Flashback Post LXIX

Yesterday's Magnitude 8.8 earthquake, off the coast of eastern Russia's Kamchatka Peninsula, was the 6th most powerful quake ever recorded.  Geologically speaking, it occurred along a subduction zone, triggering a tsunami warning across the Pacific Ocean.  A post from April of 2009 explained this phenomenon.

See: Tsunamis and Subduction Zones 

The Myanmar Earthquake

The tragic, 7.7 magnitude earthquake in Myanmar this week occurred along fault lines between the Indian and Eurasian Plates.  The former continues to push NNE into the latter, forcing up the Himalayas and producing frequent earthquakes in that area.  Adding to tectonic pressure within that region is the subduction of the Indo-Australian Plate beneath the southeast portion of the Eurasian Plate.

While these powerful earthquakes seem to have a predilection for impoverished countries, where the houses and buildings do not meet modern codes, this is a false narrative.  That assumption is derived from the fact that much of the planet remains relatively "underdeveloped."  Of course, our brief time on Earth also fosters that conclusion.

Here in the U.S., most quakes have been relatively mild over the past Century but major, destructive events lie ahead, especially along the West Coast (an Active Margin).  We can contribute to relief efforts and, perhaps, improve our quake prediction accuracy but we will never control tectonic activity. 

Flashback Post XLVII

Yesterday's powerful earthquake on the west coast of Japan was a consequence of that country's complex tectonic structure, a subject discussed in a post back in September of 2008.

See: Earthquake Central

Flashback Post XXXVII

This week's tragic earthquake in Turkey and Syria brought to mind a post that I wrote in October of 2011. Understanding the reason for the catastrophe does not diminish the importance of a swift International response.

See: Turkey & Earthquakes 

Flashback Post XXXIII

The current tragic flooding in Pakistan even exceeds the catastrophe that I documented in a post twelve years ago.  Unfortunately, global warming will significantly increase the incidence of these events.

See: Pakistan's Catastrophic Flooding 

The Alborz Mountains

While watching Tehran, a miniseries on Apple TV (which I recommend), one repeatedly sees the majestic mountain wall just north of the city.  These are the Alborz Mountains and the snowy massif near Tehran is Tochal, elevation 13,005 feet.

Wrapped along the southwest and southern coasts of the Caspian Sea, the Alborz Range crumpled up during the mid-late Tertiary Period as the Tethys Sea closed and the Arabian Plate collided with the Eurasian Plate, a process that continues today.  In concert with that uplift, volcanism occurred in some areas and Mt. Damavand, northeast of Tehran, is a volcanic cone that rises to 18,406 feet, the highest point in the Middle East.

Though less famous than the Alps and the Himalayas, the geologic and natural history of the Alborz Mountains is very similar; indeed, they are one of multiple smaller ranges that connect the Alps and Himalayas, creating a mountain corridor from France to Southeast Asia.

Magellan's Mixed Legacy

Ferdinand Magellan was certainly a courageous individual and an exceptional navigator, having crossed the Atlantic, maneuvered through a dangerous, unmapped strait and rallied his crew as they spent months on an unknown ocean (the Pacific), dying off from malnutrition and scurvy.  Then again, he took on slaves, ordered the slaughter of many native villagers and left two mutineers on a small, uninhabited island.

And just as his goal was about to be realized, having received a warm welcome from natives in the Philippines, he attacks a king and his tribe who refused to convert to Catholicism; Magellan was killed in that battle and his remains were never recovered.  In more stark terms, Magellan survived nineteen months at sea, often under trying conditions and in uncharted waters, to die on a beach in the Philippines during a battle of his own making.

Of course, Magellan's journey began not long after the Spanish Inquisition, when religious fervor was at a peak.  But here was a man who undertook a treacherous circumnavigation of our planet based on the leading scientific assessments of his day only to succumb to religious mysticism.  On both counts he taught humanity a great deal.

See the previous three posts for details, all taken from Over the Edge of the World, by Laurence Bergreen 

Crossing the Great Ocean

It took Magellan's crew a full month to negotiate the straight that would come to bear his name.  Strong currents, fog, a tortuous course, dangerous rocky outcrops and shifting gales slowed progress and a mutiny on the San Antonio, the main supply ship, cut the fleet to three boats by the time they entered the Pacific in late November, 1520.

