Water in Earth

1
Water in Earths Processes
2
groundwater
evaporation
water cycle
precipitation
condensation
Wordsplash
habitat
irrigation
water vapor
transpiration
photosynthesis
3
Lesson 10A Wet Planet

• EQ How is Earths water distributed among
  saltwater and freshwater?

4
How is Earths water distributed among saltwater
and freshwater

• Some people call Earth the blue planet because
  over 70 of Earths surface is covered with
  water.
• Most of Earths freshwater is found in the polar
  ice caps near the North and South Poles.
• From largest to smallest, the amounts of water on
  Earth are salt water (97), solid fresh water
  (2), liquid fresh water (1).

5
Salt Water

• Most of the water on Earth is in Earths oceans
• Oceans contain salt water.
• The salinity, or salt concentration, averages
  about 3.5, or 35 grams of salt per kg of water.
• In order of size from largest to smallest,
  Earths oceans are the Pacific, Atlantic, and
  Indian Oceans.

6
Fresh Water

• Most of the Earths freshwater is located in the
  polar caps.
• Lakes, rivers, streams, and glaciers hold the
  rest of Earths surface freshwater.
• A glacier is a very slow moving river of ice.
• A large portion of the rest of Earths freshwater
  is trapped between underground layers of rock.
  This trapped freshwater is called groundwater.

7
Quick Check

• About how much of Earths surface is covered by
  water?
• A. 0
• B. 30
• C. 70
• D. 100

8
Quick Check

• From the largest to smallest, the amounts of
  water on Earth are
• liquid fresh water, solid fresh water, salt
  water.
• B. salt water, solid fresh water, liquid fresh
  water.
• C. salt water, liquid fresh water, groundwater.
• D. groundwater, salt water, solid fresh water.

9
Quick Check

• A glacier is
• A. a river of liquid water.
• B. an ice cap.
• C. a solid lake.
• D. a slow river of ice.

10
Lesson 25 Sun, Wind, and Water

• EQ How does a drop of water move through the
  water cycle?

11
Wind

• Earth receives heat energy from the sun through
  Radiation.
• Radiation is the movement of energy through empty
  space.
• Air at different places on Earth heats up
  unevenly. The uneven heating up of Earths air
  is what produces wind.
• Cool air moves toward warmer air. Warm air moves
  away from cooler air. Moving air is wind.

12
Water

• Very little water is ever lost on Earth
• The sun is the source of energy that drives the
  water cycle.
• Energy from the sun causes the water particles to
  move faster and escape into the air as water
  vapor.

13
Water

• Water vapor rises into the air and cools down.
  The water molecules move slower and come closer
  together, or condense. This is called
  condensation.
• Condensation forms clouds and precipitation such
  as rain, sleet, hail, and snow.
• The precipitation falls to the ground and gathers
  there in puddles, ponds, rivers, lakes, and
  oceans. (Accumulation)
• Some water seeps into the ground and collects
  there. This underground water is called
  groundwater. (runoff)

14
Water

• Some groundwater finds its way into oceans.
• Water on the surface is warmed again by the sun
  and will evaporate. So will water in the soil.
• Water vapor also enters the air from plants.
  This is called transpiration.
• This keeps the water cycle going.

15
Quick Check

• What is the source of energy that produces winds
  and causes evaporation?
• A. lightning
• B. Earths rotation
• C. the moon
• D. the sun

16
Quick Check

• Heating liquid water produces
• A. snow.
• B. rain.
• C. water vapor.
• D. groundwater.

17
Quick Check

• The suns energy reaches Earth through
• A. evaporation.
• B. condensation.
• C. radiation.
• D. wind.

18
Quick Check

• What process produces rain?
• A. condensation
• B. evaporation
• C. warming
• D. solidification

19
Quick Check

• Water vapor is a
• A. liquid
• B. solid
• C. gas
• D. form of energy

20
Quick Check

• The cooling of water vapor leads FIRST to
• A. cloud formation.
• B. evaporation.
• C. formation of groundwater.
• D. precipitation.

21
Quick Check

• What process produces a cloud?
• Evaporation
• Condensation
• Radiation
• warming

22
Lesson 11The Worlds Oceans

• EQ How does the composition and topography of
  earths oceans vary by location?

