earth science

Glacial earthquake

Glacial earthquake 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 Glacial earthquake rather than just read about it. In short: Glacial earthquakes refer to a type of seismic event, with a magnitude of about 5, resulting from glacial calving events. The majority of glacial earthquake activity can be seen in the late summer and are found in Antarctica, Alaska, and Greenland.

Key takeaways

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

Reference excerpt

Glacial earthquakes refer to a type of seismic event, with a magnitude of about 5, resulting from glacial calving events. The majority of glacial earthquake activity can be seen in the late summer and are found in Antarctica, Alaska, and Greenland. About 90% of these occur in Greenland. Glacial earthquakes occur most frequently in July, August, and September in Greenland. Seismographs are analyzed by scientists to identify and locate glacial earthquakes.

Discovery

Since glacial earthquakes produce large amplitude and long period waves that deviate from traditional tectonic earthquake activity, glacial earthquakes require different monitoring methods. This is a primary reason why the specific class of glacial earthquakes was not discovered until 2003. Additionally, glacial earthquakes differ from tectonic earthquakes by lasting longer; for example, a tectonic earthquake with a magnitude of 5 may last 5 seconds, while a glacial earthquake with a magnitude of 5 may last 30 seconds.

Measurement and detection Current and past global seismic data is analyzed using an earthquake detection algorithm explained in a 2006 paper by Goran Ekstrom. The algorithm uses information from seismometers to detect and locate seismic activity by interpreting surface wave propagation and various factors of the seismographs. Glacial earthquake magnitude can be calculated using teleseismic Rayleigh waves amplitudes. Using this method the magnitude ranges from 4.6 to 5.1 MSW.

Causes

Seismic activity is seen in glacial environments due to processes such as stick-slip sliding, and the cracking and falling of ice sheets. A study conducted in 2015 connects this seismic activity to the movement of both ice sheets and the Earth in the event of calving. Calving events occur when ice chunks break off the end of a glacier. When ice chunks break off and fall into the ocean, a large force is generated. This force can last for a couple of minutes and pushes the glacier the ice chunk originated from back and down. This is followed by a rapid rebound. This motion and movement of both ice chunks and Earth material creates signals that alert to glacial seismic activity. Seismic waves are also generated by the Whillans Ice Stream, a large, fast-moving river of ice pouring from the West Antarctic Ice Sheet into the Ross Ice Shelf. Scientists found that each day, two seismic waves are released, each with strength equal to about a magnitude 7 earthquake. It can be seen from the data that in ten minutes the ice river moves about a half-meter and is then still for 12 hours, then moves about a half-meter again. To obtain this data, seismographs were used mostly in Antarctica, and some in Australia, about 6,400 kilometers away.

Global warming

A study done in the early 2000s suggests the number of glacial earthquakes are rising. Using data from January 1993 to October 2005, it was found that more earthquakes were identified each year since 2002 and in 2005, twice as many earthquakes were detected than any other year analyzed. It is possible that this increase could be due to global warming. Glacial earthquakes could be used to better understand rates of ice loss and therefore monitor the severity of global warming. Calving events make up almost half of Greenland's ice sheet's annual mass loss. In 2015, data showed a sevenfold increase in glacial earthquakes in the past twenty years and they have been occurring more in the northern glaciers. This suggests an increase in the rates of ice loss through calving events.

See also Cryoseism Earthquake Glacier Seismometer

References

Illustrations

Worked examples

Example 1 — a first encounter with Glacial earthquake

Start with the simplest possible case. Write down what Glacial earthquake 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 Glacial earthquake 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 Glacial earthquake 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 Glacial earthquake

In research: Glacial earthquake 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 Glacial earthquake 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: Glacial earthquake is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bodies of ice of Greenland, Earthquake stubs, Effects of climate change, so understanding it makes those chapters shorter.
In everyday life: Look for Glacial earthquake 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 Glacial earthquake in 20 minutes

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

Frequently asked questions

What is Glacial earthquake in simple terms?

Why does Glacial earthquake 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 Glacial earthquake?

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 Glacial earthquake.