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Saturday, 17 March 2012

High Resolution Satellite Image Of "Mohorovicic Discontinuity"...What The Hell Is The "Moho" Anyway?

 A commemorative plaque of Andrija Mohorovičić in Clementinum, Prague, Czech Republic (unveiled in a ceremony on September 23, 2011)

This one is for all the brainy, science types out there, which you can tell by the title.  An interesting fact, but not my thing at all. And probably just scientist types for the most part will google his name and find this post.  Just way too much math involved for my liking.  Although now maybe the name of pioneer meteorologist, seismologist, and geophysicist Andrija Mohorovičić will be a little more familiar.   Anyway, a new satellite high-resolution map of the the earths boundary between the core and mantle just came out, known as the "Mohorovičić discontinuity".

The  150th anniversary of his birth commemorated on a 1000 Kuna gold coin.

As a young student.

It's named after the Croatian scientist who first identified it back in 1909.   A science that is an earth centered version of the space proram.  Insted of exploring unknown deep space, this science explores unknown deep earth.   He also later discovered a technique for locating earthquake epicentres and calculated the travel time of seismic waves. He was an early advocate of earthquake-resistant construction.  I'm not going to get into all the details, you can read the articles below for that, but it's kind of cool finding out that there's another crater on the moon named after another Croatian scientistschools, an asteroid, and even a ship that is part of the Croatian Coast Guard..

 BŠ-73 Andrija Mohorovičić. Image:

I came across HERE the courses he took back in university, and he was definitely one of those brainy types who fit in well using various mathematical formulas.   (I met a few science type chicks in Zagreb last time at Klub Purgeraj, so rest assured, they're not all old men)  Just an interesting Croatia related piece for the brainy science types out there.  Perhaps dry and boring to many, including me, but to the science world, and how his discovery relates in relation to today's world, it's was pretty important stuff.  Like all previous scientific discoveries affect the next ones, and the world today.  ( Like the people who discovered  that farts are flamable, I was at some hockey get togethers in my teens, and some sporto-jock parties in high school, football team related, where that discovery was celebrated like you wouldn't believe. Very important)  For those who are inclined to complicated science and long involved mathematical equation's or who are science buffs,  I added a video to explain a bit more about what exactly his discovery was.  More information at the links below....

 Goce flies lower than any other scientific satellite (photo credit: AOES Medialab)

Related links:

Goce gravity data traces Moho boundary 


Scientists have mapped the boundary globally between the Earth's crust and its mantle - the so-called Moho boundary - in unprecedented detail. They used gravity measurements from the European Space Agency's Goce satellite to model its location. The famous "discontinuity" lies some 10-70km below the surface and marks a sharp change in rock properties.  It was first identified by the Croatian geophysicist Andrija Mohorovicic in 1909.

He determined the boundary's existence from the distinct behaviour of seismic waves produced by shallow earthquakes.  Goce can be used to sense the Moho's depth because it is able to detect subtle variations in the Earth's gravitational field.  These differences result from the uneven distribution of mass inside the planet - a signal that also reflects the major shift in rock density that occurs at the boundary.

"At the Moho, there is a discontinuity between the compositions of rock - there are rocks of different density," explained Dr Daniele Sampietro from the Politecnico di Milano, Italy. "The crust has a smaller density while the mantle has a bigger density. And since the change in density means there will be a change in mass, I can use Goce to observe the Moho."

The new global map shows clearly that the boundary's depth is greatest under the big mountains, and at its shallowest under the oceans.  Today's scientists recognise the interface to be where familiar surface rocks of predominantly basaltic or granitic composition give way to peridotites. These rocks comprise magnesium-rich, silicon-poor minerals such as olivine and pyroxene and are rarely seen at the surface.

Getting a clearer picture of where the discontinuity lies will aid the study of plate tectonics, the mechanism that explains how the Earth's rigid outer shell moves and is recycled into the planet's interior.  The information is likely also to be useful to those seeking new oil and gas resources, by making it easier to discern deep geological structures.