Having no concept of the great distance that still lie ahead, Magellan sailed northward, paralleling the coast of South America as far as present-day Santiago, Chile.  Then angling to the WNW, his ships caught the trade winds and enjoyed pleasant weather for the next three months.  Unfortunately, since maps of the Pacific had not yet been created by Europeans, the fleet could not "island hop" to restore supplies; malnutrition and scurvy took a significant toll on the crew before they finally reached Guam in early March, 1521.  There they encountered friendly natives whom they managed to mistreat and kill despite receiving life-saving food and water.

By mid March, the fleet reached the Philippines, having crossed the Pacific Ocean in three and a half months.  Today, we know that their goal of reaching the Spice Islands (Indonesia) was nearly realized but, in 1521, with no maps of Southeast Asia available, Magellan and his crew were as lost as they were at the Strait.

Note:  As mentioned in the last two posts, these brief summaries are taken from Over the Edge of the World, by Laurence Bergreen.  Interested readers are encouraged to obtain that highly-detailed but easily read account of Magellan's Journey.

See also: Polynesian Migration  for perspective on pre-European colonization of the Western Pacific.

Sailing with Magellan

Attending a used book sale last week, my wife bought Over the Edge of the World, by Laurence Bergreen, which documents "Magellan's Terrifying Circumnavigation of the Globe."  She thought I might enjoy the book and, as usual, she was right.  Ironically, Magellan, his 260 man crew and their five ships set off from Seville, Spain, 500 years ago this month!

Portuguese by birth, Magellan came of age during the Golden Age of Portuguese navigation, when Vasco de Gama and other mariners established trade routes to the Spice Islands (Indonesia) by sailing along the southern coasts of Africa and Asia.  Convinced that he could reach that same destination by heading west (but denied funding by Portugal), Magellan turned to the King of Spain to sponsor his voyage, promising to return within two years with untold riches from the Spice Islands.

Three years later, a handful of the original crew members and only one ship (the Victoria) limped back to the Spanish Coast, devoid of riches but having proved, for the first time, that our home planet is indeed a globe.  Highlights of Magellan's expedition (all from Bergreen's account), will be offered in coming posts.  Having read the first few chapters to date, I highly recommend the book.

Mystery Tsunami in Indonesia

Yesterday, following two earthquakes (the second a magnitude 7.5 quake) and a series of aftershocks off the west coast of Sulawesi Island, a tsunami struck Palu, at the end of a long, narrow bay.  Both the Island and the adjacent Makasser Strait lie squarely on a southern extension of the Eurasian Plate, which encompasses all of Indonesia.

Destructive tsunami's are generally triggered by Subduction Earthquakes, where one tectonic plate dips beneath another; such a subduction zone stretches along the outer border of Indonesia, where the Australian and Philippine Plates are subducting beneath the Eurasian Plate.  Yesterday's series of quakes and aftershocks are thought to have developed along a transverse fault, where two microplates (of the Eurasian Plate) are scraping past one another; such faults do not generally produce vertical lift of the overlying sea, the tectonic process that usually generates tsunamis.

Geologists suspect that some vertical movement of one of the microplates may have occurred and that the topography of the narrow bay likely amplified the wave that was produced.  Regardless of the geologic explanation, the tsunami struck Palu and killed at least 384 residents and visitors.

Update:  As of 10-3-18, more than 1400 bodies have been recovered and the death toll is expected to rise.  

Relentless Evolution

We modern humans are the products of 3.6 billion years of evolution, governed by genetic mutations, genetic recombination (through sexual reproduction) and the overriding process of natural selection.  Even among the global human population, differences have developed as tribes have adapted to their environment (e.g. darker skin in those native to the Tropics and more adipose tissue in those native to the Arctic region).

