2005 HSC Notes from the Marking Centre Earth and Environmental Science

1. STANSW Meet the Markers 2005 HSC Notes fromthe Marking CentreEarth and Environmental Science David Tweed, Penrith Anglican College d.tweed@pac.nsw.edu.au Fiona Branch, Sydney Grammar, fhb@sydgram.nsw.edu.au

2. General Comments • 1131candidates attempted the Earth and Environmental Science examination. • The most popular electives were Introduced Species and the Australian Environment (76%) and Oceanography (10%).

3. Content • knowledge, understanding and skills developed through the study of discrete sections should accumulate to a more comprehensive understanding than may be described in each section separately • It is important to understand that the Preliminary HSC course is assumed knowledge for the HSC course.

4. Skills 9.1 • at least one question in Section 1 Part B focused on the mandatory skills content in Module 9.1. Candidates who had actively planned and performed practical experiences clearly demonstrated a deeper knowledge and understanding of the content described in this module.

5. Depth of treatment • Candidates need to be reminded that the answer space provided and the marks allocated are guides to the maximum length of response required. • Candidates should use examination time to analyse the question and plan responses carefully, working within that framework to produce clear and concise responses. This may include the use of dot points, diagrams and/or tables, and avoids internal contradictions. This isparticularly so in holistic questions which need to be logical and well structured.

6. Better Responses • Better responses indicate that candidates are following the instructions provided on the examination paper. In these responses, candidates: • show all working where required by the question • do not repeat the question as part of the response • look at the structure of the whole question and note that in some questions the parts follow from each other ie responses in part (a) lead to the required response in part (b) etc • use appropriate equipment, for example, pencils and a ruler to draw diagrams and graphs. (A clear plastic ruler would aid candidates to plot points that are further from the axes and rule straight lines of best fit.)

7. Scaling of EES http://www.uac.edu.au/pubs/pdf/2005-Table-A3.pdf

24. b) Oceanic crust is denser and thinner than continental crust. c) The collision of two plates results in Compressive Forces that cause faulting, folding and metamorphism of rocks

26. 17 a) Pyroclastic flow, Lahar.

27. b) Sumatra is Located near a subduction zone. The subduction of the indo Australian plate beneath Sumatra causes the production of magma due to partial melting. This magma creates the composite volcanoes like Toba.

28. 18 a) Radon gas meters measure the level of radon gas released from faults. An increase in the level of radon detected could indicate an increase in earthquake activity, and thus prove useful in predicting earthquakes.

29. b) Current technology has many problems predicting earthquakes. Improved methods would lead to more accurate early warning systems and evacuation plans decreasing the loss of life and the destruction of infrastructure.

31. 19 Heat generated from the base of the mantle circulates in convection currents. The mantle material becomes less dense and rises when heated. The horizontal motion of the convecting mantle results in friction with the plates producing basal drag. This drives the plates in the direction of the convecting currents. DIAGRAM of convection Cell

33. 20 (a)

34. (b)

36. 21 • BIF’s are sedimentary rocks formed of alternating layers of Iron oxide rich (indicating increasing oxygen levels) and iron oxide poor (indicating low oxygen concentration) high silicate sediments. They indicate fluctuating levels of O2 in the aquatic environment, produced by cyanobacteria. • The O2 released, reacted with the Fe2+ dissolved in the oceans to form FeO which settled on the bottom of the aquatic environment. As the cyanobacteria populations varied so to did the oxygen levels and the consequent FeO levels in the Sediment

37. (b) The media report is unreliable as the Cretaceous environment was highly Oxygenated supporting a wide variety of life forms that used respiration. All the free Fe2+ had precipitated out of the ocean by this stage allowing oxygen to enter the atmosphere, form ozone and allow terrestrial ecosystems to develop.

39. Roots/Rhizoids – would only need small root hairs as they would be mainly used for attachment to some substrate in a swampy environment. a more extensive root system would be required for the absorption of water and nutrients and for anchorage of the plant. Stem – Plant stem in water is buoyed up by the water therefore does not require much structural material. In a terrestrial environment the stem would need to be strengthened by lignin/cellulose for support. Reproduction - Sporangia would release spores into a watery environment. on land, seeds would be needed prevent dessication

40. 23 (a) Oxygen is composed of 2 atoms O2 Ozone is a molecule combining 3 oxygen atoms O3

41. (b) The general trend is a decline in Ozone over 45 years There are many fluctuations over this time The most rapid decline is between 1980 and 1990. The levels seem to be stabilising between 1995 and 2000

42. (c) Montreal protocol – early signs show success as ozone depletion stabilised. Banning of ozone depleting substances (eg CFC Halides, Methyl bromide) used in aerosols, refrigerants, extinguishers. Impact on society increased awareness, finding alternatives impacts upon industry, decrease in skin cancer in the long term. Impact on the environment- Increasing levels of ozone once again, reduction in level of UV reaching the earth. Some replacements for CFCs are greenhouse gases creating/enhancing other problems.

44. Lquid waste (sewage) Filtration (PRIMARY) Grates mesh filters are used to filter out solid larger material as liquid waste passes through Sedimentation (PRIMARY) Liquid waste is placed in tankes and settles. Denser materials accumulate at the bottom known as sludge. Liquid is decanted from the sludge Filtered waste sludge to landfill and fertiliser Nutrient Removal Ponds lagoons are used for algae to absorb the soluble nutrients Sterilisation of waste by UV Addition of chlorine to remove bacteria Aeration Churning of remaining wastes helps remove organic material SECONDARY Bacterial Decomposition Trickled over rocks coated with bacteria. Organic material is removed. SECONDARY Recycled Water Appropriate use of drinking irrigation agriculture environmental flows catchments Sewage treatment is a current method. It involves the primary, secondary and tertiary stages of treatment as detailed below. This is an effective method as it removes all solid wastes, kills bacteria, removes organic material and soluble nutrients. It prevents the growth of algal blooms and eutrophication and is and environmentally friendly process. This along with the fact that the recycled water can be returned to town catchment water supplies used to drink, irrigate or maintain environmental flows makes it an effective method.

46. 25 An environmental flow introduces released dam water back into the environment in cycles. This is important as the introduction of water stimulates breeding /dispersal of some species and ensures biodiversity is maintained. It allows the dispersal of organic material over flood plains which contributes to the soils fertility and maintains plant diversity and health.

48. 26 Soils in the west are vastly older than soils in the east. Soils in the west are also nutrient poor ( less fertile ) compared to the soils in the east. The age of soils affects the amount of weathering and erosion that they have undergone. WA soils have undergone millions of years of leaching depleting them of any nutrients they may have had. Soils in eastern Australia have not gone through as much leaching so have still retained many of their original nutrients. Recent volcanic activity in the east has also lead to the formation and replenishment of basalt derived nutrient rich soil. A lack of volcanic activity of any recency in the west means there has been no replenishment of nutrients via weathering and erosion of basalt.

49. 27 i) A table was used to present the data. It had three columns for name, type and description of the indigenous and non indigenous species in the area

50. (ii) This investigation was best undertaken by a team as we needed a wider knowledge of introduced species for identification. More people gave us a wider knowledge and enabled us to finish the job in a shorter time