Earthquakes That Changed the Earth: How Catastrophic Quakes Reshape the Surface

Geological processes that reshape the face of the Earth unfold so slowly that noticeable changes — the height of mountains, the width of a river valley, the formation of a cave and the like — require immense spans of time, often measured in millions of years.

Yet alongside these gradual transformations there are instantaneous ones that alter everything around us beyond recognition, right before a person's eyes. These geological changes to the Earth's surface take place during earthquakes. So which earthquakes have transformed the face of the Earth? This page surveys the most catastrophic seismic events recorded in history, from Lisbon and Messina to Tokyo and Tōhoku, the geological scars they left, and the related phenomenon of seaquakes. Which earthquakes changed the face of the Earth? Geological changes to the Earth's surface during an earthquake

What are catastrophic earthquakes and how do they reshape the land?

Catastrophic earthquakes can rework the surface of the Earth within minutes, opening fissures kilometres long, raising or lowering coastlines, triggering massive landslides and damming entire rivers. A few well-documented examples show the scale of these geological changes:

• The powerful Assam earthquake of 1897 (in the north-eastern province of India) covered an enormous area, with the most severe destruction spread over a region roughly the size of the Caucasus. Gaping fissures up to 22 kilometres long opened up, with vertical displacements of as much as 11 metres along them. Grand landslides swept down the mountains, carrying the forests that clothed their slopes with them, and the debris dams created huge ponds on the rivers.
• Even more striking geological changes occurred during the earthquake in southern Alaska in 1899. Here new islands appeared, the coastline shifted, the shore was lifted by up to 16 metres vertically, and numerous faults and fissures formed.
• The mighty Usoy landslide, triggered by the Pamir earthquake of 1911, buried the deep gorge of the Bartang River near the village of Usoy. Behind this enormous natural dam, Lake Sarez formed, named after the village of Sarez that was entombed by the slide. Today the lake is more than 70 kilometres long and reaches depths of up to 500 metres in places.

Why is an earthquake such a terrifying natural phenomenon?

No other formidable natural event affects a person as profoundly as an earthquake. Under a clear sky, thunder-like subterranean rumblings suddenly resound — an ominous roar, the whistle of wind, the shriek of a flying shell — and the very firmament of the Earth, which our minds associate with something immovable, solid and steadfast, is set in motion. The aftermath of earthquakes

Waves run across the ground as if over water, sharp jolts and powerful underground shocks are felt, trees sway like ears of corn in the wind, ominous cracks appear in the roads, buildings collapse, and tremendous landslides occur in the mountains.

Among the disasters humanity has experienced and recorded in its legends and documents, earthquakes rank first both in the number of victims and in the scale of material loss. Earthquakes are often accompanied by the collapse and subsidence of substantial areas of land. Sinkholes are rounded in shape and fill with water

Entire cities have vanished into vast sinkholes:

• In Chile in 1868 the town of Catacachi "sank into the ground."
• In 1869 the same fate befell the town of Onlag in Asia Minor. Lakes formed on the sites of both towns.
• The Kudara earthquake, one of the largest in the Baikal region, caused the subsidence of an enormous area (12 January 1862) to the north-east of the Selenga River delta. Part of the Tsagan Steppe (about 100 square kilometres in area), together with all the dwellings and herds upon it, sank beneath the waters of Lake Baikal. This bay, up to 8 metres deep, is still called the "Proval" (the Subsidence).

How do earthquakes create cracks in the ground?

The appearance of cracks in the ground, into which people and animals fall, instils terror in the human mind. The edges of the fissures shift together and the dead vanish forever, though subsequent tremors sometimes cast their bodies back out again. The fissures can be so wide (up to 10–15 metres) and deep (up to 10 metres) that entire buildings, vehicles and people fall into them. A crack in the ground after an earthquake

The opposite phenomenon has also been observed, when powerful underground shocks threw houses out of the earth together with their foundations, and paving stones flew up like cannonballs. When fissures cut through water-bearing strata or through quicksand made of water-saturated sands, streams of water and mud are thrown out of the Earth's belly, flooding the surrounding area.

The same happens when a city's water-supply and sewage networks are ruptured. When the urban gas network is severed, gas bursts from the cracks and ignites in the air in vast pillars of fire that incinerate everything around. Wires and electrical cables snap, and the city is left without light and communication.

