earth science

Stokes Magnetic Anomaly

Stokes Magnetic Anomaly 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 Stokes Magnetic Anomaly rather than just read about it. In short: The Stokes Magnetic Anomaly (also known as the Stokes Magnetic Anomaly System, SMAS, New Zealand Junction Magnetic Anomaly, JMA, great Nelson magnetic disturbance, Junction Anomaly, Campbell Magnetic Anomaly System, CMAS) is a magnetic anomaly on the Earth's surface that extends from New Caledonia to the Chatham Rise with complexity consistent with the theory of plate tectonics. History It is named after Captain (la…

Key takeaways

Stokes Magnetic Anomaly 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 Stokes Magnetic Anomaly to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Stokes Magnetic Anomaly from memory before moving on to harder problems.

Reference excerpt

The Stokes Magnetic Anomaly (also known as the Stokes Magnetic Anomaly System, SMAS, New Zealand Junction Magnetic Anomaly, JMA, great Nelson magnetic disturbance, Junction Anomaly, Campbell Magnetic Anomaly System, CMAS) is a magnetic anomaly on the Earth's surface that extends from New Caledonia to the Chatham Rise with complexity consistent with the theory of plate tectonics.

History

It is named after Captain (later Admiral) John Lort Stokes by G. C. Farr in 1916 as he described it first although such naming has proved controversial, hence many of the alternative names. The magnetic declinations were observed by Captain Stokes when captaining HMS Acheron and Commander (later Admiral) Byron Drury in HMS Pandora between 1851 and 1853.

Geology The Stokes Magnetic Anomaly has been characterised for over 3,000 km (1,900 mi) and was essential for understanding the geology of Zealandia as a mainly underwater continent. It extends from 700 km (430 mi) south of New Caledonia to almost the eastern edge of the Campbell Plateau. Over much of its length it has peaks about 30 km (19 mi) to 50 km (31 mi) apart, although this is not the case for much of its New Zealand west coast course. Where the anomaly crosses New Zealand it is displaced by approximately right angle changes in direction for a total of 1,000 km (620 mi) running down the western side of New Zealand from the Northland Peninsula in the North Island to Fiordland but then exiting New Zealand's South Island on its Otago east coast. The Stokes Magnetic Anomaly has been related to magnetic anomaly extending in Australia as the east Lachlan Fold Belt or New England Fold Belt as an extension of where it commences near the western Challenger Plateau and Lord Howe Rise. This gives an age of up to 83 million years before present in its formation but alternatively, it may be extended to represent the earliest ocean crust formed between New Zealand and Marie Byrd Land in Antarctica so could be even older.

References

External links "E Tūhura - Explore Zealandia A portal for geoscience webmaps and information on the Te Riu-a-Māui / Zealandia region". GNS NZ. "Story: Magnetic field". Te Awa: The Encyclopaedia of New Zealand. Retrieved 2022-09-05. "World Digital Magnetic Anomaly Map version 2.0". Retrieved 2022-09-05.

Worked examples

Example 1 — a first encounter with Stokes Magnetic Anomaly

Start with the simplest possible case. Write down what Stokes Magnetic Anomaly 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 Stokes Magnetic Anomaly 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 Stokes Magnetic Anomaly 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 Stokes Magnetic Anomaly

In research: Stokes Magnetic Anomaly 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 Stokes Magnetic Anomaly 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: Stokes Magnetic Anomaly is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geography of New Caledonia, Geography of Oceania, Geography of the New Zealand seabed, so understanding it makes those chapters shorter.
In everyday life: Look for Stokes Magnetic Anomaly 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 Stokes Magnetic Anomaly in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Stokes Magnetic Anomaly 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 Stokes Magnetic Anomaly out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Stokes Magnetic Anomaly in simple terms?

Why does Stokes Magnetic Anomaly 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 Stokes Magnetic Anomaly?

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 Stokes Magnetic Anomaly.