Among
natural disasters, earthquakes rate right up top as the deadliest. Each year
thousands of people are killed or left homeless. Whole families, and by
extension family lines have been lost during these events. Current and historical
records document the effects and aftermaths of these major intrusions of Mother
Nature in the lives of humans.
Since
the Earth is in a dynamic state, changes to its surface through such processes
as land shifts will continue to happen and any communities or infrastructure,
not to mention people it the way will in all likelihood be harmed.
The
1906 earthquake in the San Francisco area, mentioned briefly in my blog post of
18 April 2017, was felt along
the entire north coast of California, particularly devastating the urban area
of San Francisco where it destroyed 80% of the city. Over 3,000 people died as
a result of the quake and its resultant fires.
Major
earthquakes are concentrated along the edges of the Earth’s crustal
plates
where relative movements cause the plates to impinge on each other. California
is a region where the North American and Pacific plates slide laterally in
opposite directions, grinding against each other and creating major fractures
and fault zones. Movement is frequent and never-ending, in a geological sense,
resulting in severe tremors and vertical movement.
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World
map showing major crustal
tectonic plates – source United States Geological Survey
Along
coastal areas tsunamis may form as a result of the shifting of the seabed, adding
a secondary potential for destruction. These large ocean waves can travel
thousands of miles across open water, eventually appearing along distant
shorelines with highly destructive force.
There
is an informative website that lists
earthquakes
by period, country and region and also compares the devastation in terms of
magnitude, cost of damage and numbers of deaths. These are primarily events
that occurred during more recent times and documented in the published
literature. There is no doubt similar events occurred in the past centuries
before mass media. One major difference is in the perceived human toll. The
rapid and large increase in population of the past 150 years has led to more
people and communities being caught up in the destruction with many more deaths
and greater destruction of infrastructure.
Ancient
writings, along with archaeological and geological studies demonstrate the
occurrence of destructive earthquakes going
back thousands
of years many of which affected early communities. Turkey and Syria, for
example, lie at the junction of three crustal plates – African, Arabian and Eurasian
(Anatolian sub-plate). The region has been the site of numerable major
earthquakes and volcanic eruptions over millions of years. Records dating back
a thousand years describe the destruction from these events. Earthquakes
centered near the Greco-Roman city of Antioch, in AD 115 and AD 526 each apparently
resulted in the deaths of hundreds of thousands of people. The deadliest
earthquake in recorded history occurred in Shaanxi, China
in AD 1556
when over 830,000 people were killed.
Besides
the well-documented 1906 San Francisco event, there have been many major
earthquakes in North America including one in AD 1700 in
Cascadia
(Washington State & British Columbia). No written records exist from the
time period in North America describing the earthquake, however, in Japan there
are reports of a tsunami thought to have originated along the North American
coast. Tree ring evidence from the Pacific Northwest also show a major
disruption in forest growth from flooding of low-lying areas. The earthquake is
believed to have been caused by the North American plate slipping over the Juan
de Fuca plate with a major shift along the deep subduction zone.
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Structure of the
Cascadia region
and history of major earthquakes – source United States Geological Survey
While
earthquakes by themselves may not have been the primary reasons for the
migration of people, they certainly have been the cause of the deaths of
thousands and the early demise of family lines. Family historians may wish to
look at natural disasters such as earthquakes when studying the reasons why
ancestors died or moved. Such natural phenomena are often part of the stories
about families.
