science

Ice circle

Ice circle 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 Ice circle rather than just read about it. In short: Ice discs, ice circles, ice pans, ice pancakes or ice crepes are a very rare natural phenomenon that occurs in slow moving water in cold climates. They are thin circular slabs of ice that rotate slowly on a body of water's surface.

Key takeaways

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

Reference excerpt

Ice discs, ice circles, ice pans, ice pancakes or ice crepes are a very rare natural phenomenon that occurs in slow moving water in cold climates. They are thin circular slabs of ice that rotate slowly on a body of water's surface.

Types

Ice discs Ice discs form on the outer bends in a river where the accelerating water creates a force called 'rotational shear', which breaks off a chunk of ice and twists it around. As the disc rotates, it grinds against surrounding ice — smoothing into a circle. A relatively uncommon phenomenon, one of the earliest recordings is of a slowly revolving disc spotted on the Mianus River and reported in an 1895 edition of Scientific American.

Ice pans River specialist and geography professor Joe Desloges states that ice pans are "surface slabs of ice that form in the center of a lake or creek, instead of along the water’s edge". As water cools, ice crystals form into 'frazil ice' and can cluster together into a pan-shaped formation. If an ice pan accumulates enough frazil ice and the current remains slow, the pan may transform into a 'hanging dam', a heavy block of ice with high ridges and a low centre.

Formation

Conditions It is believed that ice circles form in eddy currents. It has been shown that existing ice discs can maintain their rotation due to melting.

Physics Ice circles tend to rotate even when they form in water that is not moving. The ice circle lowers the temperature of the water around it, which causes the water to become denser than the slightly warmer water around it. The dense water then sinks and creates its own circular motion, causing the ice circle to rotate.

Size An unusual natural phenomenon, ice disks occur in slowly moving water in cold climates and can vary in size, with circles more than 15 metres (49 feet) in diameter observed. Ice Circle of Vana-Vigala in Estonia is reported to have had a diameter of over 20 meters, whilst one approximately 298 feet (91 meters) in diameter appeared in Westbrook, Maine in January 2019.

Notable examples

Ice discs have most frequently been observed in Scandinavia and North America. An ice disc was observed in Wales in December 2008 and another one in England in January 2009. An ice disc was observed on the Sheyenne River in North Dakota in December 2013. An ice circle of approximately 15 m (50 ft) in diameter was observed and photographed in Lake Katrine, New York on the Esopus Creek around 23 January 2014. In Idaho, extreme weather led to a rare sighting of an ice disc on the Snake River on 22 January 2014. On 14 January 2019, an ice disc approximately 298 feet (91 metres) wide on the Presumpscot River in Westbrook, Maine, United States drew wide media attention. A smaller disc was reported by park rangers in Baxter State Park, in northern Maine, the same month. In January 2020, an ice disc appeared on the Kennebec River in Skowhegan, Maine, United States In January 2021 a large ice circle was discovered via satellite imagery and on 23 February 2021, an ice disc estimated to be 196–202 metres (643–663 ft) wide was confirmed on the Taltson River, Northwest Territories (just below Tsu Lake). It was estimated to be rotating at approximately 20–25 minutes per rotation.

Artificial ice circles

Artificial ice circles have also been created by cutting a large circle in a sheet of ice. These artificial creations are called "ice carousels". Record setting ice carousels are recorded by the World Ice Carousel Association.

See also Foam line – Accumulations of foam on the surface of freshwater water courses or bodies El Ojo - Rotating floating circular island in Argentina's Paraná Delta, consisting of vegetation and soil

References

Further reading Theories abound on how the river got those patterns – MIT News

External links

Video of ice disc in Germany: "Eisscheibe beim Kunsthof Pösling (Ice slab at Kunsthof Pösling)" (in German). YouTube. 18 January 2009. Archived from the original on 15 December 2021. Retrieved 27 April 2010. Video of ice disc in Ontario, Canada: "Rattray Marsh "Creek Circle"". YouTube. 13 December 2008.

Illustrations

Worked examples

Example 1 — a first encounter with Ice circle

Start with the simplest possible case. Write down what Ice circle 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 Ice circle 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 Ice circle 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 Ice circle

In research: Ice circle 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 Ice circle 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: Ice circle is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bodies of ice, Circles, River morphology, so understanding it makes those chapters shorter.
In everyday life: Look for Ice circle 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 Ice circle in 20 minutes

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

Frequently asked questions

What is Ice circle in simple terms?

Why does Ice circle 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 Ice circle?

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 Ice circle.