ACJC Prelim H2 GEO P1 ans

© ACJC Prelims 2016 H2/9730/01 1 ANGLO-CHINESE JUNIOR COLLEGE JC 2 Preliminary Examinations 2016 GEOGRAPHY 9730/01 Higher 2 Paper 1 Physical Geography Time: 3 hours 19 August 2016 (Friday) READ THESE INSTRUCTIONS FIRST Write your Centre number, index number and name on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all questions. Section B Answer two questions, each from a different topic. Insert 1 contains all the Figures and Table referred to in the question paper. Diagrams and sketch maps should be drawn whenever they serve to illustrate an answer. The world outline map may be annotated and handed in with relevant answers. You are reminded of the need for good English and clear presentation in your answers. The number of the marks is given in brackets [ ] at the end of each question or part question. Bundle your answers for Section A and those for Section B separately – i.e. you should have two bundles – one for Section A and one for Section B. On the cover sheet provided, include:  Your name and index no.  The question numbers of the question you have attempted in the boxes provided, and place the cover sheet as the top page over your answers to Section A. This document consists of 5 printed pages, including this cover page. Insert consists of 10 printed pages. Department of Geography Anglo-Chinese Junior College 25 Dover Close East Singapore 139745 [Turn Over

© ACJC Prelims 2016 H2/9730/01 2 Section A Answer all the questions in this section. Question 1, 2 and 3 carry 12 marks and Question 4 carries 14 marks. You should allocate your time accordingly. Lithospheric Processes, Hazards and Management 1. Fig. 1A shows a cross section through the plate boundary where the North American and Caribbean plates meet. Figs. 1B and 1C show information about the volcanic eruption of the Soufriere Hills on the Caribbean volcanic island arc of Montserrat (a LDC). (a) Describe and explain the major tectonic processes operating in the development of the volcanic island arc of Montserrat in Fig. 1A. o The volcanic island arc of Montserrat is located along the destructive plate boundaries – where the heavier oceanic North American plate subducts under the lighter Caribbean plate. o As the North American plate is being subducted, a trench is formed first at the interface with the adjoining slab as the descending plate plunges under the overriding plate, the edges of the two plates will come under tremendous amount of stress and pressure. o The compressional forces at convergent subduction plate boundaries cause the sediment of the accretionary wedge to be intensely folded and faulted. o Frictional drag induced by the subduction, together with heat from conduction from the hotter lithosphere at depth, creates conditions of lower temperatures and high pressures , and alters or metamorphoses the local rocks, including that of the oceanic crust and the sediments of the accretionary wedge. This type of metamorphism is termed as blueschist metamorphism. o The subducting basaltic ocean crust contains hydrous minerals like amphiboles, some of which are formed by hydrothermal alteration as seawater seeped through hot, fractured, young ocean crust at the mid-ocean ridge – seafloor metamorphism. o As the oceanic plate sinks deeper into the mantle the pressure and temperature in crease, and at 100 -200 km below the surface, metamorphic dewatering process (dehydration) liberates water from the descending crust. o The hot fluids gradually seep upward into the overlying wedge of hot mantle. The addition of water to the already hot man tle rocks lowers their melting temperature resulting in partial melting of ultramafic mantle rocks to yield mafic (basic) magma. o The result is a magma which is a hybrid of the different sources of [5]

© ACJC Prelims 2016 H2/9730/01 3 material derived from oceanic sediments, oceanic crust, an d upper mantle. o The newly-formed magma created in this manner is less dense than the surrounding mantle rocks and will slowly rise. Through the rise, the magma undergoes further alteration as it reacts with the overlying crust alongside with fractional crystallization. o Ferromagnesium minerals which have higher melting points will crystallise (solidify) at earlier and at greater depths, and the rest of the molten magma which ascends will progressively have lower ferromagnesium content, and comparatively, h igher silica content, making it more acidic (felsic) than basic (mafic) in its mineral constituent. The higher the silica content , the more viscous the lava, and the more explosive the eruption will be – andesitic magma is formed. o the rising magma (which i s usually andesitic in composition) will be emplaced in the overriding oceanic crust (mafic in mineral composition) where it will cool and crystallize and when they go above the water surface, volcanic island arcs like Montserrat will be formed. Volcanoes of the volcanic island arc tend to be made up of andesitic rocks o Forms strato-volcanoes or composite cones/volcanoes (b) Using evidence from Figs. 1A, 1B and 1C, explain the nature of three volcanic hazards associated with the eruption of the Soufriere Hills. o Fig. 1A: Pyroclastic flows – dense mixtures of fluidized hot rock fragments, lava particles and ash buoyed up by hot gases , containing as much as 80% of unconsolidated material. The flow is fluidized because it contains water and gas from the eruption. Very high temperature. o Fig. 1B: Lava flows – streams of molten rock that pour or ooze from an erupting vent. In this case, the lava flows are more likely to be viscous andesitic lava. o Fig. 1C: Lahar (due to the presence of rivers shown in Fig. 1C) – a hot or cold mixture of water and rock fragments flowing down the slopes of a volcano and/or river valleys. When moving, a lahar looks like a mass of wet concrete that carries rock debris ranging in size from clay to boulders more than 10 m in diame ter. Also known as volcanic mudflow. May develop when the pyroclastic materials fall into and mix with the rivers. [3]

© ACJC Prelims 2016 H2/9730/01 4 (c) Using evidence from Figs. 1B and 1C, explain why people living on Montserrat found it hard to manage the effects of this volcanic eruption. Fig. 1B: o “This was the first recorded eruption of this volcano.” – not expecting and hence may not have been predicted. o May not be prepared as they have no previous experience of managing the effects of volcanic eruption o “On July 18th 1995, Soufriere Hills, a volcano on the Caribbean island of Montserrat began erupting. The volcano was still hissing and rumbling in October 1997.” – the volcano continued to erupt for over two years. o Destruction of over 80% of the buildings and the capital c ity, Plymouth affected – most important buildings might have been affected. Fig. 1C: o Agriculture land might be affected – affecting the growth and production of cotton and fruits – affecting availability of food and business o A small island pf 102 square km so a large proportion was affected o Difficulty in receiving aid [4] Atmospheric Processes, Hazards and Management 2. Fig. 2 A shows the locations of three cities in Africa while Fig. 2B shows the climographs of these cities. Fig. 2C shows the global impact of El Niño 1997-98. (a) Describe and account for the climatic characteristics shown in the climographs of three cities in Fig. 2B. Gao: o Lowest total annual pr