There are places, such as in Cornwall in southwest England, where chunks of ancient Moho have been thrust to the surface, but it remains a key quest for scientists to drill down and retrieve pristine samples of rock from either side of the discontinuity.  Such a venture is more likely to happen under the oceans because that is where the crust is thinnest.

An attempt was started in the early 1960s (Project Mohole) but was soon abandoned because of the high cost of meeting the engineering challenge.  The Gravity Field and Steady-State Ocean Circulation Explorer (Goce) was launched in 2009. It flies pole to pole at an altitude of just 255km - the lowest orbit of any research satellite in operation today.

The spacecraft carries three pairs of precision-built platinum blocks inside its gradiometer instrument that sense accelerations which are as small as one part in 10,000,000,000,000 of the gravity experienced on Earth.  This allows it to map the almost imperceptible differences in the pull exerted by the mass of the planet from one place to the next - from the great mountain ranges to the deepest ocean trenches.

Footage from 2010 of the unveiling of a plaque commemorating the 100th anniversary of the now widely known "Mohorovicic discontinuity".

Andrija Mohorovičić (1857-1936)—On the occasion of the 150th anniversary of his birth.

Andrija reportedly liked to have a few stiff shots of brandy and rakija with his cigarettes and cigars.


Andrija Mohorovičić, a world-renowned seismologist and the greatest Croatian scientist of all time, was born 150 years ago on 23 January 1857 in Volosko near Rijeka, Croatia. Although his name is mostly associated with the discovery of the crust-mantle boundary, his other achievements in seismology, as well as those in other geophysical disciplines, certainly deserve to be remembered.

Mohorovičić enrolled in Prague University to study mathematics and physics in 1875. The very solid foundations in science that he obtained from professors such as Ernst Mach and Heinrich Durège are clearly reflected in his later work and scientific attitude. An overview of his days in Prague is given by Orlić (1998). After graduation he taught at high schools in Zagreb and Osijek and at the Nautical School in Bakar. In 1892 he became the director of the Meteorological Observatory in Zagreb. The following year Mohorovičić obtained the doctorate of philosophy at Zagreb University, where he was later elected an adjunct associate university professor to teach courses on geophysics and astronomy. He became a corresponding member of the Yugoslav Academy of Science and Arts in 1893 and a full member in 1898. Mohorovičić retired in 1922. An excellent and thorough account of his life and scientific accomplishments was published in a monograph by Skoko and Mokrović (1982, 1998) in Croatian and English.

At the beginning of his career Mohorovičić focused on meteorology. His scientific interests lay in the explanation of various meteorological phenomena—atmospheric dynamics and observations of rare events (e.g., a tornado near Novska or the whirlwind near Čazma). He also studied the climate of Zagreb and the decay of temperature with altitude. Looking to learn more about the atmospheric circulation but lacking proper instruments, he built his own nephoscope, a camera obscura-like instrument for observation of clouds. These observations formed the basis for his dissertation. As only recently rediscovered (Grubisić and Orlić 2007), Mohorovičić was the first person to describe atmospheric rotors with a horizontal axis, which he observed during bora-wind episodes in the northern Adriatic. The paper about it appeared in 1889 in one of the leading meteorological journals of the time and was immediately translated into English. It somehow disappeared from reference lists in the 1930s.

The following quotation, from 1901, perhaps best illustrates the clarity of Mohorovičić's vision:

" The ultimate goal of a meteorologist is to set up differential equations of the movements of the air and to obtain, as their integral, the general atmospheric circulation, and as particular integrals the cyclones, anticyclones, tornados, and thunderstorms. "

A brief to the point simplification of his discovery. (Yes, the narrator butchers his name btw, it's more like And-reeyah Moho-rov-chich)

A perfect description of today's weather forecast, at the very beginning of the 20th century it was beyond even science fiction. Mohorovičić is also recognized for the high standards he set for professional meteorology and for the unification of the meteorological service in Croatia. He was the first in Croatia to publish weather forecasts in daily papers.

