CAMBRIDGE INTERNATIONAL AS & A LEVEL MARINE SCIENCE: COURSEBOOK ANSWERS
Exam-style questions and sample answers have been written by the authors. In examinations, the
way marks are awarded may be different.
Coursebook answers
occurring, so the highest tide is lower than
normal. A lower tide means less of a storm
surge, so there will be less flooding and erosion
of the shore.
Chapter 2
Test yourself questions
1
2
Tsunamis form when submarine earthquakes
or volcanoes erupt, releasing large amounts of
stored energy that move the large volume of
water above them. This movement creates
a long-wavelength wave that builds until it
reaches shallow water. At that point, the wave
increases in size and crashes onto the shore,
causing great damage.
3
New rock is created at divergent boundaries
as magma emerges from the crust, cools
and solidifies. Old rock is destroyed at
convergent boundaries as oceanic crust sinks
into the asthenosphere and slides under
continental crust.
4
5
6
7
8
1
Continental drift theory (CDT) is an earlier
version of plate tectonics (PT). In both
theories, fossil evidence, fit of the coastlines
and geological structures on multiple
continents are used to show that the planet’s
continents are moving apart. CDT failed to
provide the mechanism for the movement,
thus making it an incomplete theory.
Extreme. Hydrothermal vent systems are
under immense pressure, lack light and
have a wide range of water temperatures.
Additionally, the water is made toxic due to
the sulfuric acid and heavy metals present in
the water.
Answers will vary. Many students confuse
these concepts or think they are two words
that mean the same thing.
Deltas, estuaries and muddy shores require a
large amount of sedimentation and deposition.
Erosion removes weathered materials from the
large rocks that make up a rocky shore. It also
carries away sediments that would cover the
rocks, keeping them clear for animal attachment.
Answers should indicate that a quarter moon
would be preferable because a neap tide is
9
Currents at the surface are masses of water
blowing in the same direction caused by the
wind. Deep-water currents are moved by
density changes. Tides are the predictable
movement of water based on the gravitational
effects of the Moon and Sun. Tides are not
affected by winds, density or temperature.
10 El Niño reduces productivity when upwelling
stops as nutrient-rich bottom water is unable
to reach the surface. This damages the food
web as producers are unable to grow and
reproduce. During La Niña the reverse is
true. Greater than normal amounts of cold,
nutrient-rich water is allowed to upwell. This
allows for higher-than-average productivity
and a stronger food web.
11 Answers will vary.
Maths skills 2.1 questions
1
Date
High tide
level / m
Low tide
level / m
Tidal
range / m
1 June
0.55
0.50
0.05
2 June
0.59
0.46
0.13
3 June
0.66
0.31
0.35
4 June
0.76
0.13
0.63
5 June
0.90
−0.06
0.96
6 June
0.98
−0.23
1.21
7 June
1.05
−0.37
1.42
8 June
1.13
−0.46
1.59
9 June
1.18
−0.50
1.68
10 June
1.19
−0.48
1.67
Cambridge International AS & A Level Marine Science © Cambridge University Press 2020
CAMBRIDGE INTERNATIONAL AS & A LEVEL MARINE SCIENCE: COURSEBOOK ANSWERS
Date
11 June
1.15
−0.42
1.57
Core practical activity 2.1
12 June
1.05
−0.31
1.36
Before you start
13 June
0.90
−0.17
1.07
14 June
0.72
−0.02
0.74
15 June
0.53
0.12
0.41
16 June
0.34
0.25
0.09
2
a
Low tide
level / m
specific changes in its pattern that are directly
caused by climate change.
High tide
level / m
Tidal
range / m
1
Answers will vary, but should be logically
justified based on prior information.
2
Answers will vary, but anywhere between
1 and 10 minutes is standard.
3
Time is the dependent variable because that is
what is being measured, and it is the variable
that will change due to scientist-controlled
variations (for example, sediment size).
Sample answer
Tidal range / m
1.8
1.6
Evaluation and conclusions
1.4
1
Answers will vary. Students may say seconds if
they were basing their choice on how quickly the
pebbles would settle, or they may choose minutes
in expectation that the silt would take a while.
2
Students should describe the overall trend that
as sediment diameter increases, settling time
decreases.
3
The tube demonstrates the settling rates on the
different types of shore found in the littoral
zone. The pebbles represent rocky shores; the
sand represents sandy shores; and the fine
sand / silt represents a muddy shore.
