title.jpg


Where:
The land slide occurred in this small town in Nachterstedt, Germany, which is also apart of Seeland. This landslide happened on the lake of Concordia which was about 100 ft deep and covers 865 acres in Germany. In 1959 a much larger slide occurred in the same place resulting in a higher number of deaths. This disaster happened on July 18, 2009 around 5am. The landslide occurred over a 350 meter stretch of shoreline which gave way and took two homes along with it. After landslide water level rose 2ft than what it was before.



(Figure1-"Losing Hope After Nachterstedt Mudslide" Übermensch Undermined (03/25/2008)man_made_lake.jpg


Causes of Event:
The major cause of this event was that is was made into a lake by man.(fig 1) The lake was filled through rains that Nachterstedt had throughout the years. Heavy rains were recorded in June the month before. This trigged many
reasons for the landslide that occurred on this morning in Nachterstedt. Two Scientists believed that this occurred due to a recorded earthquake of a 1.0 on the Richter Scale, just a few minutes before the land gave way. However, in 1994 they decided to make a lake out of what used to be a pit mine. From the years of 1865 until 1990 brown coal was mined from this area. Some believe that there could be old shafts that were not discovered or mapped out. Therefore many other scientists believe that this landslide was not caused for the 1.0 underground movement, but rather from the a tunnel collapsing in what used to be the old mining tunnel. Another main reason many come up with is liquefaction. Liquefaction occurs in saturated soils which is completely filled with water. During an earthquake the soilis less stiff and the strength of the soil becomes weak due to the shaking of the earth. Many believe this reason because since the ground beneath was already weak for the mining tunnels, the earthquake trigged the slide. People are still trying to determine the main cause of this disaster. There are many different scientist who believe in one reason or another, but one final one has not been determine still to this day. I believe all three of these reasons caused the earth to crumble that one morning in Nachterstedt.


nachterstedtneu_HA__140325c.jpg
(Figure 2-"Losing Hope After Nachterstedt Mudslide" Übermensch Undermined (03/25/2008)
This house was one of the hosues which was cut in half due to this landslide.(fig 2) Three people that lived in this house went missing for days until pronounced dead. One cat was seen coming out of the rocks and debris. One of the few survivors.


debris_slide[1].jpg
(Figure 3-"Debris Slide" J. Appleby, R. Kilbourne, and
C. Wills after Varnes, 1978-)

Type of Mass Movement:
This type of mass movement was a debris slide which typically occur on slopes which tend to have a very steep slope. What may also cause such a slide is heavy rainstorm or series of storms which deliver enough rain to trigger debris slides. “Natural erosion at the base of debris slide scars may trigger additional slides. Cutting into the base of a debris slide scar may also trigger renewed slides.” Which was experienced from the previuos slide and trigged the one in 09’. (fig3)




Preventions:
We have learned about a few preventions in class that has made us aware of hints of mass movement. One prevention we have learned is to be the most cautious and not buy a house on a hill, yet this is unlikely sometimes because many people think that something like a landslide can never happen to them. In these situations then we must do the following. The first this to do is obtain geologic information and maps around the areas of potential slope instability. Someone can also check and maintain the drainage systems around your home, thus practicing water conservation.


The original hypothesis that a magnitude 1.0 earthquake may have caused the landslide has been ruled out. This forces scientists to look for other causes. The general consensus is that the coal mining that occurred in the area between 1865 and 1990 may be to blame (source). Tunnels were built underground all over this area, and a man-made lake was created in 1991. This landslide could have been prevented if scientists and engineers had used more caution when building on this unstable land. They knew that the area had been used extensively for coal mining, so proper measures should have been taken before construction to make sure that the land was stabilized. Hopefully this disaster will be the push that they need to reinforce the landscape in order to prevent future tragedies.




SOURCES:
Clues emerge on cause of Nachterstedt landslide,8 Aug 09- http://www.thelocal.de/national/20090808-21123.html

http://3dparks.wr.usgs.gov/landslide/types.htm


http://daveslandslideblog.blogspot.com/2009/07/update-nachterstedt-landslide.html

http://www.consrv.ca.gov/cgs/geologic_hazards/landslides/Pages/index.aspx


http://www.ussartf.org/landslides.htm