23
Location of the Worlds Oceans

• The Pacific Ocean is the largest ocean. It is
  bordered by North America, South America, Asia,
  Australia, and Antarctica
• The Atlantic is the second largest ocean. It is
  bordered by N. America, S. America, Africa,
  Europe, and Antarctica.
• The third largest ocean is the Indian Ocean. It
  lies between the countries of India, Pakistan,
  Australia, and the continents of Africa and
  Antarctica.

24
Composition of the Worlds Oceans

• The main substance dissolved in ocean water is
  sodium chloride (NaCl) or table salt.
• Other dissolved solid substances are sulfate,
  magnesium, calcium, and potassium.
• Solid substances dissolved in sea water come from
  rivers, streams, rocks from the shore, volcanoes
  and underwater hot springs.
• The concentration of all the dissolved substances
  in sea water is about 3.5.

25
Composition of the Worlds Oceans

• The oceans also hold dissolved gases, such as
  oxygen and carbon dioxide.
• Marine life such as fish need dissolved oxygen in
  sea water to live.
• Sea plants such as seaweeds need carbon dioxide
  to survive. They get it from the dissolved
  carbon dioxide in sea water.

26
Topography of the Worlds Oceans

• Oceanographers have mapped the ocean floors by
  using special equipment.
• Echo sounding, (pings), measure the time it takes
  a pulse of sound to go from the ship to the ocean
  floor and echo back to the ship.
• The speed of sound in sea water averages about
  1520 m per second.

27
Quick Check

• Which continents border the Atlantic Ocean?
• A. North America, South America, Asia, Australia
• B. Asia, Australia, Africa
• C. North America, South America, Europe, Africa
• D. South America, Europe, Asia, Australia

28
Quick Check

• Which substance do fish need to live and take in
  from water that you take in from air?
• A. salt
• B. oxygen
• C. carbon dioxide
• D. water

29
Quick Check

• Pings from an echo sounder aboard a ship make a
  round trip in 8 seconds. How far beneath the
  ship is the ocean floor?
• A. 2,920 meters
• B. 6,080 meters
• C. 11,680 meters
• D. 23,360 meters

30
Quick Check

• Which shows the order of Earths three major
  oceans from largest to smallest?
• A. Pacific, Atlantic, Indian
• B. Atlantic, Pacific, Indian
• C. Indian, Atlantic, Pacific
• D. Atlantic, Indian, Pacific

31
Quick Check

• If you were to walk along the ocean bottom from a
  beach, which of the following features would you
  reach after the continental shelf?
• A. the abyssal plain
• B. a seamount
• C. the mid-ocean ridge
• D. the continental slope

32
Quick Check

• About how deep is the deepest pat of the worlds
  oceans?
• A. 4000 meters
• B. 8000 meters
• C. 11,000 meters
• D. 14,000 meters

33
The Water CycleSection 11-1

• How is Earths water distributed among saltwater
  and freshwater resources?
• How does Earths water move through the water
  cycle?
• How do people and other living things use water?

34
Water on Earth

• Most of Earths water is saltwater (97)
• Most saltwater is found in the oceans
• Only about 3 of water is freshwater
• All living things must share about 1 of the
  total amount of water on Earth

35
(No Transcript)
36
Distribution of Water on Earth

• Saltwater oceans and lakes (97)
• Freshwater (3)
• Ice (76)
• Shallow Groundwater (12)
• Deep Groundwater (11)
• Lakes and rivers (.34)
• Water Vapor (0.037)
• All living things share less than 1 of total
  water on Earth!

37
The Water Cycle 1

• Water is naturally recycled through a process
  known as the water cycle
• Water moves from bodies of water, land, and
  living things from Earths surface, up to the
  atmosphere and then back to Earths surface.
• Steps for the water cycle are evaporation,
  condensation, and precipitation

38
The Water Cycle 2

• The source of energy that drives the water cycle
  is the SUN!
• Clouds formation water vapor loses energy,
  cools down, condenses into liquid water droplets,
  droplets clump together around tiny dust
  particles, forming clouds
• Most evaporated water comes from oceans, and most
  precipitation falls back into the oceans

39
The Water Cycle 3

• Evaporation the process by which liquid water
  on the surface change to a gas
• Condensation process by which gas molecules
  change into a liquid. This process forms clouds
• Precipitation process in which clouds become
  too heavy to hold the water droplets, and the
  droplets fall to the Earths surface as rain,
  sleet, snow or hail

