earth science

Indian Ocean Geoid Low

Indian Ocean Geoid Low 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 Indian Ocean Geoid Low rather than just read about it. In short: The Indian Ocean Geoid Low (IOGL) is a gravity anomaly in the Indian Ocean. A circular region in the Earth's geoid, situated just south of the Indian peninsula, it is the Earth's largest gravity anomaly.

Key takeaways

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

Reference excerpt

The Indian Ocean Geoid Low (IOGL) is a gravity anomaly in the Indian Ocean. A circular region in the Earth's geoid, situated just south of the Indian peninsula, it is the Earth's largest gravity anomaly. It forms a depression in the sea level covering an area of about 3 million km2 (1.2 million sq mi), almost the size of India itself. Discovered in 1948 by Dutch geophysicist Felix Andries Vening Meinesz as a result of a ship's gravity survey, it remains largely a mystery. A May 2023 study presented a potential explanation for the weak local gravity through a hypothesis that used computer simulations and seismic data.

Location, characteristics, and formation The gravity anomaly, or "gravity hole", is centered southwest of Sri Lanka and Kanyakumari, the southernmost tip of mainland India, and east of the Horn of Africa. Due to weaker local gravity, the sea level in the IOGL would be up to 106 m (348 ft) lower than the global mean sea level (reference ellipsoid), if not for minor effects such as tides and currents in the Indian Ocean.

Results from numerical models As the Indian plate moved northward after splitting from the Gondwana supercontinent, the Tethys oceanic lithosphere that existed between India and Eurasia sank inside Earth's mantle. As this cold dense Tethys slab reached the bottom of the mantle, it churned the African LLVP (Large Low-Velocity Province), giving rise to mantle plumes of hot low-density material. These buoyant plumes rose to the upper mantle and the low-density material spread underneath the Indian Ocean region, forming the geoid low, according to research published in May 2023. Because of this lower density, the gravitational pull in the IOGL region, the largest gravity anomaly on Earth, is currently measured to be weaker than normal by about 50 mgal (0.005%). The geoid low is believed to have formed around 20 million years ago.

References

Further reading Ghosh, A., Holt, W. E. (17 February 2012). "Plate Motions and Stresses from Global Dynamic Models". Science, 335 (6070): 839–843. doi:10.1126/science.1214209. Ghosh, A., Thyagarajulu, G., Steinberger, B. (16 October 2017). "The Importance of Upper Mantle Heterogeneity in Generating the Indian Ocean Geoid Low". Geophysical Research Letters, 44 (19): 9707–9715. doi:10.1002/2017GL075392. Singh, S., Agrawal, S., Ghosh, A. (10 April 2017). "Understanding Deep Earth Dynamics: A Numerical Modelling Approach". Current Science (Invited Review), 112 (7): 1463–1473. JSTOR 24912692.

Illustrations

Indian Ocean Geoid Low: Approximate collision of Indian Plate into Central Asia — Approximate collision of Indian Plate into Central Asia

Worked examples

Example 1 — a first encounter with Indian Ocean Geoid Low

Start with the simplest possible case. Write down what Indian Ocean Geoid Low 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 Indian Ocean Geoid Low 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 Indian Ocean Geoid Low 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 Indian Ocean Geoid Low

In research: Indian Ocean Geoid Low 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 Indian Ocean Geoid Low 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: Indian Ocean Geoid Low is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geology of the Indian Ocean, Gravimetry, Lowest points, so understanding it makes those chapters shorter.
In everyday life: Look for Indian Ocean Geoid Low 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 Indian Ocean Geoid Low in 20 minutes

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

Frequently asked questions

What is Indian Ocean Geoid Low in simple terms?

Why does Indian Ocean Geoid Low 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 Indian Ocean Geoid Low?

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 Indian Ocean Geoid Low.