Geology Home Page physical geology historical geology planetary gems
Roger Weller, geology instructor
by Kelli Patterson
Rock Slides: Flim Mountain
Rock slides are one of the many natural disasters anyone can ever experience. When you have a rock slide it can happen anywhere at anytime the rocks want to give way. When you live in the United States of America most people expect them to happen in California where there are many rocks and sediments waiting to tumble near the coast line. When rock slides happen you can hear the rumble of the rocks falling down the mountainside even from a great distance. There was a time a few years ago where I personally had an experience with a rockslide in Arizona at Colorado national park. When one went up the mountain you could observe and tell where the rocks had fallen out of place from the rest of the sediment. Boulders had moved trees and other debris out of the way, when I observed this I could still hear the rumble of all the rocks hitting against each other as there was still loose rock on the Cliffside. That rockslide was caused by a gratuitous amount of rainfall, but rain is not the only factor that can cause such devastating rockslides.
Rockslides are characterized by the rapid downward
movements of newly detached segments of bedrock; it can also create rock masses
that hold a certain position due to these geologic movements. The main causes of
rockslides are mainly erosion and earthquakes, yet massive rainfall and glacier
melting can also be causes( they are rarer in certain places of the world). The
effects of a rock slide can go from no damage at all to catastrophic. As you can
see rock slides are very dangerous. Just like the rock slide that happened in
the Flim Mountain in the Alps, some 10,000 years ago. The last time the slide
was measured the top was about 8,858 feet above the sea level. Then the end of
the slide lies about 1,100 feet. The debris was put back together due to the
pressure of the rock slide. As it baked it back together, it became more of a
solid rock. Now letís take journey to the Flim mountain.
In the Alps of Switzerland there is a flimsersten mountain with the coordinates of 46 degrees and 50' north by 9 degrees 17' East with an elevation of 1081 feet. Flim is an area of 50.5 Km that is split up in to different areas. 33.7% of the land is used for agricultural purpose, 28.9% is forested, 3.6% is settled and the other 33.9% is non-productive. The town of Flim can be found at the line where the slip surfaces the displacement if a landslide. There was so much debris that the Rhine river actually cuts though apart of the mountain. The top of the rock slide measures out to be 8,880 feet above sea level.
The climate was not the trigger but it played a big part in it. Rock slides control morphological landscape evolution, and then the Flim rock slide represented a major natural hazard. the Flim rock slide was believed to be attributed to the late glacial period, the glacial period was thousands of years in the ice age that were marked by the colder temperature. The last know glacial period know that happened ended about 15, 000 years ago. According to Pleistocene epoch which began about 70,000 years ago, when the last glacial period covered most of the northern hemisphere.
The estimated volume of the rock slide was at 8 Km3. Covering a surface of about 52 Km2. the Rock slide happened in one great stroke. When the Flim rock slide happened it was mostly made of Jurassic and cretaceous limestone. Jurassic is mostly found in directly northwest of the Triassic area. In Jurassic you can find between 30 and 35 percent iron. Then you have Cretaceous limestone which is found all over the world. Most limestone is marine deposits, but there are some that are formed in lakes and rivers. Then layers f the rock slide is almost parallel to the slope. An interesting fact about the rock slide is that the main body did not spread out side to side. That is why the primary structure of the mountain is still so well preserved.
Predicting a rock slide is just as hard as predicting
when an earthquake is going to happen. Rock slides happen all over the United
States as well. the main place tthat they happen is the costal and mountainous
areas. Such as California, Oregon and Washington. Even though slides happen all
over the world there is six different types of slides. There are slides, the
falls, the topples, the flows, and lateral spreads. when you have a slide there
has to be a cause to it all you can have a geological cause those are caused by
weak or sensitive materials, weathered materials, sheared jointed or fissured
materials, adversely oriented discontinuity and contrast in permeability or
stiffness of materials. Then you have morphological causes, which could be
caused by tectonic or volcanism uplift, glacial rebound. It can also be caused
by fluvial, wave, or glacial erosion subterranean erosion deposition loading
slop vegetation removal, thawing, freezing and thaw weather and finally shrink
and swell weather. Then people think that people can not cause a slide but it is
possible, some f the causes of a man made slide is excavation of slope or its
toe, loading of the slope or the crest. Drawdown, deforestation, irrigation,
mining. There is also artificial vibration and water leakage from utilities.
So in conclusion rock slides can be caused by allot of different things, the one that happened in the Alps in the Flim mountains was no exception to the rule. Even though it was it have been the best preserved. It happened over 10,000 years ago and you can still see it today. Looking it up on line allot of people have turned it into a tourist attraction. They have built restaurants and hotels on the top of the mountain over looking the rock slide. Also when you have a rock slide rock from millions of years ago can be exposed, if that happens it a good way for geologist to learn what the earth was like back then. So if you ever want to see a rock slide that happened over 10, 00 years ago, grab a map and go to the coordinates of 46 degrees 50' north a degrees 17í East and you will find a very pretty one.
(all pictures can be found through the websites below)