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4.4Unit 3: The Solar System and energy

Tides — Cambridge Checkpoint Earth & Space 0893 Revision Notes & Topical Questions

5 min read 10 parts Lesson 4 of 7 1 quiz

📚 Cambridge Checkpoint Earth & Space 0893 Hub / Topical Revision
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Lesson summary

4.4 Tides — CHECKPOINT EARTH AND SPACE 0893 notes: Describe tides, explain their cause by the gravity of the Moon and Sun and describe their effects.Tide = the regular change in depth of the ocean in a place during the dayDepth — the distance from the water surface to the ocean b…

  • Tidal range
  • Largest range
  • Smallest ranges
  • Earth tide
  • High tides
  • High to low

Section 1 of 10What tides are

Tide
Tide the regular change in depth of the ocean in a place during the day
Depth
  • Depth the distance from the water surface to the ocean bottom
Tidal range
Tidal range the difference in depth of water between high and low tides
Largest range
  • 16.3 m in the Bay of Fundy, Canada
Smallest ranges
  • Smallest ranges the Caribbean and Mediterranean seas have very small tidal ranges
Earth tide
  • Earth tide the land also rises and falls by about 30 cm each day

Section 2 of 10Timing of tides

High tides
  • High tides they are about 12 hours apart
Low tides
  • Low tides they are also about 12 hours apart
High to low
  • High to low the time from a high tide to the next low tide is six hours
Two a day
  • Two a day a place has two high tides and two low tides every day

Section 3 of 10Tidal force from the Moon

Moon's gravity
  • Moon's gravity the Moon is held in orbit by the Earth's gravity but its own gravity pulls on the Earth
Tidal force
Tidal force the pull of the Moon's gravity that causes tides
Water and land
  • Water and land the pull moves the water of the oceans more easily than the land
Near side
  • Near side the side of the Earth closer to the Moon has a high tide
Far side
  • Far side the side furthest from the Moon also has a high tide

Section 4 of 10Why high tides are 12 hours apart

1
The Earth spins once on its axis in 24 hours.
2
A place facing the Moon has a high tide.
3
After 12 hours the same place is on the opposite side of the Earth.
4
The bulge of water on the far side gives it a second high tide.
5
So a place has high tides 12 hours apart.

Section 5 of 10The Sun and the tidal range

Sun's tidal force
  • Sun's tidal force the Sun also produces a tidal force but weaker because it is further away than the Moon
Alignment
  • Alignment when the Sun, Moon and Earth are in line the tidal forces add together
Greatest range
  • Greatest range this happens at full Moon and new Moon
Frequency
  • Frequency it happens twice each lunar month

Section 6 of 10Effects of tides

Harbours
  • Harbours some can be used only at certain times because boats need enough depth
Flooding
  • Flooding coastal areas are more likely to flood at high tide in strong winds
Small boats
  • Small boats the flow of water in and out of some coasts can be dangerous
Food chains
  • Food chains at low tide birds eat shellfish that are uncovered, and some fish move with the tides
Earth tides
  • Earth tides they have been linked with volcano eruptions and earthquakes
Energy
  • Energy moving tidal water can be used to generate electricity

Section 7 of 10How the cause of tides was found

Observation
  • Observation in 330 BCE a Greek sailor noticed the depth changed twice a day and linked it to the Moon
Early idea
  • Early idea around 1600 a German scientist suggested a magnetic attraction between the Moon and water, which is now known to be wrong
Solution
  • Newton calculated tidal forces from gravity in 1687
Acceptance
  • Acceptance his calculations were accurate enough to show gravity from the Moon and Sun causes tides

Section 8 of 10More from the specification

1Planetary orbits and gravitational scale
  • Planetary orbits and gravitational scale celestial bodies travel along elliptical orbits, with tidal force scale varying among gravitational groups.
2Differential lunar gravity
  • The gravitational pull of the Moon is stronger on the side of Earth facing it and weaker on the far side, stretching oceanic water into two tidal bulges.
3Diurnal tidal cycle
  • As the Earth rotates through the two ocean bulges once every 24 hours and 50 minutes, most coastlines experience two high and two low tides.
4Tidal amplitude factors
  • Coastal geography, ocean floor topography, and astronomical alignments combine to dictate local tidal heights.
5Sun's tidal contribution
  • Although much further away than the Moon, the Sun's immense mass produces significant solar tides that amplify or dampen lunar tides.
6Group
  • A column of the Periodic Table.
Tidal force
  • Tidal force the Moon pulls harder on the near side of the Earth than on the far side, and this difference produces the two bulges of water.
Spring tides
  • Spring tides the Sun, Moon and Earth in line give the largest tidal range.
Neap tides
  • Neap tides when the Sun and Moon pull at right angles the forces partly cancel and the tidal range is smallest.
Two a day
  • Two a day as the Earth turns, a place passes through both bulges, so it has two high tides and two low tides each day.

Section 9 of 10Key terms

TermMeaning
TideRegular rise and fall of the ocean depth.
Tidal rangeDifference in water depth between high and low tides.
Tidal forcePull of gravity from the Moon and Sun that causes tides.
Earth tideDaily rise and fall of the land.
HarbourPlace where boats load and unload.
CoastalClose to the ocean.

Section 10 of 10Exam technique

1
Thinking tides are caused by wind — they are caused by the gravity of the Moon and Sun.
2
Thinking only the side facing the Moon has a high tide — the far side also has one.
3
Thinking the Sun has the greatest tidal force — it is weaker than the Moon because it is further away.
4
Thinking high tides are 6 hours apart — high tides are about 12 hours apart.

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