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] Cambridge International AS & A Level Marine Science © Cambridge University Press 2020 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 Cambridge International AS & A Level Marine Science © Cambridge University Press 2020 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