earth science

Myōjin-shō

Myōjin-shō 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 Myōjin-shō rather than just read about it. In short: Myōjin-shō (明神礁) is a submarine volcano located about 450 kilometers south of Tokyo on the Izu-Ogasawara Ridge in the Izu Islands. Volcanic activity has been detected there since 1869.

Key takeaways

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

Reference excerpt

Myōjin-shō (明神礁) is a submarine volcano located about 450 kilometers south of Tokyo on the Izu-Ogasawara Ridge in the Izu Islands. Volcanic activity has been detected there since 1869. Since then it has undergone more eruptions, the most powerful of which resulted in the appearance and disappearance of a small island. The name Myōjin-shō derives from a fishing boat, No.11 Myōjin-Maru of Yaizu City, Shizuoka Prefecture, the crew of which first witnessed the major volcanic eruption of 1952. Myōjin itself refers to 'shining deity' or 'illuminating deity' in reference to the Kami.

Eruption of 1952-1953

The volcanic eruption from 1952 to 1953 was one of its biggest eruptions on record, with the repetitious appearance and disappearance of an island, which at one point reached over ten metres above sea level, before sinking after a major volcanic eruption in September 1953. On September 24, 1952, a survey vessel, Kaiyo Maru No. 5 of the Hydrographic Department of the Maritime Safety Agency, was destroyed by the volcano, with the loss of its crew of 31 (including the nine scientists studying the eruption). Consequently, the Department developed Manbou (Sunfish), an unmanned radio operating survey boat, and has used it for the research of dangerous sea areas such as submarine volcanoes. The eruption was the first correlation of strong, unusual signals in the SOFAR channel recorded on September 18, 1952 at the Navy's California SOFAR stations at Point Sur and Point Arena with a volcanic eruption. The station at Kaneohe, Hawaii had not detected the signals indicating its source was west of 180º with a line of position obtained from the two California stations passing through a point about 200 nautical miles south of Tokyo. News reports of the volcano's violent eruption focused attention on the details and an effort to precisely time the volcano's activity by the recordings at the SOFAR stations. By doing so the activity was detailed and the most likely time Kaiyo Maru No. 5 was destroyed.

Survey of 1998-1999 In 1998 and 1999, the Hydrography Department conducted comprehensive sea bottom surveys around Myōjin-shō, using the state-of-the-art survey vessel Shoyo and Manbou II, the second generation Manbou. As a result of these surveys, a detailed picture of the seabed topography around Myōjin-shō was made for the first time. Manbou II conducted the survey of the sea area within a radius of 3 nautical miles (about 5.4 kilometers) of Myōjin-shō. Shoyo conducted the survey of the sea area within a radius of about 10 nautical miles (about 18.5 kilometers) but farther than the area of the radius of 3 nautical miles (5.6 km). Manbou II works by the order of preprogrammed instructions and measures depth and water temperature. Bathymetric survey of Manbou II was carried out by using the "PRD-601" echo sounder at intervals of 0.2 nautical miles (about 370 meters). Shoyo conducted a comprehensive survey including the geological and geophysical surveys of sea bottom. Bathymetric survey of Shoyo was carried out by using a "Seabeam 2112" echo sounder at intervals of 0.5 nautical miles (about 930 meters).

Structure Previously, Myōjin-shō was considered to be the central cone of a double volcano with the Bayonnaise Rocks (rocks of 9.9 meters in height above the sea level) as a portion of the somma (Mita, 1949). As a result of the survey, however, the authors found that both Myōjin-shō and the Bayonnaise Rocks are cones on the somma of a double volcano. The foot of this double volcano lies 1,400 to 1,500 meters in depth and the size is about 30 by 25 kilometers east-west, north-south. The somma is almost a circle in the diameter of 7 by 9 kilometers and the height is 1,000 – 1,400meters. The diameter of the caldera floor is 5.6 kilometers and about 1,100 meters in depth. The central cone is a height formerly known as Takane-shō, 328 metres below sea level. Myōjin-shō is a post caldera cone formed in the northeastern part of the somma of the double volcano. It is a single conical cone and its height is 550 meters with the shallowest depth 50 meters. A record that suggests a gushing of bubbles near the summit was obtained and micro-earthquakes were observed near Myōjin-shō, showing that the volcano is still active, although at a low level

Gallery

1952 eruption

References

External links Survey of Myojin-sho LIFE Oct 13, 1952, "Birth and Death of a Volcano"

Illustrations

Worked examples

Example 1 — a first encounter with Myōjin-shō

Start with the simplest possible case. Write down what Myōjin-shō 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 Myōjin-shō 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 Myōjin-shō 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 Myōjin-shō

In research: Myōjin-shō 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 Myōjin-shō 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: Myōjin-shō is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1952 in Japan, 1952 natural disasters, Ephemeral islands, so understanding it makes those chapters shorter.
In everyday life: Look for Myōjin-shō 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 Myōjin-shō in 20 minutes

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

Frequently asked questions

What is Myōjin-shō in simple terms?

Myōjin-shō (明神礁) is a submarine volcano located about 450 kilometers south of Tokyo on the Izu-Ogasawara Ridge in the Izu Islands. Volcanic activity has been detected there since 1869.

Why does Myōjin-shō 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 Myōjin-shō?

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 Myōjin-shō.