• The Lisbon earthquake (1755) was especially horrific in its consequences. Its force can be judged from the fact that its tremors were felt over an area roughly four times the size of Europe. In Lisbon, enormous fissures up to 5 metres wide separated the centre of the city from the rest of the land. The sea retreated for a moment, but then a vast tsunami engulfed the harbour and the city centre, with water surging up the Tagus River. Almost all the cities of Portugal were destroyed, and Madrid and other cities of Spain were also affected. Thirty-two thousand people perished beneath the ruins of buildings. A sea wave 26 metres high pushed 15 kilometres inland and claimed 60,000 lives. Gradually diminishing in height, this terrible wave travelled along a considerable stretch of the coasts of Europe and Africa. On the island of Madeira it still reached 5–6 metres.
• The Peruvian earthquake (1869) claimed 70,000 lives.
• The most catastrophic earthquake in Peru in terms of casualties occurred in May 1970, with a death toll of 100,000. The whole territory of Peru lies in a seismically hazardous zone. Earthquakes in Peru are the result of the convergence of two lithospheric plates along the ocean coast: the South American Plate overrides the subducting Nazca Plate. Each year the plates converge by 78 mm, and these geological changes are accompanied by earthquakes.
• The Messina earthquake (on the island of Sicily in 1908) was dreadful — 84,000 people perished beneath the ruins of the city. The waterfront and other stretches of shore subsided into the sea.
• In China, in Gansu Province, about 200,000 people died during the earthquake of 1920. Most of them were buried in cave dwellings (dug into loess) that collapsed at the first underground shocks.
• A catastrophic earthquake struck New Zealand in 1931 (on the east coast of the North Island). Several towns were destroyed and burned. The fire broke out because large oil storage tanks were damaged. Along the seashore, numerous landslides and fissures formed over a stretch of 120 kilometres; in places the shore rose and the sea retreated.

A fire after an earthquake

Why are earthquakes so frequent in Japan?

Earthquakes are exceptionally frequent in Japan because the islands sit at the meeting point of several lithospheric plates. During one seven-year period, 8,331 earthquakes were recorded — an average of no fewer than three per day. Major earthquakes occur about once every 6–7 years. Japanese earthquakes are notable for their considerable force and are accompanied by the loss of tens of thousands of lives. For example:

• during the 1703 earthquake in the Tokyo region, 200,000 people perished;
• in 1855, in the same region, 104,000 people;
• on 1 September 1923, 142,000 people.

The 1923 earthquake was especially terrible. After the very first shock, fires broke out in many districts of the Japanese capital. The disabling of the city's water supply and the blocking of streets by ruined buildings created insurmountable obstacles to firefighting. A strong wind spread the seats of the blaze. Over two days the rampaging element destroyed three-quarters of the city already wrecked by the earthquake.

Other towns and settlements within the earthquake zone suffered disasters no less severe. Yokohama was especially hard hit — one of Japan's largest commercial and industrial centres and at the same time the port of Tokyo, as well as a naval base in the southern part of Tokyo Bay that guarded the capital. Huge oil storage facilities served as additional sources of fire in Yokohama.

Many people died from fire and smoke. Streams of hot oil poured into the port, burning the ships that lay there. To these horrors must be added the enormous sea wave caused by the seaquake. It rushed onto the shore, washed away 868 houses and sank eight thousand vessels. A tsunami caused by a seaquake

Subsequent study of the sea floor revealed significant displacements near the eastern coasts of Japan. In addition to the centres mentioned above, the earthquake of 1 September 1923 completely destroyed eight smaller towns and severely damaged eleven more.

The total number of people left homeless and affected by the earthquake exceeded three million. In terms of the scale of destruction, this earthquake surpassed all previous Japanese earthquakes and caused the state losses of 10 billion gold roubles.

• In March 1927 an earthquake of considerable force struck Japan — several thousand people died; then a strong earthquake occurred in May, claiming many lives, and at the same time a powerful earthquake hit western China.
• The earthquake that occurred on 11 March 2011 in north-eastern Japan, with a magnitude of 9.0, is known as the "Great East Japan Earthquake."

This earthquake resulted from the movement of the Pacific and Okhotsk lithospheric plates. It triggered a tsunami whose wave height reached 40 metres in some places. The tsunami caused irreparable destruction at the Fukushima-1 nuclear power plant. About 20,000 people died in this natural disaster. Destruction at the Fukushima-1 nuclear power plant

Study of the geological changes showed that part of northern Japan shifted 2.4 metres towards North America, in the direction of the earthquake's epicentre, and became wider than before. The region closest to the epicentre experienced the greatest displacement. A 400-kilometre stretch of coastline subsided by 0.6 metres, which allowed the tsunami to spread farther and faster inland.

