earth science

Okinawa Trough

Okinawa Trough is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Okinawa Trough rather than just read about it. In short: The Okinawa Trough (沖縄トラフ, Okinawa Torafu) (also called Chinese: 中琉界沟, literally "China-Ryukyu Border Trough") is a seabed feature of the East China Sea. It is an active, initial back-arc rifting basin which has formed behind the Ryukyu arc-trench system in the West Pacific.

Key takeaways

Okinawa Trough belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Okinawa Trough to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Okinawa Trough from memory before moving on to harder problems.

Reference excerpt

The Okinawa Trough (沖縄トラフ, Okinawa Torafu) (also called Chinese: 中琉界沟, literally "China-Ryukyu Border Trough") is a seabed feature of the East China Sea. It is an active, initial back-arc rifting basin which has formed behind the Ryukyu arc-trench system in the West Pacific. It developed where the Philippine Sea Plate is subducting under the Eurasia Plate.

Description It is a back-arc basin formed by extension within the continental lithosphere behind the far deeper Ryukyu Trench-arc system. The thickness of the crust in the northern Okinawa Trough is 30 km, thinning to 10 km in the southern Okinawa Trough. It has a large section more than 1,000 metres (3,300 ft) deep and a maximum depth of 2,716 metres (8,911 ft). The Okinawa Trough still in an early stage of evolving from arc type to back-arc activity, and features volcanoes such as the Yonaguni Knoll IV.

Implications for the China–Japan maritime boundary

Interpretations

The existence of the Okinawa Trough complicates descriptive issues in the East China Sea. According to Professor Ji Guoxing of the Asia-Pacific Department at Shanghai Institute for International Studies,

China's interpretation of the geography is that "...the Okinawa Trough proves that the continental shelves of China and Japan are not connected, that the Trough serves as the boundary between them, and that the Trough should not be ignored ...." Japan's interpretation of the geography is that "...the trough is just an incidental depression in a continuous continental margin between the two countries ... and that any legal effect of the trough should be ignored ...."

Legal procedure On August 15, 2013, China's mission did a presentation to the Commission on the Limits of the Continental Shelf (CLCS) established under the United Nations Convention on the Law of the Sea (UNCLOS). The presentation was on the proposal that demarcates the limits of the outer continental shelf beyond 200 nm in part of the East China Sea. China states that China's continental shelf in the East China Sea extends to China-Ryukyu Border Trough naturally, which has been over 200 nautical miles away from the mainland baseline of Chinese territorial waters. According to UNCLOS, any country claiming continental shelves beyond 200 nm shall provide relevant scientific evidence to CLCS. To collect solid data, China deployed 14 scientific survey ships, covering an area of 250,000 square kilometers.

Notes

References Taylor, Brian. (1995). Backarc Basins: Tectonics and Magmatism. New York: Plenum Press. ISBN 9780306449376; OCLC 32464941 Thakur, Naresh Kumar and Sanjeev Rajput. (2010). Exploration of Gas Hydrates: Geophysical Techniques. Berlin: Springer Verlag. ISBN 9783642142338 ISBN 3642142338; OCLC 646113755

Illustrations

Worked examples

Example 1 — a first encounter with Okinawa Trough

Start with the simplest possible case. Write down what Okinawa Trough claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Okinawa Trough before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Okinawa Trough ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Okinawa Trough

In research: Okinawa Trough appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Okinawa Trough in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Okinawa Trough is common in secondary-school and first-year university syllabi. It links to neighbouring topics Back-arc basins, Geology of China, Geology of Japan, so understanding it makes those chapters shorter.
In everyday life: Look for Okinawa Trough outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Okinawa Trough in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Okinawa Trough means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Okinawa Trough out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Okinawa Trough in simple terms?

Why does Okinawa Trough matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Okinawa Trough?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Okinawa Trough.