The offset, white stalagmites were about two inches tall and were growing on taller, brown stalagmites throughout both caves. When he and his colleagues spotted similar stalagmites pairings in caves in two other Midwestern states, they decided to investigate.
Sticks and Slips
Using rock dating techniques, the scientists calculated the ages of the new stalagmite growths, and were surprised to find that they were all roughly years old. An idea began to form in the scientists' minds: perhaps the stalagmite pairs they had uncovered were due to earthquakes disrupting the normal stalagmite-formation process.
Stalagmites are formed by mineralized water droplets falling from cave ceilings, and earthquakes could leave their mark on stalagmite growth by shifting the ground and altering the flow of a water drip. In a new study, published in the September 13 issue of the Bulletin of the Seismological Society of America , Panno and his team tested this hypothesis. The scientists used a variety of dating techniques to determine the ages of new stalagmite growths in several caves in the Wabash Valley fault system in the Midwestern United States, and compared them to the timing of known earthquakes in the region.
Earthquakes shaped ancient Greek culture | EARTH Magazine
Among four stalagmites in Donnehue cave in Indiana, the scientists found a twin pair stalagmite pair that had stopped growing around , years ago and then resumed growth again around 6, years ago, overlapping with a roughly magnitude 7 earthquake in the region. Another younger stalagmite began growing around 1, years ago—coinciding with a magnitude 6.
Scientists already knew about both of these ancient quakes from other studies of shaken soil in ancient sediments. Tinsley added that because stalagmite growth can also be affected by other factors, such as climate change that causes a drip source to dry up, building a strong case for ancient quakes that aren't already known about will require finding multiple stalagmite pairs of similar ages in multiple caves.
Indeed, Panno says that most of the stalagmite shifts his team observed were related to flooding or climate change, but the new study demonstrates that it's possible to disentangle these effects from those triggered by earthquakes.
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The premise here is that great earthquakes should trigger landslides. Landslides could block streams and drown forests — or dump trees into a lake. Sherrod said previous studies have established pretty well that the offshore Cascadia fault zone generates a magnitude eight or nine megaquake about every years on average.
Black said the wood samples he has analyzed so far are well preserved. The capital of Balochistan province was severely damaged in the most destructive quake to hit South Asia in the 20th century.
Ashgabat , Turkmenistan. The largest quake ever recorded in South Asia killed relatively few people in a lightly populated region along the Indo-Chinese border. Valdivia and Puerto Montt , Chile. The Chile earthquake of , the largest quake ever recorded in the world, produced a tsunami that crossed the Pacific Ocean to Japan, where it killed more than people.
Prince William Sound , Alaska, U.
Anchorage , Seward , and Valdez were damaged, but most deaths in the Alaska earthquake of were caused by tsunamis in Alaska and as far away as California. Most of the damage and loss of life resulting from the Ancash earthquake of was caused by landslides and the collapse of poorly constructed buildings. The centre of the capital of Nicaragua was almost completely destroyed; the business section was later rebuilt some 6 miles 10 km away.
Guatemala City , Guatemala. Rebuilt following a series of devastating quakes in —18, the capital of Guatemala again suffered great destruction. In the Tangshan earthquake of , this industrial city was almost completely destroyed in the worst earthquake disaster in modern history. The earthquake struck near the border between Colombia and Ecuador on the Pacific coast, producing foot 3-metre tsunami waves. The centre of Mexico City, built largely on the soft subsoil of an ancient lake, suffered great damage in the Mexico City earthquake of Spitak and Gyumri , Armenia.
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Centred in the urbanized San Fernando Valley , the Northridge earthquake of collapsed freeways and some buildings, but damage was limited by earthquake-resistant construction. The Great Hanshin Earthquake destroyed or damaged , buildings and left , people homeless. Nan-t'ou county, Taiwan. The Taiwan earthquake of , the worst to hit Taiwan since , provided a wealth of digitized data for seismic and engineering studies.
Bhuj , Gujarat state, India. The Bhuj earthquake of , possibly the deadliest ever to hit India, was felt across India and Pakistan.
List of historical earthquakes
This ancient Silk Road fortress city, built mostly of mud brick, was almost completely destroyed. Aceh province, Sumatra, Indonesia. The deaths resulting from this offshore quake actually were caused by a tsunami originating in the Indian Ocean that, in addition to killing more than , in Indonesia, killed people as far away as Sri Lanka and Somalia. Azad Kashmir Pakistani-administered Kashmir.
The Kashmir earthquake of , perhaps the deadliest shock ever to strike South Asia, left hundreds of thousands of people exposed to the coming winter weather. The Yogyakarta earthquake injured nearly 40, people and destroyed or damaged nearly , homes in the Bantul-Yogyakarta area. Sichuan province, China. The Sichuan earthquake of left over five million people homeless across the region, and over half of Beichuan city was destroyed by the initial seismic event and the release of water from a lake formed by nearby landslides.
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