. Plankton thrive because they eat the
plants. The marine organisms live off of the plankton.
Surface currents are influences by Global winds, the Coriolos effect,
continental deflection, and temperature. Global winds blow across the Earth
creating currents. At the equator, they blow east to west. At the poles,
they blow west to east. The direction of surface currents is influenced by
the Coriolis Effect. Surface currents in the Northern Hemisphere turn
clockwise and counterclockwise in the Southern Hemisphere. When surface
currents meet continents, they change directions. The temperature of the
water can cause warm water currents or cold water currents.
 Tides are affected by both the sun and the moon, but the moon affects
tides more as it is closer to Earth.
 Tides are created from the moon’s gravitational pull on the ocean.
 Spring tides happen when the sun and moon are on the same side of the
earth (New Moon) or when the sun and moon are on opposite sides of the
earth (Full Moon).
 When the Moon is at first quarter or last quarter phase (meaning that it is
located at right angles to the Earth-Sun line), the Sun and Moon interfere
with each other in producing tidal bulges and tides are generally weaker;
these are called neap tides.
 Spring Tides
 Neap tides
 During a spring tide, the sun, moon, and earth form a straight line. During a
neap tide, the sun, the moon, and the Earth form a right angle, with Earth in
the middle.
 Be able to label the following: Continental Shelf, Continental Slope,
Continental Rise, Abyssal Plain, Seamounts, Trench, Mid-Ocean Ridge
Know the following vocabulary: Transpiration, topography, continental shelf,
Continental slope, abyssal plain, trench, crest, trough, wavelength, amplitude
(wave height), tides, upwelling, coriolis effect, surface currents, deep current,
spring tides, neap tides, evaporation, condensation, precipitation