4
Rocky shore, sandy shore, muddy shore.
5
The pebbles, like larger rocks, settle quickly
and can withstand a greater amount of
wave action without being eroded. The silt
takes a very long time to settle, and the
slightest movement of water stirs it up again.
Therefore, a muddy shore needs to have little
or no wave action in order to have a substrate.
1.2
1.0
0.8
0.6
0.4
0.2
1 June
2 June
3 June
4 June
5 June
6 June
7 June
8 June
9 June
10 June
11 June
12 June
13 June
14 June
15 June
16 June
0.0
Date
b9 June should be circled because tidal
range is the highest during spring tides.
c
1 June and 16 June should have a square
around them because tidal range is the
lowest during neap tides.
Case study 2.1 questions
1
2
The top image represents La Niña. This is
evidenced by the hurricanes in the Atlantic, as
well as strong trade winds in the Pacific pushing
rain clouds toward Indonesia. The bottom
image is El Niño, as evidenced by the weak trade
winds and very warm water across the Pacific.
2
Sea surface temperatures will rise during El
Niño events, regardless. There could be other
reasons for the rise in the Pacific, or it could
just be occurring naturally in response to
normal ENSO cycling, which is irregular.
3
Correlation does not equal causation. Global
weather patterns are very complicated and
can be adjusted by many factors. Since ENSO
activity has been irregular throughout its
historical record, it is difficult to pinpoint
Reflection
1
Answers will vary; students should mention
human error, timing inconsistencies, and the
use of means to control for errors.
2
Scientists can use models to make predictions
about real-world situations. Models like this
one could help them predict potential changes
after a powerful storm or tsunami move
through an area.
Exam-style questions
1
a
The littoral zone is the area of a shoreline
that is submerged during high tide and
exposed during low tide.
[1]
Cambridge International AS & A Level Marine Science © Cambridge University Press 2020
CAMBRIDGE INTERNATIONAL AS & A LEVEL MARINE SCIENCE: COURSEBOOK ANSWERS
b
•water cools and minerals fall out
of solution;
Rocky shore:
• exposed to high amounts of erosion
• very little sedimentation
• high wave action
•builds up the chimney of the
hydrothermal vent.
cOrganisms must be adapted to:
Sandy shore:
• less erosion, more sedimentation
•water is moving slower, but still has
wave action
• more gradual slope
[4]
•severe fluctuations in temperature /
high temperatures
[1]
• high pressure
[1]
•presence of toxic chemicals /
H2SO4 in water
[1]
•lack of light preventing
photosynthesis [1]
• no producers
[1]
[Total: 6]
a
Any three of the following:
[Max 3]
•magnetic reversals in the rocks on the
seabed
[Total: 8]
• puzzle-like fit of the continents
4
•fossil evidence of organisms living on
multiple continents
•geological structures on multiple
continents
aAs pressure increases, so do the number
of tube worm larvae that settle. With an
increase of 25 000 kPa, you see an increase
of 533% [((95 – 15) / 15) × 100] in larval
settlement.[2]
• sea-floor spreading
b
[3]
i
tectonic plates slide past one another;
+ abyssal plains / earthquakes /
tsunamis
[2]
ii t ectonic plates move toward each
other;
b•Multiple / specific number of
containers of seawater used.
[1]
•Each container kept at constant
temperature.
[1]
•Each container kept at constant
pressure of 25 000 kPa.
[1]
iii t ectonic plates move away from
each other;
•Different pH levels for each container
provided / within reasonable limits
(for example, container 1 = 7.0 pH,
container 2 = 5.0 pH, container
3 = 3.0 pH).
[1]
+ mid-ocean ridges / hydrothermal
vents / volcanoes
[2]
•Stated number of larvae / 250 larvae
were released into each container. [1]
•Stated number of days (that is,
three days).
+ ocean trenches / volcanoes /
earthquakes / tsunamis
3
[2]
[Total: 9]
a
b
id-ocean ridges along divergent
m
plate boundaries.
Hydrothermal vents form when:
•cold water along the ocean floor sinks
through cracks in Earth’s crust;
•water moves through the crust,
dissolving minerals;
•water forces itself out / escapes through
a vent in the sea floor;
[1]
•Number of larvae that settled
within each container were counted. [1]
•Experiment was repeated three times
and means were calculated for each
container.
