chemistry

Geochemical cycle

Geochemical cycle is a chemistry 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 Geochemical cycle rather than just read about it. In short: In Earth science, a geochemical cycle is the pathway that chemical elements undergo to be able to interact with the reservoirs of chemicals in the surface and crust of the Earth. The term "geochemical" tells us that geological and chemical factors are all included.

Key takeaways

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

Reference excerpt

In Earth science, a geochemical cycle is the pathway that chemical elements undergo to be able to interact with the reservoirs of chemicals in the surface and crust of the Earth. The term "geochemical" tells us that geological and chemical factors are all included. The migration of heated and compressed chemical elements and compounds such as silicon, aluminium, and general alkali metals through the means of subduction and volcanism is known in the geological world as geochemical cycles. The geochemical cycle encompasses the natural separation and concentration of elements and heat-assisted recombination processes. Changes may not be apparent over a short term, such as with biogeochemical cycles, but over a long term changes of great magnitude occur, including the evolution of continents and oceans.

Differentiating biogeochemical cycles Some may use the terms biogeochemical cycle and geochemical cycle interchangeably because both cycles deal with Earth's reservoirs. However, a biogeochemical cycle refers to the chemical interactions in surface reservoirs such as the atmosphere, hydrosphere, lithosphere, and biosphere whereas a geochemical cycle refers to the chemical interactions that exist in crustal and sub crustal reservoirs such as the deep earth and lithosphere.

Earth system The Earth, as a system, is open to radiation from the sun and space, but is practically closed with regard to matter. As all closed systems, it follows the law of conservation of mass which states that matter cannot be created nor destroyed, thus, the matter, although transformed and migrated, remains the same as when the Earth was formed. The Earth system contains seven different reservoirs that are separated into surface reservoirs, which include atmosphere, hydrosphere, biosphere, pedosphere, and lithosphere and the isolated reservoirs that include deep Earth and outer space. Geochemical cycles are concerned with the interactions between deep earth which consists of Earth's mantle and core, and the lithosphere which consists of the Earth's crust.

Pathways Flux in geochemical cycles is the movement of material between the deep Earth and the surface reservoirs. This occurs through two different processes: volcanism and subduction of tectonic plates. Subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate and sinks into the mantle as the plates converge. This leads to the sinking of one plate into the mantle which creates a broad range of geochemical transformations or cycling. Volcanism is the process that takes place at divergent boundaries by which one tectonic plate separates from another creating a rift in which molten rock (magma) erupts onto the surface of the Earth. This molten rock magma then cools and crystallizes, forming igneous rocks. If crystallization occurs at the Earth's surface, extrusive igneous rocks are formed; if crystallization occurs within the Earth's lithosphere, intrusive igneous rocks are formed which can then be brought to Earth's surface by denudation

Important cycles Categories and examples of geochemical cycles:

Illustrations

Worked examples

Example 1 — a first encounter with Geochemical cycle

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

In research: Geochemical cycle appears in chemistry 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 Geochemical cycle 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: Geochemical cycle is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geochemistry, so understanding it makes those chapters shorter.
In everyday life: Look for Geochemical cycle 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Geochemical cycle in 20 minutes

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

Frequently asked questions

What is Geochemical cycle in simple terms?

Why does Geochemical cycle matter?

Because it connects several chemistry 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 Geochemical cycle?

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 Geochemical cycle.