Anak Krakatau – color images


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To the left – a satellite image from December 17 before the activity

To the right – a satellite image from December 30 – note the large bay in the middle of the left (west) edge. From a certain perspective it probably remarkable that there is anything left above the surface (or below) of the volcano at all.

For bold biologists – there MAY be an opportunity now similar to the situation in the 1930s. It seems likely that Anak Krakatau – if it survives – is largely devoid of plants and animals so recolonization can be observed. Drones should be considered – they are cheap, expendable and do not leave footprints or litter.

Among the challenges – how much danger is there that some or most of the remaining volume will be the basis for another explosion. If any subsequent explosion is less than let’s say VEI=2.5, except for the remaining island possibly disappearing, there might well be no consequences for nearby coastlines. It is not clear, so as to speak, whether the new bay has brought significant amounts of seawater and magma into contact. If not, does a continued west-east fracture present a danger – or in the future would the two ‘halves’ of the island simply crumble peacefully into the sea. Anak Krakatau has been expanding since at least the 1920s – perhaps even right after the 1883 eruption. Note that ash clouds reached 40,000 feet January 2nd so it is worth keeping a close eye on the Sunda Strait. The consensus currently seems to be that the current volcano started from the [submerged] floor of the caldera scooped out in 1883. Of concern would be how stable Cucu Krakatau (Anak = child; Cucu = grandchild) might be if it rises on the remnants of Anak Krakatau.

During the December event ash emissions reached 60,000 ft. The tsunamis struck Tanjung Lesung Beach, Sumur Beach, Teluk Lada Beach, Panimbang Beach, and Carita Beach. I would imagine more locations will be added. The eruption had a volcanic explosivity index (VEI) of 4. So far, the estimates are that the volcano’s height above sea-level went from 338 to 110 meters. The volume of rock displaced is estimated at 150-180 million cubic meters. Currently, the numbers reported are 431 people killed; 7200 injured; 48,000 displaced; 1,600 houses heavily damaged; and over 400 marine vessels damaged. No report yet of any damage to a major ship. It is reasonable to expect all those numbers to increase. There has been no estimate of economic damage so far.

Note that, on average only one eruption per year worldwide has a magnitude of VEI=4 or greater.

Also note that the eruption of August 27, 1883 was far more powerful: more than 18 BILLION cubic meters of ash to a height of 80 km and  a tsunami as high as 30 meters along the west coast of Banten and south coast of Lampung.  The tsunami struck almost 300 villages and killed over 36,000 people. A reasonable guess of the population for Indonesia in 1880 would be 40 million. That means six times as many potential human targets today. The Krakatau complex has a long history of activity – 2017, 2007-12, 2001, 2000, 1999, 1997, 1996, 1994-95, 1992-93, 1988, 1981, 1980, 1979, 1978, 1975, 1972-73, 1969?, 1965?, 1959-63, 1958-59, 1955, 1953, 1952, 1950, 1949, 1946-47, 1946, 1945, 1944, 1943, 1942, 1941, 1938-40, 1937, 1936, 1935, 1932-34, 1931-32, 1927-30, 1883, 1680-81, 1550, 1350, 1150, 1050, 950, 850, 416, 250. 



Indonesian Natural Gas – Historical Numbers



There really is NOT any serious accounting for reserves. Someone provides a seemingly objective estimate of what is thought to be available in a particular area. A casual inventory control analyst would then expect the next year’s reserves to reflection any addition of new gas created and subtraction of gas extracted. Gas extracted would be the sum of gas produced and gas lost or wasted or burned off. Usually, what in seen is that reserves are reported as the same for years and years. When it comes to storage tanks and pipelines the amount of natural gas stored or in transit is usually ignored. In its simplest form production plus imports should roughly equal consumption plus exports. There has been no real effort to distinguish between inventory passing through and inventory to be consumed: for Germany, for example,  if natural gas comes from a pipeline through Poland, regardless of whether the gas is destined for German consumption or is simply headed to Denmark or Belgium, that gas is an import. Likewise, the natural gas than continues on Denmark or Belgium is an export. Here are some historical figures for Indonesia. Note that no (zero) imports were reported