[1]
[1]
•magma under crust superheats the
water above;
3
c
Estuaries have protective barriers against
incoming wave action.
[1]
2
[4]
[Max 5]
5
[Total: 7]
a• As Earth rotates;
[1]
•objects moving in a straight line across
Earth’s surface are deflected;
[1]
• deflection is 45°.
[1]
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CAMBRIDGE INTERNATIONAL AS & A LEVEL MARINE SCIENCE: COURSEBOOK ANSWERS
•Northern Hemisphere, objects
deflect to right / Southern
Hemisphere, objects deflect to left. [1]
[4]
b•Coriolis effect changes the
direction of the wind;
[1]
•causes the wind to blow water in
new direction.
[1]
•Northern Hemisphere currents move
in a clockwise direction/ Southern
Hemisphere currents move in a
counterclockwise direction.
[1]
population of phytoplankton increases;
causes an increase in small fish; causes
an increase in marine predators
[4]
cThe waters off Africa will have high
levels of phytoplankton;
the waters off Peru will have low
levels of phytoplankton.
[2]
[Total: 7]
8
a
Plate boundary
Australian Plate –
Pacific Plate
cPossible influences on the shape of
currents include:
• shape of the sea floor;
• changes in temperature;
• changes in salinity;
[2]
• changes in density.
6
any five of:
•tidal range explained as the difference
between the high-tide and low-tide
mark on a shore;
•when Earth, Moon and Sun are in
straight line;
South American Plate
– African Plate
divergent
Pacific Plate – North
American Plate
transform
North American Plate
– Eurasian Plate
divergent
• plates forced against each other
[1]
• idea of building pressure
[1]
•idea of sudden release of energy /
earthquake
[1]
•energy moves large body of water
above plate boundary
[1]
• creates a long-wavelength wave [1]
• causes greater tidal range / spring tide;
•when Moon and Sun are at a right
angle;
•as wave approaches shore, water
becomes shallow
[1]
• forms tsunami
[1]
•gravitational effects are working against
each other, causing weaker tides;
[Max 2]
c Pacific Plate – North American Plate / any
convergent or transform boundary[1]
b
4
convergent
•gravitational effects of the Sun and the
Moon combine and cause stronger tides;
•cause smaller tidal range / neap tides; [5]
7
Boundary type
b•reference to convergent / transform
boundary
[1]
[Total: 8]
a
[4]
Completed Table 2.5:
i during spring tides
[1]
ii
High tide during a spring tide would
push adult horseshoe crabs further up
the shore because:
•it protects eggs while they hatch
from drowning;
•they will hatch at the next spring
tide in two weeks;
•it allows them to hatch very close to
the water line.
[3]
[Total: 9]
a upwelling
[1]
bHigh levels of nutrients brought to
surface; phytoplankton absorbs nutrients;
[Total: 10]
Extended case study questions
1
sunamis move at a greater speed than the
T
average wind-driven wave. Because of a
tsunami’s speed, it can carry great loads of
sediment with it through erosion. As they
slow, the sediment drops quickly depositing
large loads through sedimentation. The weight
of the wave as it recedes helps to compress the
sediments into new rock formations.
2
hile tsunamiite can be found on any shore
W
type, it is more common on sandy shores.
This is due to the amount of sediment present
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CAMBRIDGE INTERNATIONAL AS & A LEVEL MARINE SCIENCE: COURSEBOOK ANSWERS
offshore and the ability of the water to
compress the sediment present on shore.
3
4
5
nswers will vary, but students should give an
A
answer consistent with the idea that the largest
pieces of rock will be on the bottom, while
shells and sand should be in a gradient toward
the highest places in the deposit.
he Atlantic Ocean basin is made of diverging
T
plate boundaries, which rarely give rise to the
earthquakes most commonly linked to the
creation of tsunamis. The Pacific Ocean is
surrounded by convergent plate boundaries,
making it the most tectonically active region
on Earth, causing plenty of the earthquakes
and volcanoes needed to set off a tsunami.
5
nswers will vary based on opinion. Sample:
A
A widespread education plan or posters near
coastlines of what signs you may see that could
indicate a tsunami would be a good alternative,
but often, those signs you would look for may
not appear. So, an education plan may be
helpful, but may also lead to a false sense of
security.
Cambridge International AS & A Level Marine Science © Cambridge University Press 2020