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GEOL200 > Week 8: Tides and coastlines > Flashcards

Week 8: Tides and coastlines Flashcards

1
Q

What is a tide?

A

Periodic short-term changes in height of ocean surface caused by the combination of the gravitational force of the Moon and the Sun and motion of the earth

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2
Q

Are tides a wave?

A

Yes, a huge one
- wavelength 1/2 of the earth’s circumference

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3
Q

What do tides need to keep moving?

A

Needs to remain under the influence of the force that created it gravity

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4
Q

What causes tides?

A

Gravitational pull of moon and sun acting on the ocean and the earth’s rotation

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5
Q

Sun vs moon

A

The sun has half the role of the moon on tides

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6
Q

What is the barycentre?

A

The centre of mass of two orbiting bodies
** earth-moon system revolves once a month (27.3 days) around centre of mass

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7
Q

Newton’s law of universal gravitation

A

Every object that has a mass in the universe is attracted to every other object
- if mass increases, gravitational force increases
- if distance increases, gravitational force decreases

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8
Q

Centripetal forces

A

Required to keep identical sized particles in identical-sized orbits as the result of the rotation of the earth-moon system around barycentre
**all arrows equal and same direction

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9
Q

Resultant forces

A

What generates tides
Two vectors (gravity and centripetal force)- diff btwn them creates 2 bulges of water

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10
Q

Tidal bulges

A

Earth rotates under the water bulges

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11
Q

How long does it take for a full tidal cycle?

A

24 hours and 50 min

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12
Q

Lunar bulges

A

Moon revolves around earth is same direction as earths rotation
Takes an extra 50 min for earth to catch up to moon

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13
Q

Lunar day

A

Time of day when the moon is highest in the sky and the next time of day when is is at its highest again

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14
Q

Role of the sun

A

Creates 2 solar bulges

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15
Q

Spring tide

A

Tide of max range
Occurs every 2 weeks when moon is in new or full moon phase
**greatest gravitational attraction bc moon, sun and earth are all in alignment
**coastal flooding and storm surge

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16
Q

Neap tide

A

Tide of minimal range
Occurs every 2 weeks when moon is in 1st quarter or 3rd quarter phase (7 day after spring tides)
**low gravitational attraction bc moon and sun are at right angles

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17
Q

What are the three tidal patterns?

A
  1. Diurnal
  2. Semidiurnal
  3. Mixed semidiurnal
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18
Q

Diurnal

A

1 high tide, 1 low tide
ex. gulf of mexico

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19
Q

Semidiurnal

A

2 high, 2 low (equal heights)
ex. atlantic coast

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20
Q

Mixed semidiurnal

A

2 high, 2 low (unequal heights)
ex. pacific coast

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21
Q

Tidal range

A

Vertical diff btwn consecutive high and low tides

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22
Q

Macrotidal

A

> 4 m

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23
Q

Mesotidal

A

2 to 4 m

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24
Q

Microtidal

A

<2 m

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25
Q

Greatest tidal range in the world and why?

A

Bay of Fundy (15-17m)
Basin shape is restricted

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26
Q

Two ways to explain tides

A
  1. Equilibrium theory of tides
  2. Dynamic theory of tides- Amphidromic circulation
27
Q

Equilibrium theory of tides

A

Ignore ocean basins and coastlines, ocean that covers entire earth

28
Q

Dynamic theory of tides

A

More complex situation- continents, coastlines, coriolis effect, water depth etc.

29
Q

Amphidromic circulation

A

Water sloshes from left to right at side of basin
Tide as rotary wave- moves around a central part
**tide is a counterclockwise rotation in northern hemipshere

30
Q

Amphidromic point

A

Locations where there are little or no tide in the ocean

31
Q

Tidal flats- Mudflats

A

Coastal wetlands form in intertidal zone; submerges and emerges 2x day

32
Q

Tidal currents

A

Caused by rise and fall in water as a tide crest approaches and passes

33
Q

Flood current

A

Water moving towards land, rising water levels

34
Q

Ebb current

A

Water moving away from land, falling water levels

35
Q

Slack water

A

No movement either towards land or offshore

36
Q

Tidal zones

A
  1. Subtidal
  2. Intertidal
  3. Supratidal
37
Q

Subtidal zone

A

Always underwater, below tide line

38
Q

Intertidal zone

A

Tidal flat, exposed then submerged then exposed
High biodiversity, cant live here

39
Q

Supratidal zone

A

Almost never covered by water, except for when high tide w storm surge

40
Q

Tidal bore

A

Flood tide creates a wave of water that travels upriver
Large tidal ranges
Incoming tide moves into narrow opening

41
Q

Zones of a coastline

A
  1. Coast
  2. Shore
42
Q

Coast

A

Extends inland as far as coastal processes reach

43
Q

Shore

A

Low tide and highest point storm waves reach

44
Q

Parts of the shore

A
  1. Backshore
  2. Foreshore
  3. Offshore/nearshore
  4. Shoreline
45
Q

Shoreline

A

Position changes; at water’s edge

46
Q

Backshore

A

Above high tide level

47
Q

Foreshore

A

Exposed at low tide, covered at high tide

48
Q

Nearshore

A

From low tide shoreline to breaking waves

49
Q

Beach

A

Wave-worked sediment

50
Q

Beach face

A

Wet sloping surface

51
Q

Berm

A

Shore-parallel ridge, dry sediment, high tide mark, mobile

52
Q

Shephard coastal classification

A
  1. Primary coasts
  2. Secondary coasts
53
Q

Variables that effect the classification of coastlines?

A

Materials, processes, forms, developmental age, environment, human impact

54
Q

Primary coasts

A

Formed by non-marine processes (such as volcanic activity) ; young, possible strong terrestial influence

55
Q

Secondary coasts

A

Shaped by marine processes; erosional or depositional processes dominate

56
Q

Shephard Coastal classification- primary

A
  1. Land erosional coast
  2. Subaerial depositional coast
  3. Volcanic coasts
  4. Fault/tectonic coasts
  5. Glacial/ice coasts
57
Q

Land erosional coast

A

Subaerial coast
Post glacial sea level rise
Drowned coast

58
Q

Subaerial depositional coast

A

Deposition by rivers, glaciers, wind, landslides

59
Q

Shephard coastal classification- secondary

A
  1. Wave erosion coasts
  2. Marine deposition coasts (beaches and barriers)
  3. Coasts built by organisms (reefs)
60
Q

Submergent coasts

A

Drowned coastal zones
Coastal land is sinking relative to sea level (transgressive)
Land subsidence or sea level rise

61
Q

Emergent coasts

A

Wave-cut terraces and platforms are exposed
Coastal land is rising relative to sea level (regressive)

62
Q

Erosional coast

A

Dominant processes are those that remove coastal material
EROSION>DEPOSITION
**more material being removed than added

63
Q

Depositional coast

A

Material accumulated
EROSION<DEPOSTION
**More material added than removed

GEOL200 (10 decks)

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