Contemporary LNG carriers


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About 10 years ago Qatar, then the leading exporter of natural gas, designed and ordered a new class of LNG carriers. There are currently 16 Q-Flex ships in service – their figures are about 107,000 dead weight tons (DWT); 137,000 gross tons; 315 meters long; 50 meters wide; 12.5 meter draft; and with a capacity of 210,000 to 216,000 cubic meters (7.6 million cubic feet). These ships were about 50% larger than previous typesal_gattara

At the same time the Q-max class of ships were designed and delivered. There are 14 ships currently active and their figures are 129,000 dead-weight tons (DWT); 133,000 gross tons; 345 meters long; 53 meters wide; 12 meter draft; 266,000 cubic meters (9.4 million cubic feet) capacity.


LNG – Liquefied Natural Gas


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As a brief glance will suggest, there are two essential operations when it comes to processing natural gas: exporting involves cooling the gas the gas to a liquid and then piping it somewhere to be stored or shipped or even consumed for energy while importing involves taking cooled liquid from a ship or other carrier and warming it to a gas. The difference in volumes is about 600:1 (gas to liquid).


The Ghasha (shown above) is a specialized LNG carrier. She was built in 1995 and is 293 meters long; 46 meters wide; and 71,600 tons deadweight with a gross tonnage of 111,000 tons. As of January 3rd, 2019 she is in the Malacca Strait in transit from Japan to the United Arab Emirates.

Indonesia loaded its first LNG cargo at the Bontang plant in East Kalimantan in 1977, and by 1984 Indonesia had overtaken Algeria to become the world’s leading LNG exporter.
In 1988 shipments from Bontang and Arun, the nation’s second liquefaction plant, in 1988 accounted for almost 40% of the global trade in LNG. Indonesian LNG exports peaked in 1999 at over the 28,000,000 tons per year. Indonesia remained the world’s leading LNG supplier until 2006 when it was exceeded by Qatar. Here are the current export rankings in billions of cubic meters – there have been substantial changes in the last decade.


Indonesia – hydrocarbons


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For years the Indonesian government has chronically overspent its budget:  in 2017 the latest budget published had projected more than $130 billion in revenues but more than $160 billion in expenses. It does not appear likely that the national geology budget is making a major contribution to the deficit.

Indonesia produces about 800,000 barrels of crude oil per day. Indonesia exports about 300,000 barrels of crude per day and imports 500,000 barrels per day. At the same time, Indonesia was importing 600,000 barrels of refined petroleum per day and probably producing close to one million barrels of refined petroleum per day. The estimated crude oil reserves are about 3.3 billion barrels. This would be similar in volume to Malaysia  and Yemen and within the top 30 countries of the world (see below). That also means Indonesia can extract crude oil at the present rate for about ten years.


Indonesia produces 72 billion cubic meters of natural gas, consumes 42 billion cubic meters of natural gas and exports the rest. There are very large natural gas reserves claimed – almost 3 trillion cubic meters.



This would be similar in volume to Iraq  and Mozambique and within the top 15 countries of the world (see above). That also means Indonesia can extract natural gas at the present rate for about forty years.

A continuing problem for all countries is that liquid natural gas is expensive and dangerous to store and transport: most of the time if an oil tanker or a refinery has technical challenges crude oil gets spilled. In contrast, natural gas tends to burn.  By virtue of having so many islands, as opposed to being a monolithic landmass, Indonesia has to deal with pipelines, distributed storage and multiple LNG ports.



Bubbles of Methane and Other Gases


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The esteemed Ira Leifer is usually more interested in small steady emissions of methane (=bubbles) because they signal hydrocarbon deposits. I e-asked, “Can the same or similar sensors be used to measure volcanic gas emissions?”

A reasonable estimate is that probably 60% of the gases emitted from a volcano would likely be steam, albeit very hot. Water vapor itself is not that interesting, but what vulcanologists watch for is a persistent change in volume or in proportions of other gases like carbon dioxide, sulfur dioxide and a host of others.

An Australian colleague claims that Indonesia does virtually no (zero) monitoring of volcanic gases. If true,  that does not seem like the best policy for a nation with (depending on how you count) between 76 and 178 active volcanoes. A cynic might describe Indonesia as 18,000 islands with 180 active volcanoes inhabited by 250,000,000 humans many of whom prefer to live on coastlines and near calderas.


