Seismic
events include earthquakes, volcano eruptions, landslides and
shockwaves that can in turn trigger tsunamis, avalanches and further
seismic events.
People are changing the climate and this can
trigger seismic events. Earthquakes can be triggered in a number of
ways, including the following:
• Earthquakes can be
triggered by fracking and by waste pits and pools associated with
fracking.
See the article
at:
•
Warming caused by people makes snow and ice melt, removing weight
off the land and dumping it into the sea. This change in weight can
trigger earthquakes.
•
The Earth's crust can be flexed by storms. Large cyclones first suck
up water, making sea level retreat and lifting up the crust. Then, a
surge follows, while huge amounts of rainwater can add further
weight, pushing the crust down again. This change can be felt over
longer distances, triggering earthquakes across continents. See the
post
at:https://arctic-news.blogspot.com/2017/09/extreme-weather-is-upon-us.html
•
Wild weather swings can be the result of changes in the jet streams
caused by global warming. Huge sudden swings in temperature and in
air pressure can make soils and ice go abruptly from expansion to
compression and back again, which can cause cracks and landslides,
and associated shockwaves, which can in turn trigger larger seismic
events and open up methane craters with can come with large releases
of methane. See the segment further below on 'Earthquakes and
Extreme Weather Events'.
• War and explosions associated with
testing of new weapons could also trigger seismic events, as
discussed e.g. at:
In
turn, earthquakes can cause clathrate destabilization, resulting in
methane releases. Below are discussions of links between seismic
events in the Arctic and methane releases.
Earthquakes and
Methane
An earthquake hit the Arctic Ocean with a
magnitude of 4.7 on the Richter scale on July 12, 2016. High levels
of methane showed up in the atmosphere on July 15, 2016, over the
area where the earthquake hit.
From:
Some
of the earthquakes occurring in 2014 were discussed in specific
posts:
• M4.6
- North of Franz Josef Land,
2014-04-13 02:12:19 UTC, discussed in this
post
• M4.2
- North of Franz Josef Land,
2014-04-04 07:01:30 UTC
• M4.4
- 262km NE of Nord, Greenland,
2014-04-22 10:30:23 UTC, discussed in this
post
• M4.3
- 148km SSE of Longyearbyen, Svalbard,
2014-04-24 08:33:06 UTC
• M5.1
- Greenland Sea,
2014-04-26 03:55:33 UTC, discussed in this
post
•
M4.5 - Gakkel Ridge, 2014-03-06 11:17.17.0 UTC, discussed in this
post
As
melting of the Greenland Ice Sheet speeds up, isostatic rebound
could cause earthquakes around Greenland to become stronger and
occur more frequently. Earthquakes in this region are very worrying,
as they can destabilize hydrates contained in the sediment under the
seafloor of the Arctic Ocean. Furthermore, one earthquake can
trigger further earthquakes, especially at locations closeby on the
same faultline.
From:
Earthquakes
and Extreme Weather Events
An
earthquake with a magnitude of 4.6 on the Richter scale hit Baffin
Island on February 12, 2015, at 02:11:40 (UTC). The image below,
from the United
States Geological Survey (USGS),
shows the epicenter of the quake.
The
earthquake occurred at a time when surface temperature anomalies
over parts of North America and Greenland are at the bottom end of
the scale, while surface temperature anomalies over parts of Siberia
are at the top end of the scale, as illustrated by the image below.
The
image below shows pressure differences reaching the top and bottom
ends of the scale (left). At the same time, sea surface temperature
anomalies around North America and Greenland are at the top end of
the scale (right). It appears that something had to give.
This
earthquake is important, given that it hit an area without large
faultlines (though earthquakes are common here, also see this
discussion).
The Baffin Island earthquake occurred in an area prone to glacial
isostatic adjustment, as illustrated by the image below.
|
|
From
"http://grace.jpl.nasa.gov", (unfiltered version).