40
How Do People Use Water?

• Humans use water for household purposes,
  agriculture, industry, transportation, and
  recreation.
• Irrigation is the process of supplying water to
  areas for growing crops
• Industry to make products, cool off machines
• Transportation travel upon the oceans, lakes
  and rivers
• Recreation exercise and sports

41
Water and Living Things

• Water important for living things to grow,
  reproduce and carry on other essential processes.
• Photosynthesis process of water, carbon dioxide
  and sunlight to make their own food
• Habitat place an organism lives and provides
  the things it needs to survive

42
Quick Check

• More than 97 of Earths total water supply is
  found in
• A. ice sheets.
• B. groundwater.
• C. the atmosphere.
• D. the oceans.

43
Quick Check

• The energy the drives the water cycle comes from
• A. the sun.
• B. the Earth.
• C. the rain.
• D. oceans.

44
Quick Check

• Rain that falls on a steep, paved street during a
  thunderstorm will most likely become
• A. groundwater.
• B. runoff.
• C. a spring.
• D. a reservoir.

45
Quick Check

• More than two-thirds of Earths freshwater is
  found in
• A. rivers and streams.
• B. ponds and lakes.
• C. glaciers and icebergs.
• D. wetlands.

46
Quick Check

• How does the water cycle renew Earths supply of
  fresh water?
• A. evaporation.
• B. condensation
• C. the sun
• D. precipitation

47
Ocean Water Chemistry

• How salty is ocean water?
• How do the conditions in the ocean change with
  depth?
• Describe one factor that increases the salinity
  of seawater and one factor that decreases
  salinity.

48
The Salty Ocean

• The average amount of salt in ocean water is
  about 3.5 or 35 grams of salt per one kilogram
  of water
• Ocean water carries many different dissolved
  salts
• Sodium Chloride (table salt) is the most abundant
  salt in the ocean
• Factors increasing salinity include evaporation
  and freezing factors decreasing salinity include
  precipitation and rivers
• Most oxygen in oceans come from the atmosphere
  because it is closer to the surface of the water.

49
The Salty Ocean

• Two gases found in the oceans are necessary for
  living things oxygen and carbon dioxide
• Temperature decreases in the ocean with depth
• Pressure increases with depth in the ocean
• Scuba divers are prevented from descending father
  than 40 m because of pressure

50
Divisions of the Global Oceans

• Pacific- the largest ocean getting smaller
• Atlantic- the second largest getting larger
• Indian- third largest
• Southern- located along the border of Antarctica
• Artic- smallest ocean most oceanographers
  consider it as an extension of the Pacific,
  Atlantic, and Indian Oceans

51
How Did the Oceans Form?

• About 4 billion years ago, the Earth cooled
  enough for water vapor to condense.
• The water began to fall as rain.
• The rain filled the deeper levels of Earths
  surface and the first oceans began to form.

52
Characteristics of Ocean Water

• Ocean water is salty
• Chock-full of solids
• Climate affects salinity
• Water movement affects salinity
• Temperate zones
• Surface temperature Changes

53
Ocean Water is Salty

• Most of the salt found in oceans is sodium
  chloride (table salt).
• Salts have been added to the oceans for billions
  of years by running waters (rivers, streams)
  which dissolve various minerals, and then dump
  the water into the oceans.
• Also, solid materials come from volcanic
  eruptions, hot springs, ocean waves crashing
  against rocks

54
Chock-Full of Solids

• Salinity- the measure of the amount of dissolved
  salts in a given amount of water.
• Measured in grams (g).
• 1 kg (1000 g) of ocean water carries an average
  of 35 g of salt (3.5).
• During the water cycle, fresh water from the
  ocean is evaporated leaving only the salts behind.

55
Climate Affects Salinity

• Some parts of the ocean are saltier than other
  parts of the ocean.
• Coastal waters in places with hotter, drier
  climates have a higher salinity.
• Coastal waters in places with cooler, more humid
  climates have a lower salinity.
• Main reason evaporation
• Coastal waters have less salinity because more
  fresh water from rivers run into the oceans in
  these areas.

56
Water Movement Affects Salinity

• Some parts of the ocean (bays, seas, gulfs) move
  less than other parts.
• Also, some parts of the open ocean that do not
  have currents run through them can be slow
  moving.
• Slower-moving areas of water develop high
  salinity.

