Ice jacking

Key takeaways

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

Reference excerpt

Ice jacking occurs when water permeates a confined space within a structural support or a geological formation, ultimately causing structural fracture when the water freezes and expands. The force from this expansion can damage shorelines, rock faces, and other natural environments. This has the potential to lead to property damage and environmental changes. Ice jacking most commonly refers to shoreline damage caused by lakes freezing, but it has also been applied to geologic engineering and rock erosion. When this occurs within rocks, it is called ice wedging. When this occurs within the soil, it is called frost heaving or ice heaving. It is similar in appearance to, but not to be confused with, ice shove, which is a pile-up of ice on a shoreline.

Lakes and shorelines Ice jacking is a continuous process that occurs during the winter in areas near lakes. The process starts when the ice begins to crack. When water then fills in those gaps, the process repeats and continues until there is a wall of ice surrounding the lake's shoreline, sometimes reaching up to three feet. The extent of ice jacking often depends on temperatures and snow coverage. When there is snow atop the ice, it serves as an insulating layer that helps the ice stay at a constant temperature. When there is no snow, the ice is subject to changing ambient temperatures. Thus, when the temperature decreases, ice not covered by snow will contract, forming cracks that will later be filled in with water from below. When the temperature rises, the ice expands and pushes up towards the shoreline since it has nowhere else to go. More pressure is put on the shoreline as the ice is jacked towards it, often leading to ice ridges or mounds of rock and soil pushed upwards. Ice jacking can provide benefits to a lake ecosystem by trapping nutrients in the ice, creating organic fertilizer. This also creates a buffer zone (a transition between land and aquatic organisms) by fostering plant growth on the shoreline which helps the development of future organisms and can aid in growing fish populations. However, ice jacking is impractical because of the lack of control over the process. There are a few defenses that can fight against ice jacking, such as building a riprap or adding sand to the shoreline, but these defenses have variable outcomes. For example, the riprap could allow the natural process to take place, but there is no guarantee these natural processes would help; they could just as likely repair the damage as leave the affected areas damaged. There are no methods that will prevent damage from ice jacking. Ice jacking can also cause severe property damage, such as occurred on December 17, 2008, at a Gondola tower on Blackcomb Mountain in Whistler, British Columbia. The tower collapsed as the water froze in a splice on the tower, causing structural failure when the water expanded around 2:30 p.m., leaving over fifty passengers stranded in sub-zero temperatures for hours. Following the incident, lift maintenance teams conducted inspections of all other towers to make sure there would be no other occurrence of ice jacking before resuming operation.

Geologic engineering Ice jacking is one form of rock erosion. Ice jacking—because of the water in joints or fissure surfaces within rocks—can cause rock slope failures. This type of failure is progressive, resulting in incremental weakening over time, often requiring several cycles before failure. In a 2005 study, middle-sized rocks (10 to 100,000 m3) in the French subalpine mountain ranges fell from elevations ranging between 200 meters and 2000 meters above sea level. The statistical analysis studied the triggering factors of 46 rockfalls and investigated the rainfall, freeze-thaw cycles, and earthquakes in the region. A correlation was found between slope failure and freeze-thaw cycles, suggesting that ice jacking is a major triggering factor in rockfalls. On December 17, 2008, a Gondola tower on Blackcomb Mountain in Whistler, British Columbia, collapsed due to ice jacking. The splice broke when the water entered a section of the fourth tower and expanded. This occurred around 2:30 PM and left over fifty passengers stranded in sub-zero temperatures for hours. All passengers stuck in cabins on the Excalibur Gondola lift were rescued, with only twelve suffering from mild injuries. Many passengers recall watching in horror as the cars swung sideways, one dangling above the creek. Although some cabins fell, reports state that none of the cabins came off the cable, but that the cable's strength had been significantly compromised. Following the incident, lift maintenance teams conducted inspections of all other towers to ensure no other ice jacking occurrence. After a second inspection by the British Columbia Safety Authority (BCSA), the lift was approved to perform regularly again.

See also Frost weathering – Mechanical weathering induced by freezing water Oxide jacking – Damage to stone caused by the oxidation of embedded metal

References

Worked examples

Example 1 — a first encounter with Ice jacking

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

In research: Ice jacking 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 Ice jacking 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 jacking is common in secondary-school and first-year university syllabi. It links to neighbouring topics Snow or ice weather phenomena, Soil mechanics, Water ice, so understanding it makes those chapters shorter.
In everyday life: Look for Ice jacking 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.

How to study Ice jacking in 20 minutes

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

Frequently asked questions

What is Ice jacking in simple terms?

Ice jacking occurs when water permeates a confined space within a structural support or a geological formation, ultimately causing structural fracture when the water freezes and expands. The force from this expansion can damage shorelines, rock faces, and other natural environments.

Why does Ice jacking 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 Ice jacking?

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 jacking.