This week we're going to discuss earthquakes. An earthquake is a shaking of the earth's surface caused by a release of energy which creates seismic waves. Earthquakes are caused by the breaking and shifting of rock beneath the earth's surface. They usually occur along fault lines, or cracks that occur within the Earth’s crust.
Worldwide, people feel an estimated 1 million earthquakes a year. (Keller 53) The magnitude of an earthquake is a measured value of the
earthquake size. Most people who live in California are familiar with earthquakes and their damage due to the San Andreas fault line running through the state but there are many countries where earthquakes are not such a concern to the residents.
Even though Iceland is a very seismically active country they've only had a few large earthquakes in the past 50 years. They had a big (over M5.9) earthquake in 2008 where only 30 people were injured with no human fatalities reported (a number of sheep perished though). That earthquake registered in at M6.1 and caused some structural damage to the towns around the epicenter. In June 2000 they were also hit with two earthquakes (one recorded as a M6.6 and one at M6.5) a few days apart, but even then the damage was more to their road and older building infrastructure and again there were no casualties.
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| June 2000 earthquake |
You can check out Iceland's earthquake activity by visiting the Iceland Met page. It gives a really great summary of the last 48 hours of seismic activity for Iceland. It also gives you a really good summary of the activity per week. Just in the week of February 1-7th they measured 350 different earthquakes but none of them registered over M3.1 which seems to be the normal for Iceland. Because of it's location on the Mid Atlantic Ridge and it's proximity to two tectonic plate boundaries, Iceland is an area prone to volcanoes and earthquakes but big earthquakes are rare.
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| Activity 02/14-02/16/16 |
The largest earthquakes in Iceland occur within transform zones which connect the north east volcanic zones and eastern volcanic zones of the island with the active ocean ridge off shore (the Tjornes Fracture Zone (TFZ) and South Iceland Seismic Zone (SISZ)) and at the centre of the island at the junction between three volcanic zones. The SISZ is the most seismic active zone in Northern Europe.
As
few injuries resulted from the June 2000 earthquakes, a blasé attitude
may exist that earthquake vulnerability is low and that earthquakes are a
bit of fun to experience once in a while. Iceland's attitude towards earthquakes appears (to me) to be pretty laid back. They do take some precautionary measures such as awareness and preparedness guidelines for earthquakes though, because they can cause landslides and rocks to fall and many homes are built at the base of steep mountains. Also, for Iceland, often times an earthquake is accompanied by volcanic activity. Iceland's warning systems and awareness campaigns focus mostly on volcanic activity (which we'll discuss in week five) and they don't put as much concern into risk assessment and preparedness for an earthquake. Their Civil Protection Department website does list preventative measures for a number of situations and they suggest the same Duck, Cover, Hold technique that we teach in the US.
As to structural reinforcement in Iceland, they already construct many of their buildings to withstand an earthquake. According to the OECD, after devastating earthquakes in 1896 and 1929, reinforced buildings became the usual standard for construction. "Engineers recognised the importance of reinforcing concrete with steel bars as well as the continuity built into concrete structures poured in situ." (OECD) After 1976 Iceland also used the California Uniform Building Code as a model for construction although now they are moving towards the Eurocode 8 for their seismic design. (OECD) Accordingly, this has lowered the chance of major structural damage from future earthquakes.
Works cited:
Keller, Edward and Duane DeVecchio. Natural Hazards. New Jersey: Prentice, 2012. Print.
OECD. Educational Facilities and Risk Management Natural Disasters: Natural Disasters. France: OECD Publication. 2004. Print.
link to ebook (I specifically used page 86 for information)
Images:
2000 earthquake image: uk/Tectonics%20and%20Seismicity%20in%20Iceland/Inrtoduction.html
Map of Iceland earthquake activity:
http://en.vedur.is/
Thanks for reading!!
Jennifer
This week we're exploring plate boundaries and plate tectonics for our chosen country.