57
Temperate Zones

• Temperature of ocean water decreases with depth.
• Water in the ocean is divided into three layers
  by temperate.
• Top layer (surface zone)
• Middle layer (thermocline zone)
• Bottom layer (deep zone)

58
Temperature Changes

• Temperature in the surface zones vary with
  latitude and the time of the year.
• Parts of the ocean along the equator are warm
  because it receives more direct sunlight per year
  than areas closer to the poles.

59
Quick Check

• Ocean water is more dense than freshwater at the
  same temperature because of
• A. pressure.
• B. salinity.
• C. the Coriolis effect.
• D. upwelling.

60
Quick Check

• The most common substances dissolved in ocean
  water are
• A. sodium and chloride.
• B. potassium and chloride.
• C. potassium and sodium.
• D. calcium and chloride.

61
Quick Check

• The concentration of all dissolved substances in
  seawater is 3.5. How many grams of dissolved
  substances are in 200 grams of saltwater?
• A. 3.5
• B. 7.0
• C. 57
• D. 200

62
Quick Check

• What is the salinity of saltwater?
• As you descend deeper into the ocean temperature
  _____________ and pressure __________.
• The two sources of oxygen in ocean water are
  __________ and __________.

63
Exploring the Ocean

• EQ What are some features of the ocean floor?

64
What factors make ocean floor research
difficult?

• Because of darkness, cold, and extreme pressure,
  scientists had to develop new technology to
  enable them to study the deep ocean floor.
• SONAR stands for sound navigation and ranging.
• Oceanographers study the oceans by
• -sonar
• -satellite

65
What are some of the features of the ocean floor?

• The eight features of the ocean floor are
• Continental shelf a gentle sloping, shallow area
  of the ocean floor that extends outward from the
  edge of the continent.
• Continental slope marks the true edge of a
  continent, a steady slope where rock that makes
  up the continent stops and the rock that makes up
  the ocean floor begin.
• Seamounts mountains completely under water
  extinct volcanoes

66
What are some of the features of the ocean floor?

• Abyssal plain smooth, flat region of the ocean
  floor
• Mid-ocean ridge a continuous range of mountains
  that wind around Earths ocean floor.
• Volcanic Island very tall mountains created by
  the cooling and hardening of erupting volcanoes
  on the ocean floor.
• Deep-sea Trench canyons on the ocean floor that
  are the deepest spots on Earth.
• Guyot- flat-top mountain flattened by the action
  of waves
• SONAR stands for sound navigation and ranging.
  It is a system that uses sound waves to calculate
  the distance to an object.

67
Quick Check

• A smooth, nearly flat region of the ocean floor
  is call a(n)
• A. trench.
• B. mid-ocean ridge.
• C. abyssal plain.
• D. sea mount.

68
Quick Check

• Which ocean floor feature makes up the deepest
  parts of the ocean?
• A. abyssal plain
• B. mid-ocean ridge.
• C. deep-sea trench.
• D. sea mount

69
Quick Check

• What three (3) factors make ocean floor research
  difficult?
• _______
• ______
• ______

70
Quick Check

• What are some features of the ocean floor?
• __________
• __________
• __________
• __________
• __________
• __________

71
Lesson 12Waves, Currents, and Tides

• EQ What causes the ocean to move?

72
Waves

• A wave is a disturbance that transfers energy
  through matter or space.
• Wind transfers energy into the sea causing waves
  to occur.
• Undersea earthquakes and landslides can also put
  energy into the water to produce ocean waves.

73
Waves

• The size of a wave depends on the amount of
  energy that is transferred to the water.
• The amount of energy transferred depends on three
  things
• Wind speed
• Length of time it blows
• Distance over which it blows
• As each of these factors increase, so does the
  size of the wave.

74
Ocean Currents

• Winds are responsible for ocean currents.
• A surface current is an ocean current that moves
  along the top part of an ocean.
• Surface currents are moved by prevailing winds.
• Prevailing winds are winds that blow in regular
  directions almost all the time.

75
Ocean Currents

• Surface currents can be cold or warm.
• Those that flow from the poles toward the equator
  are cold.
• Those that flow from the equator towards the
  poles is warm.
• The Gulf Stream is a warm current that flows
  northward up the east coast of the United States
  toward Great Britain and western Europe.

