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The 18th International Earth Science Olympiad
Individual Theoretical Test Part 1
ID Number:
Answer Sheet (Do Not Detach)
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Do NOT open the test paper until the invigilator
announces the start of the test.
Test Instructions
1.Exam Duration:The total duration of part 1 is 180 minutes.Once the exam ends,you
must stop writing immediately and wait for the test papers to be collected.
2.Answer Submission:
>All answers must be transferred to the corresponding numbered boxes on the cover
page.Do not exceed the borders of the answer area.
>Only the uppercase letter (A,B,C,etc.)of the correct option should be filled in.
>Even if you mark the correct answer beside the question,you will NOT receive any
points unless it is copied onto the cover page.
>If you need to modify an answer,draw a single line through the original
answer and write the new one in the designated box (e.g.,ABe AB).
Section A:Oceans and the earth systems
The South China Sea is a geologically dynamic and ecologically diverse marginal sea located
at the intersection of multiple tectonic plates and climatic regimes.Bordered by the Asian
continent to the north and west and island arcs to the east and south,it hosts a wide spectrum
of marine environments-from shallow continental shelves to deep-sea trenches and mid-
ocean basins.As shown in Figure A-1,the topography of the South China Sea reveals a broad
continental margin,scattered coral reefs and islands,and a vast abyssal plain reaching depth
beyond 4,000 meters.
Marine processes in the South China Sea reflect the complex interactions among the
lithosphere,hydrosphere,atmosphere,and biosphere.Figure A-2 illustrates a typical
continental margin profile,showing the transition from the coastal plain and shelf to the
continental slope,rise,abyssal plain,and submarine canyons.These structural elements
control sediment distribution and energy gradients across the seafloor.Particularly important
are turbidity currents-dense sediment-laden flows that move rapidly downslope through
submarine canyons,often triggered by storms,earthquakes,or river floods.These flows play a
key role in shaping continental slopes and abyssal fans,and have caused multiple underwater
cable breakages in recent decades.
Figure A-3 shows the vertical stratification of oceanic water masses and benthic zones.The
open sea is broadly defined as the ocean depth where light begins to fade,at an approximate
depth of 200 m or the point of transition from continental shelves to continental slopes.
Conditions within the deep sea are a combination of low temperatures.darkness,and high
pressure.The deep sea is considered the least explored Earth biome as the extreme conditions
make the environment difficult to access and explore.Light penetration,biological activity,
temperature,and pressure vary significantly with depth,affecting both the pelagic ecosystems
and seafloor processes.
In this section,you will explore how topography,sediment dynamics,and water depth interact
to create different depositional and ecological environments across the South China Sea
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