About the turn of the century Mohorovičić's scientific interest turned almost exclusively to seismology, although he continued to spend a tremendous amount of time on routine meteorological observatory duties. It is indeed remarkable for a scientist who decided to turn his career upside-down in his mid-forties by starting research from scratch in a new, almost nonexistent field in his country, to subsequently achieve such an international reputation. The reason for this dramatic change is not known—one can only speculate that intense seismic activity around the Croatian capital in the late 19th century ignited the spark in his curious mind. The formal background was also set, as an Earthquake Committee of the Yugoslav Academy was established in 1880 when Zagreb was devastated by a large earthquake, and Mohorovičić later became actively involved. He founded the Zagreb seismological station in 1906, when he installed the Vicentini-Konkoly seismograph in the basement of the Meteorological Observatory (and on seismogram number 9 he recorded the great San Francisco earthquake!). Soon he realized that better instruments were needed, and he purchased Wiechert horizontal seismographs, which became operational in 1908 and 1909. He wrote at the time, “with this we are on the level with all the better observatories in Central Europe.”

The meticulous analyses of recordings of the Kupa Valley earthquake of 8 October 1909 (Mohorovičić 1910a, b, c) made by these instruments, together with seismograms collected from all over Europe, enabled him to prove the existence of the crust-mantle boundary, which later became known as the Mohorovičić discontinuity, popularly known as the Moho. This unveiling of one of the big secrets of the Earth's interior places him among the founding fathers of modern seismology. It was in line with how he saw the essence of this young scientific discipline:

" The goal of seismology is to study the interior of the Earth, and to continue where the geologist stops; it has in modern seismographs a sort of binoculars that enables us to look into the largest of depths. "

This discovery, recognized as one of the milestones of science in the beginning of the 20th century, is also the most important scientific contribution ever published in a Croatian journal. The paper itself was unusual, at least by today's standards—published bilingually (Croatian and German in the same volume) in the Observatory bulletin, it had a title that was not informative at all, was rather lengthy (56 pages), and was written in a narrative form stating all of Mohorovičić's dilemmas, observations, ideas, and trials. The number of topics covered and the number of important contributions in the paper were remarkable. In this one paper one finds: the macroseismic case study of the Kupa Valley earthquake of 1909; the proof of the existence of the discontinuity together with a complete theory of propagation of seismic waves in the new Earth model; inverted model parameters (P- and S-velocities, interface depth, exponential laws of velocity increase with depth within the crust and in the upper mantle—Mohorovičić's law); the first empirical and theoretical hodochrones for the phases he introduced at local and regional distances (Pg, Sg, Pn, Sn, together with a large number of crustal reflections, including converted phases!); instructions on how to estimate epicentral distance based on onset times of a multitude of phases on the seismograms; new procedures for determination of focal depth; prediction about what the seismograms of (then unknown) deep earthquakes should look like; a suggestion that the “maximum phase” (Lg or Airy phase) is closely related to channeled post-critically reflected S waves within the crust even for distant events. His train of thought closely follows Feynman's (1967) “recipe” for the creation of a new physical law—guess it, compute consequences, compare them to nature and observations, if they agree it is right, if they disagree it is wrong (paraphrased). This trial-and-error approach is even today often the method of choice in solving inverse problems, one of the first of which in seismology was solved by Mohorovičić in 1910.

There are also other, less-known achievements of his, including an elegant method of location of epicenters (Mohorovičić's epicentrals, 1915-1918), a method to determine total friction in mechanical seismographs (1917, 1918, 1924), a novel seismograph design (1917, 1918, unfortunately never realized), a number of improved travel-time curves (1914a, b, c), etc. Mohorovičić was also among the first to recognize the importance of the seismic-resistant design of buildings. In a series of lectures for the Croatian Society of Engineers and Architects, as early as 1909 (published in 1911) he attempts to “explain how the Earth trembles, and how these tremors affect buildings, and draw attention to some principles that both architects and building contractors should follow.” Furthermore: “In order to study earthquake effects on buildings, we must first accurately represent the shaking of soil beneath the building, as well as the forces this shaking exerts, and then we must study how these forces affect the building as a whole and its individual parts.” He went on to analyze the effects of building resonance and computed accelerations for various ratios of the period of dominant shaking and the building eigen-period. Quite ahead of his time, he set some of the basic principles of earthquake-resistant design and warned against erecting heavy buildings on soft ground and steep slopes and suggested firm joints between the basic building skeleton, the beams, and the walls, etc. He was also the first one to statistically compute expected exposure of buildings in Zagreb to earthquakes, and he tried to persuade entrepreneurs “to consider the earthquake hazard and spend more, in order to make buildings more resistant and safe.” Out of six basic principles of conceptual design for aseismic building construction as outlined in the current Eurocode-8, Mohorovičić advocated five of them already at the beginning of the 20th century!