76
Tides

• A tide is the rise and fall of the oceans
  surface caused mostly by the gravitational pull
  of the moon.
• At high tide, the ocean water has risen as high
  as it will go on a shore.
• At low tide, the ocean water has fallen as low as
  it can go on a shore.

77
Tides

• Earths rotation on its axis affects which tides
  will occur at a certain place on Earth.
• High tides occur about every 12 hrs.
• Low tides occur about every 12 hours.
• The time between low tide and high tide is about
  6 hrs.

78
Quick Check

• What causes tides but NOY waves and currents?
• A. winds and the moons gravity
• B. mostly the moons gravity
• C. mostly the suns gravity
• D. only winds

79
Quick Check

• What is the main cause of the Gulf Stream?
• A. storms
• B. winds that blow now and then
• C. winds that blow in regular directions
• D. the moons gravity

80
Quick Check

• If the first high tide of the day occurs at 100
  a.m., the next high tide will come closest to
• A. 700 a.m.
• B. 700 p.m.
• C. 100 a.m. the next day
• D. 100 p.m.

81
Quick Check

• What is the cause waves and currents but NOT
  tides?
• A. wind
• B. the moons gravity
• C. the suns gravity
• D. Earths gravity

82
Quick Check

• What is the cause of most ocean waves?
• The climate
• The large ships in the ocean
• The moon
• The wind

83
Quick Check

• A wave will increase in height when the distance
  over which the wind blows over the sea
• A. increases.
• B. decreases.
• C. stays the same.
• D is 0 kilometers.

84
Quick Check

• The wave will increase in height when the speed
  of the wind
• A. remains unchanged for a long time.
• B. decreases.
• C. increases.
• D. changes direction.

85
Quick Check

• Which will produce the highest wave?
• A. wind speed of 10 km/h
• B. wind speed of 20 km/h
• C. wind speed of 30 km/h
• D. wind speed of 40 km/h

86
Quick Check

• Which unit of measurement would you use to
  express the area of the Atlantic Ocean?
• A. m
• B. km
• C. m²
• D. km²

87

• Section 13 1Wave Action

88
Wave Action

• How does a wave form?
• How does wavelength and wave height change as a
  wave enters shallow water?
• How do water particles move within a wave?

89
How Waves Form

• Most waves form when winds blowing across the
  waters surface transmit their energy to the
  water.
• Near shore, the wave height increases and the
  wavelength decreases.
• As the energy in a wave passes, water particles
  move in a circular path, ending in their original
  position.

90
Describing Waves

• Crest highest part of a wave
• Trough lowest part of a wave
• Wavelength horizontal distance between crests
  or troughs
• Wave height vertical distance from the crest to
  the trough
• Frequency number of waves that pass a point in
  a certain amount of time

91
How Waves Change Near Shore

• In deep waters, waves travel as long, low waves
  called swells.
• Near shore, the wave height increases and the
  wavelength decreases.
• When the wave reaches a certain height, the crest
  of the wave topples. The wave breaks onto the
  shore, forming surf.

92
How Waves Affect the Shore

• Longshore Drift movement of sand along the
  beach
• Rip Currents a rush of water that flows rapidly
  back to sea through a narrow opening
• Sandbar as waves slow down, they deposit the
  sand they are carrying on the shallow, underwater
  slope in a long ridge

93
Reducing Beach Erosion

• Over time, erosion can wear away a beach
• Threatens homes, buildings, property
• groin a wall of rocks or concrete to reduce
  erosion along a stretch of beach
• Building groins can increases the amount of
  erosion father down the beach

94
Quick Check

• What is the cause of most ocean waves?
• The climate
• The large ships in the ocean
• The moon
• The wind

95
Quick Check

• Rolling waves with a large distance between
  crests have a long
• wave height
• wavelength
• frequency
• trough

96
Quick Check

• Groins are built to reduce the effect of
• tsunamis.
• longshore drift.
• rip currents.
• deep currents.

97
Quick Check

• Sand is gradually carried down the beach by
• groins
• sandbars
• crests
• longshore drift

98
Section 13 - 4

• Currents and Climate
• EQ What forces cause surface currents and deep
  currents?