The Pacific Plate shifted eastward by a distance of up to 20 metres.

Which were the strongest earthquakes of the last century?

Over the past century the following earthquakes stood out for their force:

• The Chilean earthquake (early 1939), which destroyed six cities in which tens of thousands of inhabitants perished and hundreds of thousands were left homeless.
• The Erzurum earthquake (in Turkey, at the end of the same year, 1939), with a total death toll of more than 23,000 people.
• The Carpathian earthquake (autumn 1940) covered an enormous area. In the west its boundaries reached the city of Marseille (southern France), in the south Sinop (in Turkey), and in the east Moscow and Voronezh. In Moscow the earthquake's strength was rated at four points (see below).

The Carpathian Mountains are still very young. According to geologists, they formed at the end of the Tertiary period and may even have extended into the beginning of the Quaternary period — that is, the last million years of the Earth's venerable life (more details: How the modern plant world took shape).

That this is indeed the case is attested by numerous traces of displacement — "quite" fresh in geologists' opinion — of both individual sections and the entire mountain system as a whole. Particularly convincing in this respect are the ancient river terraces, located considerably above the present level of the rivers that flow down from the Carpathian Mountains.

Carpathian earthquakes are therefore echoes of a mountain-building process that is not yet entirely complete. The Carpathian earthquake

The epicentre of the powerful Carpathian earthquake of 10 November 1940 fell on the richest Romanian oil-bearing regions of Ploiești and other deposits. The earthquake caused considerable material damage to Bucharest — about a quarter of the city was destroyed — and many other Romanian cities suffered as well.

The captain of the Soviet steamer "Krasny Profintern," which was moored in the Romanian port of Galați, described his impressions as follows:

...For 2–3 minutes the entire hull of the ship shuddered from the shocks. It seemed as though we were in the open sea during the fiercest of storms. The lights in the city went out at once. In the darkness that fell, we could hear the cries of the terror-stricken residents. At dawn we saw great destruction... Almost no whole buildings were left standing in Galați.

The Carpathian earthquake badly affected Chișinău, many districts of Moldova and south-western Ukraine. Its waves rolled all the way to Moscow. Many residents noted in their reports (around 350 letters received by the USSR Academy of Sciences) that they had been woken by the tremors of the earthquake, that hanging lamps swung, crockery rang, furniture creaked, and domestic animals behaved restlessly — especially birds in cages — and so on.

Among later catastrophic earthquakes, two stand out, both occurring at the very end of 1957.

• The first, with a strength of 11 points, occurred in the territory of Mongolia in early December. The earthquake's focus lay in the Gurvan Bogd Mountains (southern Mongolia), roughly 700 kilometres south-west of Irkutsk. This is known as the Gobi-Altai earthquake. On-site studies showed that the mountains were broken by numerous fissures up to 20 metres wide. The main fissure extended for 250 kilometres; in places stepped faults 3 metres high formed. One of the mountain peaks was split in two. A portion of mountain 400 metres high collapsed into a gorge. The whole Ikh Bogd massif, according to researchers, was displaced eastward and somewhat uplifted.
• The second catastrophic earthquake occurred in Iran, in the region of Kermanshah, in mid-December of the same year, 1957. As a result, ten settlements were completely destroyed and thirty were severely damaged; the number of victims is put at 240 people.
• The territory of Iran lies in a seismically hazardous zone, which is why high-magnitude earthquakes are frequent there. The next catastrophic earthquake occurred in 1978, when the city of Tabas was almost completely destroyed.
• And in 1990 a catastrophic earthquake in northern Iran destroyed the towns of Manjil, Rudbar and Lushan and claimed the lives of more than 50,000 people. The epicentre lay at the junction of the Arabian and Eurasian lithospheric plates, which passes through northern Iran. The 7.7-magnitude tremor on the Richter scale struck at half past midnight, which increased the number of casualties.
• The 2003 earthquake also proved catastrophic for Iran. The death toll was around 40,000 people.

Catastrophic earthquakes are accompanied by geological changes across the Iranian Plateau, which is a site of tectonic activity, including active folding, faulting and volcanic eruptions. An earthquake in Iran

Which regions of Eurasia are most prone to earthquakes?