Today I came across an article in the New York Times which reports on a study from the journal Cell.  It describes an anatomic alteration present in the Balau people of Southeast Asia, a coastal culture that has long sustained itself by deep diving to spear fish and to collect mollusks from the sea bed.  Known for their ability to remain underwater for prolonged periods of time, members of this tribe were found to have enlarged spleens (an organ that is also enlarged in other diving mammals such as seals and which plays an important role in the diving reflex observed in all mammals).  Of particular interest is the fact that all Balauns have enlarged spleens, even those who do not engage in diving; this suggests that it is an inherited trait, emplaced by natural selection.  Researchers suspect that this diving culture developed as sea levels rose at the end of the Pleistocene, forcing islanders to rely on marine creatures for their sustenance.

Many humans, especially those inclined toward mysticism, believe that we humans are the pinnacle of creation, the Chosen Species.  In fact, we have evolved from other primates and continue to evolve.  Hundreds of thousands of years from now, if we have not destroyed our planet, we may well have evolved into a new species.

The Korean Peninsula

In light of the ongoing Olympics, I thought I might take a look at the geography of the Korean Peninsula.  Extending southward from northeastern China and extreme southeastern Russia, the Korean Peninsula separates the Sea of Japan, to its east, from the Yellow Sea, to its west.  More than 65% of the Peninsula is covered by mountainous terrain, primarily across its northern and eastern regions.  Most of the ranges are composed of Precambrian igneous and metamorphic rock though some areas of volcanism exist as well.  Paektusan, just over 9000 feet, is the highest summit on the Peninsula, rising along the border of China and North Korea; it is known for it large caldera (created by a massive eruption in 946 AD) which holds Heaven's Lake.

Three major rivers drain most of the Korean Peninsula: the Nakdong flows southward through its southeastern region, the Han River flows westward through the central portion of the Peninsula (passing through Seoul) and the Taedong River flows southwestward through the northern Peninsula, passing through Pyongyang.  More than 3500 islands and islets rise off the western and southern coasts of the Peninsula, including Jeju, a large volcanic island in the Korean Strait (south of the Peninsula) which was formed by Hallasan (6398 feet), a large shield volcano that is the highest peak in South Korea.

While the Korean Peninsula extends across the same latitudes as Japan, it does not enjoy the warming effects of the Japan Current and its continental climate is considerably colder.  PyeongChang County, which is hosting the 2018 Winter Olympics, is about 78 miles east of Seoul.

Eruption of Mount Agung

Mount Agung, 9944 feet, is in western Bali.  One of 78 active volcanoes in Indonesia, its last major eruption occurred in 1963 but another is expected within the next few weeks.  Earthquakes developed on and near the volcano back in September and the release of smoke and ash has been intermittent throughout October and November.

The volcanic islands along the western and southern edge of Indonesia have formed as the Indo-Australian Plate has been subducting beneath a southeastern extension of the Eurasian Plate.  As it is forced downward, toward the Earth's mantle, the leading edge of the subducting plate melts and plumes of magma push up through the crust of the overriding plate.  Initially producing a volcanic island arc, the ongoing subduction and volcanism has culminated in the large islands that we observe today (Sumatra, Java, Bali and others to their east).

Another major eruption of Mount Agung will likely produce widespread devastation but will not come close to the effects of Mount Toba's eruption, on Sumatra.  That supervolcanic eruption, which occurred 74,000 years ago, temporarily cooled the Earth's climate and had a major impact on the human population of our planet; indeed, a significant percentage of early humans had left Africa and colonized the southern rim of Asia by that time (see The Toba Winter).

Iran-Iraq Earthquake

A magnitude 7.3 earthquake struck the Iran-Iraq border region yesterday; the initial death toll is over 450 individuals and is almost sure to rise.  The quake occurred in an active tectonic zone where the Arabian Plate is colliding with the Eurasian Plate.

About 40 million years ago, the Red Sea began to open, rifting the Arabian Plate from the African Plate; this rift continues southward as the East African Rift that will eventually split the Continent.  Twenty million years later, during the Miocene Period, the Gulf of Aden began to open as well and the combined forces of these active rifts zones are pushing the Arabian Plate to the NNE; its collision with the Eurasian Plate has been crumpling up the mountain ranges of Iran and Turkey, a process that continues today.

