science

Sheeted dyke complex

Sheeted dyke complex is a 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 Sheeted dyke complex rather than just read about it. In short: A sheeted dyke complex, or sheeted dike complex, is a series of sub-parallel intrusions of igneous rock, forming a layer within the oceanic crust. At mid-ocean ridges, dykes are formed when magma beneath areas of tectonic plate divergence travels through a fracture in the earlier formed oceanic crust, feeding the lavas above and cooling below the seafloor forming upright columns of igneous rock.

Key takeaways

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

Reference excerpt

A sheeted dyke complex, or sheeted dike complex, is a series of sub-parallel intrusions of igneous rock, forming a layer within the oceanic crust. At mid-ocean ridges, dykes are formed when magma beneath areas of tectonic plate divergence travels through a fracture in the earlier formed oceanic crust, feeding the lavas above and cooling below the seafloor forming upright columns of igneous rock. Magma continues to cool, as the existing seafloor moves away from the area of divergence, and additional magma is intruded and cools. In some tectonic settings slices of the oceanic crust are obducted (emplaced) upon continental crust, forming an ophiolite.

Geometry

The individual dykes typically range in thickness from a few centimetres to a few metres. Most of the dykes show evidence of one-sided chilled margins, consistent with most dykes having been split by later dykes. It is also common for the chilled margins to be consistently on one side, suggesting that most dykes in any one exposure were gradually moved away from the spreading centre by further stages of intrusion in a constant location. The layer of sheeted dykes that makes up the lower part of Layer 2 of the oceanic crust is typically between one and two kilometres thick. At the top, the dykes become increasingly separated by screens of lava, while at the base they become separated by screens of gabbro.

Dyke formation

Sheeted dyke complexes are most commonly found at divergent plate boundaries marked by the presence of mid-ocean ridges. These subaqueous mountain ranges are made up of newly created oceanic crust due to tectonic plates moving away from each other. In response to the separation of plates, magma from the asthenosphere is subject to upwelling, pushing hot magma up towards the seafloor. The magma that reaches the surface is subject to fast cooling and creates basaltic formations such as pillow lava, a common extrusive rock created near areas of volcanic activity on the seafloor. Although some magma is able to reach the surface of oceanic crust, a considerable amount of magma solidifies within the crust. Dykes are formed when the rising magma that does not reach the surface cools into upright columns of igneous rock beneath areas of divergence.

Ophiolites Dykes are perpetually formed as long as magma continues to flow through the plate boundary, creating a distinct, stratigraphic-like sequences of rocky columns within the seafloor. Ophiolites are formed when these sections of oceanic crust are revealed above sea level and embedded within continental crust.

Seafloor spreading and continental drift

The creation of sheeted dykes is a perpetual and continuous process that promotes the phenomenon known as seafloor spreading. Seafloor spreading is the creation of new oceanic crust by volcanic activity at mid-ocean ridges, and as magma continues to rise and solidify at mid-ocean ridges, the existing older dykes are pushed out of the way to make room for newer seabed. The rate at which new oceanic crust is created is referred to as spreading rate, and variations in spreading rate determine the geometry of the mid-ocean ridge being created at plate boundaries.

Fast-spreading ridges Mid-ocean ridges with a spreading rate greater than or equal to 90 mm/year are considered to be fast-spreading ridges. Due to the large amounts magma being expelled from the asthenosphere in a relatively short period of time, these formations typically protrude much higher from the seafloor.

Slow-spreading ridges Mid-ocean ridges with a spreading rate less than or equal to 40 mm/year are considered to be slow-spreading ridges. These formations are typically characterized by a large depression in the seafloor, known as rift valleys, and are formed due to the lack of magma present to solidify.

Examples Troodos Ophiolite, Cyprus Maydan Syncline, Oman, part of the Semail Ophiolite - A sheeted dyke complex on the coast of Oman has been discovered to have been formed during a single sea-floor spreading episode. Hole 504b, Costa Rica - Hole 504b is a scientific ocean drilling program that burrowed 1562.3 m below the seafloor directly through layers of sediment exposing sheeted dykes and pillow lava.

References

Illustrations

Worked examples

Example 1 — a first encounter with Sheeted dyke complex

Start with the simplest possible case. Write down what Sheeted dyke complex claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In 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 Sheeted dyke complex 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 Sheeted dyke complex 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 Sheeted dyke complex

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

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

Frequently asked questions

What is Sheeted dyke complex in simple terms?

Why does Sheeted dyke complex matter?

Because it connects several 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 Sheeted dyke complex?

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 Sheeted dyke complex.