earth science

Ring dike

Ring dike 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 Ring dike rather than just read about it. In short: A ring dike or ring dyke is an intrusive igneous body that is circular, oval or arcuate in plan and has steep contacts. While the widths of ring dikes differ, they can be up to several thousand meters.

Key takeaways

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

Reference excerpt

A ring dike or ring dyke is an intrusive igneous body that is circular, oval or arcuate in plan and has steep contacts. While the widths of ring dikes differ, they can be up to several thousand meters. The most commonly accepted method of ring dike formation is directly related to collapse calderas.

Caldera collapse and ring dike formation

Collapse calderas form due to the emptying of a magma chamber. Effusive eruptions that take place on the flanks of the associated volcano and a fissure system that direct magma away from the chamber are both mechanisms that can empty a magma chamber. As pressure in the magma chamber changes, an increase in tensile stresses create tension fractures at the surface of the volcano. The geometry of the top of the magma chamber dictates the location and magnitude of the tension fractures. In addition, it was found that the higher the radius to depth ratio of the magma chamber, the higher the probability of forming a collapse caldera. Once a tension threshold is approached, the roof of the magma chamber collapses in on itself, and is known as cauldron subsidence. Tension fractures extend deeper in the profile and shear fractures or dip-slip faults form in a circular pattern around the caldera and are known as ring faults. Ring faults can be either vertical or steeply dipping faults. When they are inward dipping, they are known as normal faults and when they are outward dipping they are known as reverse faults. Ring faults then allow magma to rise through the fractures, forming a ring dike. These dikes can form as a direct result of collapse caldera formation, or through many injections around the ring fault over time. The magma of a ring dike is typically composed of acidic or intermediate composition due to the less dense melt that exists at the top of the magma chamber.

Another mechanism of ring dike formation It has been hypothesized that ring dikes may form when inclined sheets are captured within a ring fault system, which cause them to act as feeder dikes. The deflection of the sheets may be caused by the difference in material properties between and within the fault zone.

Implications Whether or not a caldera ring fault dips inward or outward from the center of subsidence is a highly contentious issue. Ring faults near the surface are subject to erosion and mass wasting, changing the morphology of the caldera walls and making it difficult to tell the dip of the fault at formation.

Examples

Ossipee ring-dike complex About 36 ring dikes have been found in the Ossipee Mountains in New Hampshire. Caldera subsidence appears to be the mechanism leading to the formation of some of the ring dikes, but not all of them. The composition ranges from monzonite to quartz syenite.

Loch Bà ring dike The Loch Bà ring dike, found on the Isle of Mull in Scotland, serves as a classic example of a well formed ring dike. This intrusive body forms an oval and its diameter can be measured at roughly 5.8 km by 8.5 km. The width of the dike varies throughout the profile, with a maximum width of approximately 300 meters. The composition varies from rhyolite to felsite, with phenocrysts of alkali feldspar and mafic minerals.

Pilanesberg Alkaline Ring Complex The Pilanesberg Alkaline Ring Complex in South Africa is considered one of the largest alkaline ring complexes in southern Africa. The structure consists of multiple concentric intrusive phases associated with ring-dike emplacement and caldera-style subsidence. The complex has been extensively studied as an example of Proterozoic intraplate magmatism and alkaline igneous activity.

See also Batholith Cone sheet Fissure vent Laccolith

References

Illustrations

Worked examples

Example 1 — a first encounter with Ring dike

Start with the simplest possible case. Write down what Ring dike 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 Ring dike 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 Ring dike 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 Ring dike

In research: Ring dike 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 Ring dike 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: Ring dike is common in secondary-school and first-year university syllabi. It links to neighbouring topics Igneous petrology, Ring dikes, Volcanology, so understanding it makes those chapters shorter.
In everyday life: Look for Ring dike 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 Ring dike in 20 minutes

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

Frequently asked questions

What is Ring dike in simple terms?

Why does Ring dike 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 Ring dike?

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 Ring dike.