To the considerable annoyance of shipping companies there are oil and gas wells in the Sunda Strait. The Sunda Strait is not especially wide – or it would not be a strait. The distance between the southeastern edge of Sumatra and the northwestern edge of Java is barely 30 kilometers. While the strait being narrow and having islanda and getting fairly shallow at the eastern end were somewhat attractive for a bridge project, tides and storms create additional complexities. It is very unclear [to me] whether a large, deep-draft ship would be be influenced by a tsunami moving through the eastern end of the Sunda Strait. I am informed that the USS George Washington [CVN-73] did transit the Sunda Strait July 6, 2011. The narrowest part of the route was 2 kilometers and the shallowest section was 18 meters. The GW’s maximum navigational draft is 37 feet – coupled with a length of 1040 feet at the waterline and a displacement 104,200 long tons that makes for a slow and stressful passage.

I also e-asked, “Would you think there would be any chance that sensors on the marine wells might have detected warning signs?”

Not so-solid geometry of slope collapse (continued)


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Idealized_volcano_top_viewLooking down on an idealized volcano from above. R is the radius of the cone at sea level.  Angle A is portion of the circumference that will slide. In many cases the look-down profile of a volcano is closer to an ellipse than a circle. For example the caldera at Toba on Sumatra to the northwest is roughly an ellipse with a major to minor axis ratio of 3:1 (a circle would be 1:1). A more general solution would be to allow  point collapse to be somewhere in the interior so not necessarily at the center. Likewise, the slope collapse need not start at the peak and extend to the circumference. A key difference is whether the slope collapse exposes the magma to seawater.

The not-so-solid geometry of slope collapse


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H1 = the height above sea-level

H2 = the height from sea-level to the local sea floor

I simplified the model and made the triangle isosceles so the peak angle can be calculated as 180-2 times angle B. It was not obvious that it was worth the bother of making a user enter the two base angles if the triangle was scalene. Part of that was the feeling that what is being represented is not a triangle but rather a cone.  Similarly, the base angles of the trapezoid were taken as equal (forming an isosceles trapezoid) just for simplicity. What really matters is more what the contents and volume of the magma chamber are. The angles do have a mild influence how the collapsing slope falls. A shield volcano could be characterized by gentle upper slopes (about 5o) and somewhat steeper lower slopes (about 10o). Stratovolcanoes have steeper slopes than shield volcanoes, with slopes of 6 to 10o low on the flanks to 30o near the top. Slopes of cinder cones are controlled by the angle of repose (angle of stable slope for loose unconsolidated material) and are usually between about 25 and 35o.


Sunda Strait (Continued)


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The municipal area labelled Tanjungkarang-Telukbetung is more commonly known as Bandar Lampung and can be described as being at the northern end of Lampung Bay.A major tsunami flowing northward from the Sunda Strait would savage the coastal areas in red. The metropolitan area of Bandar Lampung is the capital of the province and has been undergoing rapid population growth. The 2010 census gave a tally of just over 880,000. The 2020 census will likely show between 1,200,000 and 1,300,000. The topology of the bay will funnel the wave and intensify the impact.


Sunda Strait


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Portion of the Sunda Strait between Sumatra (north) and Java (south). The Krakatoa archipelago are the islands in green in the lower right of the upper image and in the upper middle of the lower image. The name Sunda comes from the Indonesian word Pasundan meaning West Java. The people of that area are referred to as Sundanese. The Sunda Strait becomes progressively more shallow as one moves from west to east: the depth is only 20 meters at the eastern end. Even without volcanic eruptions and tsunamis the Sunda Strait is notoriously difficult to navigate due to oil derricks, sandbanks and very strong tidal flows. Virtually all larger modern large ships hauling oil or containers use the Strait of Malacca instead. Fans of World War II military history will recall the Battle of the Sunda Strait on March 1 1942. Australian cruiser HMAS Perth and American cruiser USS Houston encountered an escorted Japanese invasion convoy and were sunk. Some 20 years ago there was quite a lot of work done designing a series of bridges – as far as I am aware the project had been shelved by the current government.