earth science

Killas

Killas 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 Killas rather than just read about it. In short: Killas is a Cornish mining term for metamorphic rock strata of sedimentary origin which was altered regionally by the Variscan orogeny and then locally by heat from the intruded granites in the English counties of Devon and Cornwall. The term is used in both counties.

Key takeaways

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

Reference excerpt

Killas is a Cornish mining term for metamorphic rock strata of sedimentary origin which was altered regionally by the Variscan orogeny and then locally by heat from the intruded granites in the English counties of Devon and Cornwall. The term is used in both counties.

Etymology "Killas" first appeared in print in 1674 as "kellus". As a Cornish place name element, kellys is found in Porkellis where it means 'lost' or 'hidden' (a passive-participle), but its etymology as Cornish dialect is unknown. The reconstructed proto-Celtic verb *kel-o- from the PIE *4k̑el- also means 'to hide'.

Petrogenesis The deposition of the killas strata occurred during the Devonian and Carboniferous geological periods. The sediments are not evenly spread over the county, with the Carboniferous beds only found in the north of Cornwall. The depositional environments of the killas were very varied, as is revealed by the fossil content and the sedimentary sequences. The fossils indicate changes from anaerobic, deep ocean-basin environments to shallow sea environments. The deformed brachiopod fossil Cyrtospirifer verneuili, known to quarrymen as the Delabole Butterfly, was found in the upper Devonian beds of North Cornwall. Shortly after the deposition of the sediments, the Variscan orogeny caused low grade regional metamorphism of the sediment followed by the intrusion of the Cornubian batholith and the subsequent contact metamorphism created the metamorphic rocks seen today. The orogeny put intense pressure on the sediments causing them to be folded and faulted. This is most apparent in the cliffs at Millook Haven on the north Cornwall coast, where the cliffs display an impressive series of recumbent angular folds.

Economic uses Killas underlies two thirds of Cornwall and on and around Dartmoor in Devon, and, as a result of hydrothermal mineralization from the granites, contain the majority of the mineral lodes or veins which at one time provided up to half of the world's tin and copper, and economic prosperity to Cornwall (and to a lesser extent Devon). Of lesser economic importance, the stone itself is an important building stone, while locally, in the Delabole to Tintagel region, there are good quality roofing slates with the largest single source in the county being Delabole slate quarry, which has provided a high quality stone for at least six centuries.

Illustrations

Worked examples

Example 1 — a first encounter with Killas

Start with the simplest possible case. Write down what Killas 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 Killas 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 Killas 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 Killas

In research: Killas 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 Killas 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: Killas is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geology of Cornwall, Geology of England, Metamorphic rocks, so understanding it makes those chapters shorter.
In everyday life: Look for Killas 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 Killas in 20 minutes

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

Frequently asked questions

What is Killas in simple terms?

Why does Killas 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 Killas?

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 Killas.