99
Surface Currents

• Surface currents are driven mainly by winds and
  follow global wind patterns, moving in circular
  patterns in ocean basins.
• Surface currents affect water to a depth of
  several hundred meters.
• Coriolis effect- the effect of Earths rotation
  on the direction of winds and currents

100
How Surface Currents Affect Climate

• A surface current warms or cools the air above
  it, influencing the climate of the land near the
  coast.
• Climate is the pattern of temperature and
  precipitation typical of an area over a long
  period of time.
• Currents affect climate by moving cold and warm
  water around the globe.
• Currents are large streams of moving water that
  flow through the oceans

101
Deep Currents

• Deep currents are caused by differences in
  density rather than surface winds.
• Cold waters at the bottom of the ocean creep
  slowly across the ocean floor.
• Deep currents move and mix water around the
  world.
• They move much slower than surface currents.

102
Upwelling

• Upwelling is the upward movement of cold water
  from the ocean depths.
• As wind blows away the warm surface water, cold
  water rises to replace it.
• Upwelling brings up tiny ocean organisms,
  minerals, and other nutrients from the deeper
  layers of the water.

103
El Niño

• El Niño- an abnormal climate event that occurs
  every 2 to 7 years in the Pacific Ocean.
• This causes a sheet of warm water to move
  eastward toward the South American coast.
• El Niño can last for one to two years before the
  usual winds and currents return.

104
Quick Check

• Winds and currents move in curved paths because
  of
• the Coriolis effect.
• longshore drift.
• wave height.
• tides.

105
Quick Check

• Currents are caused by
• gravitational pull of the moon.
• gravitational pull of the sun.
• Winds, the earths rotation, and differences in
  water density.
• the earths rotation.

106
Quick Check

• What causes tides but NOT waves and currents?
• A. winds and the moons gravity
• B. mostly the moons gravity
• C. mostly the suns gravity
• D. only winds

107
Quick Check

• What is the MAIN cause of the Gulf Stream?
• A. storms
• B. winds that blow now and then
• C. winds that blow in regular directions
• D. the moons gravity

108
Section 13 - 2

• Tides
• EQ What causes tides?

109
Tides

• What causes tides?
• How can tides be used to generate electricity?
• Describe the positions of the sun and the moon,
  in relation to Earth when spring tides occur.

110
What causes tides?

• Tides are caused by the interaction of Earth, the
  moon, and the sun.
• The moon pulls on the water on the side closest
  to it more strongly than it pulls on the center
  of the Earth.
• This pull creates a bulge of water, called a
  tidal bulge, on the side of Earth facing the
  moon.
• The water opposite the moon is pulled toward the
  moon less strongly than the water facing the
  moon.
• This water is left behind, forming a second
  bulge.

111
The Daily Tide Cycle

• As Earth turns completely around once each day,
  people on or near the shore observe the rise and
  fall of the tides as they reach the area of each
  tidal bulge.
• The high tides occur about 12 hrs. and 25 mins.
  Apart in each location.

112
The Monthly Tide Cycle

• Changes in the positions of Earth, the moon, and
  the sun affect the height of the tides during a
  month.
• Twice a month, at he new moon and the full moon,
  the sun and moon are in a straight line.
• 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 month, the sun and moon pull at
  right angles to each other, producing a neap
  tide.
• A neap tide is a tide with the least difference
  between low and high tide.
• The movement of large amounts of water between
  high and low tide are a source of potential
  energyenergy that is stored and waiting to be
  used.

113
Quick Check

• At the full moon, the combined gravitational
  pulls of the sun and the moon produce a
• A. surface current.
• B. neap tide.
• C. spring tide.
• D. rip current.

114
Quick Check

• A tide which water reaches its lowest point on
  the beach each day is called
• A. neap tide.
• B. high tide.
• C. spring tide.
• D. low tide.

115
Quick Check

• Tide with the least difference between high and
  low tide is called
• A. neap tide.
• B. high tide.
• C. spring tide.
• D. low tide.

116
Quick Check

• A tide in which water reaches its highest point
  on the beach each day is called a
• A. neap tide.
• B. high tide.
• C. spring tide.
• D. low tide.

117
Quick Check

• If the first high tide of the day occurs at 100
  am, the next high tide will come closest to
• A. 700 am
• B. 100 am the next day
• C. 700 pm
• D. 100 pm

118
Quick Check

• Tide with the greatest difference between high
  and low tide is called a
• A. neap tide.
• B. high tide.
• C. spring tide.
• D. low tide.

119
Quick Check

• High tides occur
• A. once every two days.
• B. once a day.
• C. twice a day.
• D. four times a day.