Across Eurasia, the regions most subject to earthquakes are Transcaucasia, Central Asia, Transbaikalia and far-off Kamchatka. Among the strongest earthquakes since the end of the 19th century, the following should be noted:

• The Verny earthquake (the town of Verny, now Almaty) in 1887, in which 330 people died in Verny. In connection with the earthquake, a grand landslide occurred in the Trans-Ili Alatau mountain range, turning a picturesque valley into a desert: for a stretch of two kilometres the forest here was buried beneath a rock scree 200 metres wide and at least 100 metres thick.
• The earthquake in Almaty in 1911 was considerably weaker.
• The Akhalkalaki earthquake (in Transcaucasia) in 1899 — 240 people died.
• The Shemakha earthquake (in Azerbaijan) in 1902 — 86 people died.
• The Andijan earthquake (in Uzbekistan), also in 1902 — 4,500 people and 7,000 head of livestock died. Total losses from this earthquake amounted to 12 million gold roubles.

The year 1927 left grim memories, being particularly rich in earthquakes.

• In February the city of Leninakan was destroyed (in Transcaucasia, now Gyumri).
• At the end of July the first Crimean earthquake gave Crimea a slight shaking.
• Almost immediately afterwards, earthquakes were recorded in Greece and Palestine, especially in Jerusalem.
• In August an earthquake affected the Namangan region (in Uzbekistan).
• In September the southern coast of Crimea as far as Yevpatoria was shaken (the second Crimean earthquake; 65 people died).
• In October an earthquake was recorded in Vienna.

In the interval from 11 to 24 September 1927 (during the second Crimean earthquake), 22 earthquakes were recorded around the globe, of which three were strong and one catastrophic. The total number of shocks of the second Crimean earthquake produced more than 250 marks on seismographs over the course of a month. The overall duration of the Crimean earthquake was about four months.

Earthquakes in Crimea occur fairly often — on average once a year. But the Crimean earthquake of 1927, with a magnitude of 8.8, was especially protracted and, not without reason, badly frightened many people. In Yalta up to 70% of all structures were destroyed, and the material damage came to 25 million roubles.

The reason is that the Crimean Mountains form the northern limb of a fold whose southern half subsided below sea level during the Tertiary period. In connection with this, it has been suggested that the northern limb awaits the same fate, and thus Crimea is threatened with collapse. The Crimean earthquake

The study of the foci, or epicentres (that is, the main areas), of the Crimean earthquake showed that they lie on the sea floor 30 kilometres south of the shore, and that subsidence of southern Crimea continues along the fault line, while the northern limb, on the contrary, is rising. Faults in the Crimean mountains

These conclusions are indeed confirmed by special observations made at the seismic station.

• Among later earthquakes, the grand Chatkal earthquake (1946) must be noted first of all; it encompassed the whole of the Tien Shan and damaged even hundreds of buildings in Tashkent.

Fortunately, the main earthquake zone fell on sparsely populated areas, where the indelible traces of the devastating work of the Earth's depths were imprinted. On the southern slopes of the Chatkal Range the mountains cracked deeply in many places. Individual boulders the size of two- and three-storey houses tumbled down into the valleys, and enormous landslides and rockslides took place.

Masses of earth and stone dammed the turbulent mountain river Naryn for several days in places. Many residents perished in the mountain villages. The Chatkal earthquake

• The Ashgabat earthquake (on the night of 5–6 October 1948) had especially severe consequences, accompanied by considerable destruction of the capital of Turkmenistan. On the slopes of the hills and on the plain, stepped fissures extended for hundreds of metres. The height of the steps was measured in tens of centimetres. The earthquake's focus lay 30 kilometres from the city, in the Kopet Dag Mountains.

An earthquake in the mountains

What are seaquakes and how do they differ from earthquakes?

Seaquakes are vibrations of the Earth's crust that occur not only on land but also in the ocean depths. Sailors have repeatedly observed sudden shocks (while the surface of the water was calm) that even seasoned people accustomed to rolling could barely stay on their feet against.

The changes associated with seaquakes can be judged from the breaking of undersea cables and the emergence of considerable depths as a result of faults and grabens forming on the sea floor. When the cable on the Crete–Zante line broke in 1885, it was established that the sea floor had subsided here by 2,760 metres.

Seaquakes produce enormous breaking waves up to 3.5 metres high, and catastrophic floods strike suddenly.

• Thus, in 1737, in connection with an earthquake and a storm, the water of the Ganges rose 11.5 metres above its level and carried off 300,000 human lives;
• the water rose even higher (by 13 metres) at the mouth of the Brahmaputra in 1876, and 200,000 people died during the flood.

The aftermath of the flood in India