While the tectonic drift of continents is too slow for humans to observe during our brief life spans, the sudden release of pressure along fault lines, resulting in earthquakes, attests to the massive forces involved in this process.  Having sculpted the surface of our planet long before our species evolved, we must now live with the consequences of plate tectonics (See also The Eurasian Mountain Arc).

The Kyushu Earthquake

The islands of Japan sit at the convergence of four major tectonic plates: the Eurasian, North American, Pacific and Philippine Plates.  Throughout most of their history, the Pacific Plate was moving northwestward, bringing in terranes and producing volcanic island arcs as it subducted beneath the North American and Eurasian Plates.

About 45 million years ago, the movement of the Pacific Plate shifted to a westward direction (as evidenced by the angle change of the Hawaiian Ridge), creating the Philippine Plate as the Pacific Plate began to subduct along the Izu Bonin Trench.  Surrounded by subduction trenches, the Philippine Plate now subducts beneath the southern half of Japan (which lies on the Eurasian Plate), including Kyushu Island, fueling volcanic activity and triggering earthquakes.

This week's earthquake on Kyushu Island, which killed at least 9 and injured hundreds, was a magnitude 6.2 quake, centered beneath the Island just west of Kumamoto.  While subduction forces initiated the earthquake, it occurred due to slippage along a fault that bisects the Island, separating older and younger terranes.  Shifting pressure along this and associated faults led to numerous aftershocks that may continue for weeks.  Since the earthquake developed on land (not at the subduction trench itself), there was no risk of a tsunami; on the other hand, the quake could have triggered a volcanic eruption, a complication that, to date, has fortunately not occurred.

Addendum:  A second, far more powerful (magnitude 7.0) earthquake has struck near Kumamoto.  Initial reports indicate widespread damage, including landslides, and at least 26 deaths (in addition to those killed by the quake earlier this week).

Earthquake in Nepal

Unlike many earthquakes, which develop along hidden faults beneath oceans or featureless plains, today's magnitude 7.8 quake in Nepal is easy to understand, even for the novice geologist.  The Indian Subcontinent, which broke from Antarctica and Australia some 80 million years ago, has been plowing into southern Asia for the last 50 million years, crumpling up the Himalayas, the highest range of mountains on Earth.

The tectonic force responsible for this ongoing collision is sea floor spreading in the western Indian Ocean, triggered by mantle currents beneath the ocean crust.  Inching to the NNE, India has fused with Asia and the intervening ocean crust is now incorporated within the mountain massif; indeed, Mt. Everest, the highest point on our planet, is capped with marine limestone.

Today's earthquake in Nepal, coupled with new eruptions of the Calbuco Volcano in southern Chile, remind us that the surface of our planet remains in flux, its tectonic plates rifting, colliding, subducting and scraping past one another.  Driven by heat within Earth's core, this geologic process has continued for almost 4.6 billion years; we humans, having evolved less than 150,000 years ago, have come to understand plate tectonics but remain susceptible to its destructive force.

The Dead Sea Transform

The Dead Sea Transform marks the western edge of the Arabian Plate, extending from the East Anatolian Fault (in southeastern Turkey) to the northern portion of the Red Sea.  Much of the Transform is occupied by the Jordan River Valley; 220 miles long, the Jordan River rises on the slopes of Mt. Hermon (along the border of Syria and Lebanon) and flows southward to the Dead Sea, passing through the Sea of Galilee en route.  The southern end of the Dead Sea Transform is occupied by the Gulf of Aqaba, the northeastern arm of the Red Sea (and the eastern edge of the Sinai Peninsula).

The northward movement of the Arabian Plate (which continues today) began in concert with the opening of the Red Sea (part of the East African Rift), a tectonic process that dates back to the Miocene (some 10-15 million years ago).  Whether the Dead Sea Transform is merely a transform fault between the African and Arabian Plates (comparable to the San Andreas Fault between the North American and Pacific Plates) or whether it, like the Red Sea, is a true rift valley is a matter of debate among geologists.

The Dead Sea, 1300 feet below sea level, is the lowest point on Earth's Continents.  Whether the Jordan Valley is a spreading rift valley or not, one suspects that it will one day be flooded by the sea, continuous with the Gulf of Aqaba and the Red Sea.

