Download Hydrology Study Guide

Hydrology Study Guide
Standard S6E3: Students will recognize the significant role of water in Earth processes.
Element S6E3.a: Explain that a large portion of Earth’s surface is water, consisting of oceans, rivers, lakes,
underground water, and ice.
 About 97% of Earth’s water is salt water stored in the oceans. About 3% is fresh water, consisting of lakes,
rivers, underground water, and ice. Less than 1% is usable water.
Element S6E3.b: Relate various atmospheric conditions to stages of the water cycle.
 In the water cycle, water evaporates from Earth’s surface into the atmosphere. The water vapor cools down
once it raises high in the atmosphere, condenses and forms into clouds, then falls back to Earth as
precipitation. Energy from the sun drives the water cycle.
 The water cycle renews Earth’s supply of fresh water. In the world as a whole, the rates of evaporation and
precipitation balance each other.
S6E3.c: Describe the composition, location, and subsurface topography of the world’s oceans.
 Sodium Chloride is the most abundant salt in ocean water.
 Salinity varies throughout the ocean, depending on the amount of evaporation or freezing, as well as the
addition of fresh water from rivers or precipitation.
 The oceans hold other dissolved salts. The concentration of all dissolved substances in sea water is about
3.5%, or 35 grams per 1 kilogram of water.
 The oceans also hold dissolved gases. Animals such as fish take in dissolved oxygen which they need to live
from the water. Sea plants, such as seaweeds, need the carbon dioxide that is dissolved in ocean water, to
survive.
 Technology, such as sonar, enables scientists to study the deep ocean floor despite the darkness, cold, and
extreme pressure.
 The ocean floor has features similar to those found on the continents, including continental shelves,
continental slopes, submarine canyons, abyssal plains, seamounts, the mid-ocean ridge, deep-sea
trenches.
 Below the ocean surface, the water is divided into layers by temperature, with uniformly cold temperatures in
deep water.
 Pressure increases greatly with increasing depth in the ocean.
 The Pacific Ocean is the largest and deepest ocean. It is located west of North America and South
America. It is east of the continents of Asia and Australia and north of the continent of Antarctica
 The Atlantic Ocean is the second largest ocean. It is located between the eastern coasts of North and South
America and the western coasts of Europe and Africa. Greenland and Iceland frame its northern end.
Antarctica cups its southern end.
 The Indian Ocean is the third largest ocean. It lies between the west coasts of Australia and the east coasts of
Africa, and to the south lies Antarctica.
S6E3.d: Explain the causes of waves, currents, and tides.
 Most waves are caused by winds blowing across the surface of the water.
 When waves enter shallow water, the wavelength shortens and wave height increases.
 Waves erode shorelines and break up rocks into pebbles and sand.
 The highest point of a wave is the crest.
 The horizontal distance between one crest and the next crest is called the wavelength.
 Waves are measured by their frequency, the number of waves that pass a point in a certain amount of time.











The lowest point in a wave is the trough.
The vertical distance from the crest to the trough is called the wave height.
Tides are caused by the interaction of Earth, the moon, and the sun.
There are two high tides and two low tides each day in most places.
The height of the tides during the month varies with changes in the positions of Earth, the moon, and the sun.
Twice a month, at the new moon and the full moon, the sun and moon are lined up. Their combined
gravitational pull produces the greatest range between high and low tide, called a spring tide.
In between spring tides, at the first and third quarters of the moon, the sun and moon pull at right angles to
each other. This line-up produces a neap tide, a tide with the least difference between low and high tide.
Currents are formed by Earth’s rotation, winds, and differences in water temperature.
The movement of warm-water and cold-water surface currents carries water around the world and
influences coastal climates.
Density differences between warm and cold water cause many deep-water currents in the ocean.
El Niño changes the pattern of winds and currents and affects Earth’s weather.