Credit: A, G., J. Wahr, and S. Zhong (2013) "Computations of
the viscoelastic response of a 3-D compressible Earth to surface
loading: an application to Glacial Isostatic
Adjustment in
Antarctica and Canada", Geophys. J. Int., 192, 557–572,
doi: 10.1093/gji/ggs030
|
Glacial
isostatic adjustment as a phenomenon takes place over relatively
long periods. An additional problem is extreme weather events
influencing the occurence of earthquakes more immediately.
Five
earthquakes occured on February 13, 2015, closely after each other
together:
• M5.3 Northern Mid-Atlantic Ridge 2015-02-13
18:48:16 UTC 10.0 km
• M4.9 Northern Mid-Atlantic Ridge
2015-02-13 18:58:06 UTC 10.0 km
• M7.1
Northern Mid-Atlantic Ridge 2015-02-13
18:59:12 UTC 13.8 km, south of Greenland
• M4.7 Reykjanes Ridge
2015-02-13 21:25:18 UTC 10.0 km
• M5.2 Reykjanes Ridge
2015-02-13 19:33:10 UTC 14.2 km
The M7.1 is the largest
earthquake to hit the area around Greenland in a decade or more. And
it's not just this one that has recently hit the area. The image
below shows the February 12, 2015. Baffin Island quake in yellow,
and the earthquakes that occurred on February 13, 2015, at the
Northern Mid-Atlantic Ridge in orange. Furthermore, there are recent
quakes on Iceland in orange and yellow. There were also three large
earthquakes in the Greenland Sea, the 4.6 one is highlighted in blue
(otherwise it would have been hidden).
The
image below gives an impression of extreme weather events on
February 13-14, 2015.
Links
between extreme weather events and earthquakes have been discussed
before.
Extreme weather events look set to intensify as temperatures in the
Arctic keep rising. This is very worrying, given the vulnerability
of methane under the seafloor of the Arctic Ocean. Furthermore,
there are also indications that methane
could be released from Greenland due
to sequences of strong compaction and expansion of the snow and ice
cover, due to extreme weather events.
High methane
levels have recently been recorded in the atmosphere over the Arctic
Ocean, including over Baffin Bay.
Methane
is present in sediments under the Arctic Ocean in the form of free
gas and hydrates. Earthquakes can send out strong tremors through
the sediment and shockwaves through the water, which can trigger
further earthquakes, landslides and destabilization of methane
hydrates.
As temperatures in the Arctic keep rising, the jet
streams and polar vortex are changing their shape, in particular
becoming more wavy, which can cause more extreme weather events such
as the events described above.
From:
Methane
Release caused by Earthquakes
Methane
hydrates can become destabilized due to changes in temperature or
pressure, as a result of earthquakes and shockwaves accompanying
them, severe storms, volcanic activity, coastal collapse and
landslides. As an example, an earthquake followed by methane release
was discussed in the post Sea
of Okhotsk a
few months back. Such events can be both primed and triggered by
global warming, particularly in the Arctic, as follows:
As
more ice melts away on Greenland and more water runs off into the
sea, there is less weight on the Earth’s crust under Greenland.
The crust and mantle can bounce back during a large melt, an effect
that is called 'isostatic rebound'. This rebound can not only
trigger earthquakes and landslides, it can also suck up the magma
in the Earth’s crust to the surface and trigger volcanic
eruptions.
The
added weight of water from melting glaciers stresses the Earth’s
crust underneath the sea, which can cause earthquakes. This is
especially the case for coastal waters, where the impact of the
water that flows into the sea is huge, not only in terms of weight,
but also in terms of the currents they cause.
As
the permafrost melts, mountain ranges, soil and submarine sediments
all become less robust. Where the permafrost previously held things
together, we can now expect more coastal collapse, avalanches and
landslides, which can send shockwaves through the sea that in turn
trigger earthquakes and hydrate destabilization.
Methane
hydrates that are on the edge of stabilization can be disturbed by
global warming in two additional ways, temperature and pressure:
Warming of the Earth's crust as heat penetrates sediments on the
seafloor. Thermal expansion of the Earth's crust means that the
crust will expand slightly in volume, resulting in expansion of the
cavity that holds the hydrates.