Andrija Mohorovičić was a very careful, thorough, and diligent scientist who enjoyed the search for explanations of observations in theory, but never favored theory over observations. A true erudite, he spoke—besides his mother tongue—English, German, Italian, French, and Czech (in addition to Latin and Greek). He published about 40 papers, of which he was always the only author. This speaks not of his vanity but rather of hard conditions he had to work in, resulting in a persistent shortage of coworkers.

His thoughts and ideas were truly visionary, often decades before his time (harvesting wind energy, hail suppression, models of the Earth and of the atmosphere, deep earthquakes, earthquake-resistant design, etc.). In 1970 one of the craters on the dark side of the moon was named after him, as was the asteroid No. 8422 in 1996. The crust-mantle boundary on the moon as well as on Mars is also known as the Mohorovičić discontinuity.

Andrija Mohorovičić is one of only very few Croatian scientists of an international reputation who spent his whole career in his homeland. He is recognized as the founder of the Zagreb seismological school, the Croatian Seismological and Meteorological Surveys, and the public time service. Owing to the tradition he initiated, the University of Zagreb is among the few in the world awarding a degree in seismology at the under-graduate as well as the graduate level.

Courses that Andrija Mohorovičić attended during his studies (I find it cool and interesting how he took the Slavic Mythology, Art History, Literaure and History of Slavic languages courses along with all his other science/math courses, which is more up my alley.)

Throughout the year 2007, the Department of Geophysics of the Faculty of Science in Zagreb organized a series of events to mark the sesquicentennial of Mohorovičić's birth. Among the commemorations and many lectures about his life and scientific achievements three events stand out: the unveiling of the newly erected bust in front of the house in which he was born and lived during his childhood in Volosko, the painting contest for schoolchildren with geophysics and his achievements as the motif, and the issuing of a postage stamp in his honor. The stamp, reproduced here on the cover of this issue of SRL, was promoted in Zagreb on 23 April 2007 and subsequently in Rijeka four days later. To have two promotions is quite exceptional—the second one was organized because of the high interest from his native region. Both events were accompanied by excellent philatelic exhibitions dedicated to meteorology and geophysics (by D. Poje, M. Vučetić, E. Hernitz, and T. Gregl in Zagreb) and to seismology and earthquakes (in Rijeka, presented by P. Suhadolc from Trieste University).

On the occasion of the centenary of the Zagreb seismological station, the Andrija Mohorovičić Memorial Rooms were opened in the premises of the Department of Geophysics in Zagreb. There we display Mohorovičić's original instruments—Wiechert seismographs, observatory clocks, chronometers, astronomical instruments, microbarograph and barometers—all restored and in prefect condition; and his furniture, documents, correspondence, papers, manuscripts (including complete derivations leading to the discovery of the crust-mantle boundary), photographs, posters, etc.

Many people at the time thought that perhaps Mohorovcic was well on his way to pinpointing the exact location of Hell.  Some experts with the same views as Pat Robertson (below) thought that if the proposed deep well holes were accomplished, the result may be millions of yellow toothed and stinky fingered demons gushing out with the oil and gas to torment mankind.  Hiding in barrels of oil they would then appear to force people to sing and speak in nonsensical jibber-jabber tongues, wear pleated plants and penny loafers daily and get bi-weekly haircuts.

Some people, like this Abraham Lincoln look-a-like preacher guy below, thought that Andrija Mohorovičić had proved the existence of the hiding places of dinosaurs under the earth, (along with billions of dead things all over the earth layed down by water, billions of them in rock layers, billions of them of sharped teeth fossils all over the earth before the chicken) and that dinosaurs would soon once again roam the earth even to your local park.

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