Plate Tectonics is the scientific theory that explains the motion of the Earth's lithosphere and subsequent earth processes that the plate movement causes. Tectonic processes are driven by forces within the Earth (Keller 29) The earth's lithosphere consists of 7 or 8 major plates and a few minor ones. Where these plates meet establishes the plate boundaries which can be divergent, convergent or transform depending on their movement. Earthquakes, volcanic activity and mountain ranges are some of the results of these plate boundaries shifting. Despite the natural processes that occur, the tectonic cycle is important to our lives. Everything living on Earth is affected by plate tectonics.(Keller 46) The movement of the plates also produces areas of natural resources, like gas and minerals, that we depend on.
Iceland is a fascinating country in regard to it's plate boundaries and tectonics. The main thing you should know is that Iceland is on a divergent plate boundary. It traverses the Mid-Atlantic Ridge tectonic plate boundary which separates the Eurasian and the North American plates. There are many places on Earth where plates move apart but most of those are deep underwater. Due to the Mid-Atlantic ridge running right through the middle of Iceland you are offered a rare chance to see plate tectonics occurring above sea level. In fact, it is probably the only place in the world where the effects of two major tectonic plates drifting apart can easily be observed above sea level.
This photo is of Þingvellir (Thingvellir) in Iceland. As you can see, the continental rift runs right through it, the largest area, Almannagjá, is so large it is an actual canyon.
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| Thingvellir |
Due to this divergent plate boundary, at some point (not in our lifetime)Iceland will split apart. Right now the plates are moving apart at about 1cm each year but as North America moves westward and Eurasia eastward, new crust is formed on both sides of the diverging boundary. While the creation of new crust adds mass to Iceland on both sides of the boundary, it also creates a rift along the boundary. Iceland will inevitably break apart into two separate land masses at some point in the future, as the Atlantic waters eventually rush in to fill the widening and deepening space between. This widening rift and location on the Mid-Atlantic Ridge makes Iceland very active with volcanic and earthquake activity.
Works Cited
Keller, Edward and Duane DeVecchio. Natural Hazards. New Jersey: Prentice, 2012. Print.
Photo credits:
Map of plate boundaries: http://newsimg.bbc.co.uk/media/images/47820000/gif/_47820856_iceland_tectonic_466_2.gif
Image of Þingvellir : http://www.opinion250.com/images/Thingvellir.jpg
Thanks for reading.
Jennifer
Hazards. Disasters. Catastrophes
In the geological world the natural process, anything produced by nature, can result in any number of natural hazards. A hazard is any natural occurring action that results in harm to human life or property and is often the result of misuse
of the land by humans. This includes earthquakes, floods, volcanic
activity,and so on. When these hazards happen over a short period of
time, in one small area this becomes a disaster rather than just a
hazard. Natural disasters are defined by 4 criteria: 10 or more people
killed, 100 or more people affected, a state of emergency is announced
and international support is requested. An example of a natural disaster
would be the 2013 tornado that hit Moore, Oklahoma. If the
disaster is extensive, one that includes a large output of money and
involves a very long recovery time, sometimes years, then that natural
disaster becomes a catastrophe. Hurricane Katrina is an example
of a catastrophe. Hurricane Katrina was the costliest catastrophe in US History along with one of the deadliest. Recovery in that area was long and is still ongoing today.
For
this class I will be discussing Iceland and the affects that different
natural hazards have on this country. For those that are not familiar
with this country, Iceland is a Nordic island located between the North
Atlantic ocean and the Arctic Ocean. Known for it's beautiful landscapes of
glaciers and waterfalls, Iceland is also very active geologically. It sits on the boundary of the
Eurasian and North American continental plates, which are slowly moving
apart a little each year. It's also located on the Mid Atlantic Ridge and the Icelandic plume, a hotspot, which makes Iceland very active with volcano and geothermal activity. The greatest hazards, geologically, for Iceland are volcanoes and earthquakes. I am really excited to learn more about Iceland geologically as my husband and I will be visiting there later this year. A number of the geological attributes of Iceland are what attracted us to the country in the first place.
Photo credit
Map of Iceland: Eyjafjallajökull volcano: volcanoes and glaciers of Iceland. Map/Still.
Britannica Online for Kids. Web.
4 Feb. 2016.
<http://kids.britannica.com/elementary/art-141901>.
Thanks for reading!
Jennifer