Finally,
there's the additional impact of methane itself. Permafrost
previously kept methane stable in sediments. Methane converting
from hydrates into free gas will expand some 160 times in volume;
this explosive process can trigger further destabilization. Once
released into the atmosphere, the methane has a huge local warming
potential, adding to the threat that further methane releases will
occur locally.
Back
in 2006, Bill McGuire said:
"A particular worry is that this in turn will contribute to
large-scale releases of methane gas from the solid gas hydrate
deposits that are trapped in marine sediments. Gas hydrates have
been identified around the margins of all the ocean basins, and
outbursts of gas may occur as sea temperatures climb or as rising
sea levels trigger underwater quakes in the vicinity."
For
more than a decade, Malcolm Light, contributor to the Arctic-news
blog, has been warning about the danger of methane hydrate
destabilization due to earthquakes (see the poster at the bottom of
the page on seismic
activity).
With
this in mind, let's take a look at a picture of Earth.
|
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September
13, 2013, 3am - Sep 14, 2013 1am
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The
large number of yellow spots in the top left corner are related to
the flooding in
the Basin of the Amur River (Heilong Jiang). Such extreme weather
events are becoming ever more prominent, due to global warming and
the feedbacks such as methane releases. Similarly, extreme weather
events such as droughts and heatwaves lead to wildfires that also
produce large amounts of methane.
The image only shows the
Northern Hemisphere, but on the Southern Hemisphere, high levels of
methane have been recorded for a long time on Antarctica. While huge
amounts of snow fall on Antartica, the amount of snow and ice that
melts each year is even larger, widening the difference between the
weight the snow and ice exercize between periods. This difference in
weight could similarly cause rebounds of the Earth's crust, sucking
up the magma and causing methane hydrates to be destabilized, as
described in the earlier post Antarctic
methane peaks at 2249 ppb.
The
image also shows fault lines. Several yellow spots are present on
the fault line over the Arctic, including some that point at the
coast of Norway; they appear to be caused by seismic activity along
the fault line, as discussed in the recent post Methane
reaches 2571 ppb.
Meanwhile,
methane readings peaked at 2416 ppb on September 14, 2013. Very
worrying are also the high methane readings close to the Gakkel
Ridge, the fault line at the center of the Arctic Ocean, and the
spots closer to the Laptev Sea.
Finally, there are high
readings along the Aleutian
Islands,
Alaska. The islands, with their 57 volcanoes, are in the northern
part of the Pacific
Ring of Fire and
they have experienced a lot of seismic activity lately, including an
earthquake with a magnitude of 7 on the Richter scale on August
30, 2013,
and several more recent earthquakes with a higher magnitude than 6
on the Richter scale.
[Editor: The images below, added
September 24 and 26, 2013, show high methane releases at a spot just
north of Greenland that was hit by an earthquake with a magnitude of
4.5 on the Richter scale on September 1, 2013, as also discussed in
the post Methane
reaches 2571 ppb.
The two bottom images also show the magnitude 5 earthquake that hit
Russia on September 24, 2013.]
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September
20, 2013, 11am - Sep 22, 2013 3pm [ click on image
to enlarge ]
|
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Sept.
25, 2013 am - the orange spot just north of Greenland indicates
a recent earthquake [ click on image to enlarge ]
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Map
specifying details of two recent earthquakes. Size of spots
indicating earthquakes on the map is relative
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Methane,
Faults and Sea Ice
The animation below illustrates links
between:
The
fault line that crosses the Arctic Ocean and forms the boundery
between two tectonic plates (i.e. the North American Plate and the
Eurasian Plate)
Arctic
sea ice, which until now has acted as a shield
The
prominence of high methane readings over the Arctic Ocean
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[
this animation is a 1.67 MB file that may take some time to
fully load ]
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Above
animation illustrates high methane readings (1950 ppb and higher, in
yellow) prominently showing up within the bounderies of the sea ice,
and especially along the Gakkel Ridge and Laptev Sea Rift parts of
the fault line that crosses the Arctic Ocean.
From:
•
Methane, Faults and Sea
Icehttp://arctic-news.blogspot.com/2013/11/methane-faults-and-sea-ice.html
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