earth science

Lau–Colville Ridge

Lau–Colville Ridge 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 Lau–Colville Ridge rather than just read about it. In short: The Lau–Colville Ridge is an extinct oceanic ridge located on the oceanic Australian Plate in the south-west Pacific Ocean extending about 2,700 km (1,700 mi) from the south east of Fiji to the continental shelf margin of the North Island of New Zealand. It was an historic subduction boundary between the Australian Plate and the Pacific Plate and has important tectonic relationships to its east where very active spr…

Key takeaways

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

Reference excerpt

The Lau–Colville Ridge is an extinct oceanic ridge located on the oceanic Australian Plate in the south-west Pacific Ocean extending about 2,700 km (1,700 mi) from the south east of Fiji to the continental shelf margin of the North Island of New Zealand. It was an historic subduction boundary between the Australian Plate and the Pacific Plate and has important tectonic relationships to its east where very active spreading and subduction processes exist today. It is now the inactive part of an eastward-migrating, 100 million year old Lau-Tonga-Havre-Kermadec arc/back-arc system or complex and is important in understanding submarine arc volcanism because of these relationships. To its west is the South Fiji Basin whose northern bedrock is Oligocene in origin.

Geography

It is divided into two segments as the ridge is flanked on its eastern side by two southward propagating back-arc basins, the northern Lau Ridge (called historically the South Fiji Ridge and also known as the Fiji Ridge, Neckes Ridge and Southern Fiji Ridge) that forms the western boundary of the Lau Basin and has contributed to many islands south east of Fiji. The Lau Basin to its east currently contains 6 million year old active spreading centers between the Australian and Niuafo'ou or Tonga microplates. The southern Colville Ridge (also known as Khrebet Kolvil-Lau from Russian Хребет Колвил-Лау)forms the western boundary of the Havre Trough. The Havre Trough has had rift extension for the last 2 million years between the Australian plate and the Kermadec microplate and this extends into Zealandia's continental Taupō Rift and New Zealand's Taupō Volcanic Zone.

Geology The remnant andesitic volcanic arc Lau Ridge was mainly active between 14 and 6 million years ago although late volcanism persisted until 2.5 million years ago. The Colville Ridge has been found to have volcanics aged between 7.5 to 2.6 million years ago. The composition range is from mafic picro-basalt to dacite with arc-type element patterns intermediate between Pacific mid ocean ridge basalt and subducted lithosphere. The South Fiji Basin to the west of the Lau–Colville Ridge contains back‐arc basin basalts up to 33 million years old that were erupted during spreading and some ocean island like basalts erupted several million years after spreading ceased in the basin which was before 22 million years ago Directly to the east of the ridge in its central portion the Lau basin contains an area of sediment that has been called the Western Sedimentary Basin. The sediments in the Havre Trough can be up to 1.5 km (0.93 mi) thick.

Tectonics The late Miocene rifting of about 6 million years ago initiated in what was an old forearc (called the Vitiaz Arc) and was in Cretaceous-Eocene arc crust that became part of the northern Lau Ridge. Currently back-arc spreading to the east of the Lau Ridge in the adjacent Lau Basin occurs along a number of spreading centers and the Valu Fa Ridge (VFR). As we come south down the Lau Basin spreading rates decrease being for the Central Lau Spreading Centre (CLSC) 120 mm (4.7 in)/year, just above Eastern Lau Spreading Center (ELSC) 102 mm (4.0 in)/year, at the start of the Valu Fa Ridge (VFR) to the south 69 mm (2.7 in)/year, and at its southern end 48 mm (1.9 in)/year, consistent with the southward propagation previously mentioned. These spreading centers have now partially dismembered the Lau Ridge. To the south it is now thought seafloor spreading at the Havre Trough started about 5.5–5.0 million years ago in response to the rollback of the subducting Pacific Plate and terminated abruptly about 3.0–2.5 million years ago, perhaps explaining the long noted lack of a mid oceanic ridge structure but rather rift like subsidance.

Worked examples

Example 1 — a first encounter with Lau–Colville Ridge

Start with the simplest possible case. Write down what Lau–Colville Ridge 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 Lau–Colville Ridge 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 Lau–Colville Ridge 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 Lau–Colville Ridge

In research: Lau–Colville Ridge 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 Lau–Colville Ridge 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: Lau–Colville Ridge is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geography of the New Zealand seabed, Geology of Zealandia, Seismic zones of Oceania, so understanding it makes those chapters shorter.
In everyday life: Look for Lau–Colville Ridge 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 Lau–Colville Ridge in 20 minutes

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

Frequently asked questions

What is Lau–Colville Ridge in simple terms?

Why does Lau–Colville Ridge 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 Lau–Colville Ridge?

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 Lau–Colville Ridge.