The Java Sea

Recently in the news due to the crash of Air Asia Flight 8501, the Java Sea is the southern section of a vast shallow sea that extends southward from Thailand, Cambodia and Vietnam to the southern islands of Indonesia.  Averaging just 150 feet in depth, the Java Sea was an inland plain during the Pleistocene Ice Age.

Indeed, the archipelagos of Malaysia, Indonesia and the Philippines occupy a broad peninsula of the Eurasian Plate, extending southward from what is now the Southeast Asia mainland.  Subduction volcanoes rim the peninsula, where the edges of the Australian, Pacific and Philippine Plates are being shoved beneath the Eurasian Plate.  As the climate began to warm near the end of the Pleistocene, some 15,000 years ago, continental and cordilleran glaciers began to melt and sea levels rose; of course, this process continues today, intensified by our use of fossil fuels.  Moving up coastal river valleys, the ocean waters spilled across lowlands of the Eurasian Peninsula, producing archipelagos of high ground.

Transient shallow seas, such as the Java Sea, have left sedimentary strata across the Continents; marine limestones, dolomites, shales and siltstones cover most of the ancient Precambrian basement rock, as do sandstones deposited as beaches along the shallow seas.  Seemingly a permanent feature of Earth's landscape from the perspective of our brief human life span, the Java Sea will expand and contract as sea levels rise and fall; its sediments, now scoured to retrieve aircraft debris and human remains, may, in the distant future, be uplifted and sculpted into mesas, plateaus or mountain ranges.

Tragedy on Mount Ontake

Japan sits at the intersection of four major tectonic plates, making that country especially prone to earthquakes, tsunamis and volcanic activity.  Indeed, subduction volcanism produced the Japanese archipelago as the Philippine and Pacific Plates have been forced beneath the Eurasia and North American Plates, respectively.

Two days ago, just before noon, Mount Ontake erupted, pelting the summit with rocks and up to two feet of volcanic ash.  A popular site for hiking, especially during the autumn color display, this 10,120 foot peak (125 miles west of Tokyo) was crowded with visitors at the time of the eruption; at least 36 hikers were killed and many more were injured.  Unfortunately, recent quakes in the area were not thought to portend an imminent eruption and access was not restricted; now, further eruptions are anticipated.

Direct evidence that tectonic activity continues to mold our planet, this tragedy is also a reminder that volcanologists cannot yet accurately predict when eruptions will occur.  Mount Ontake, long dormant and once thought to be extinct, had its only prior documented eruption in 1979 (though a minor one followed in 1991 and the release of steam was observed in 2007).  Individuals who live in subduction zones (Indonesia, the Aleutians, the Cascades, the Andes and others), those who reside near hotspots (Hawaii, the Yellowstone region, northern Arizona) and those who inhabit rift zones (Iceland, East Africa, the Rio Grande Valley) cannot become complacent, even after long periods of regional volcanic inactivity.  After all, our human lifespans are but an instant in the geologic and tectonic history of Planet Earth.

Arctic Sinkholes

Over the past few decades, climatologists have documented a gradual reduction in both the thickness and the expanse of Arctic sea ice, a result of global warming that has been documented across the planet.  This summer, as was reported on PBS last evening, new and unexpected findings in the Arctic appear to offer additional evidence of Earth's ongoing climate change.

Several large sinkholes have been discovered on the Arctic tundra of northern Siberia; edged by loose soil, there was initial suspicion that they might represent small impact craters.  Others suggested that the holes may have resulted from the eruption of subterranean pockets of methane.  At this point, however, most of the investigators have concluded that they are true sinkholes, having developed due to melting of deeper layers within the permafrost; this process has created water channels, undermining the surface of the tundra.

While the surface of the Arctic tundra has long thawed during the summer months, the deeper permafrost has remained frozen since the last glacial period of the Pleistocene.  Apparently, the global warming that began at the peak of that glaciation (some 20,000 years ago) and has accelerated since the onset of the industrial revolution, has now reached a point where the permafrost is threatened.  As more sinkholes develop, climatologists also suspect that significant amounts of carbon dioxide and methane might be released from the Arctic subsoil, a potential massive source of the greenhouse gasses that fuel global warming.