Imagine that you are walking to your house after work hours one evening. Everything seems okay, the sun is already setting, and the wind is just blowing at the right speed. The days just seems so perfect. Just a little distance to your house you notice cracks and holes on the road, cracks and holes you are 100% sure that it wasn't there on your way to work. Well you thought to yourself "maybe an accident occurred while you were away". On getting close to the house, you still notice that all the trees close to your house suddenly seem to be leaning in one direction, even the electric pole too. Yet, you still discard it as nothing "It's the wind after all, I will inform the power distribution company later".
On getting to the stairs, it seems as if it is pulling away from the wall. You immediately made a note in your mind to sue the civil engineer that you gave the contract to build the house for you. You then, went into the house, took your bath and immediately went to sleep. Goodnight.
As you slept, you heard an unusual but low sounds from your dream, then series of knocks, "Mike, wake up, wake up". But you were too tired to wake up. "Just give me a break", you thought. Then the sound becomes louder, and louder till it begins to sound as if the whole world is being rolled like a mat.
With all your strength, with only your night wear on, you ran to the window to see what is making that loud noise. At first you can't see it, few minutes later there it comes, a large flow of a mixture of stones, water, rocks, sand, a large amount of refuse and . . . . . your neighbor's house, coming towards you like a very large flood with great fury, blocking every path and you got no way to escape.
[Source](https://serc.carleton.edu/NAGTWorkshops/hazards/events/oso2014.html)
What you just imagined now, is not even close to what some people experienced when they had an encounter with a landslide. In this article I will be writing on what causes landslides, the different types of landslide and what to do during a landslide. I know, I owe you an apology, I haven't been active for sometime now, it wasn't really my fault. I had lots of exam to write, these past week. I had to give it all my time, thanks to God, it's over. Don't worry, I will try to make this article very interesting, I promise.
**LANDSLIDE**
Landslide is a general term which covers a wide range of ground movement which includes rockfalls, shallow flows of debris, failure of slopes and other forms of mass wasting. Due to the fact that it occurs more like muds 'slipping', it is also referred to as landslip or a mudslide. I guess you must have assumed that since it is referred to as Landslide, it must occur on land. Nope, it doesn't mean that. Landslides also occurs at seas and oceans floors. In an act to kinda differentiate them, when it occur in ocean and sea floors, we call them submarine landslide. Landslides are not the same as mudflows. Mudflows are more like a mass wasting that involves the rapid flow of debris that has already been turned to liquid (either completely or partially) by a water source.
Before a landslide occurs, something must trigger it. Primarily, landslides are prompted mainly by the action of gravity, but that doesn't mean that landslides are solely caused by gravity, there are several factors that contributes to its occurrence. To better understand this, let see these factors as "the constituent of a bomb", while gravity acts as the detonator.
**CAUSES**
Due to the fact that landslides occur quite frequently, and whenever it occurs, it leaves destruction in its wake, it is pertinent that we have an understanding of what causes landslides.
According to Newton's first law of motion,
> An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
This law literally means, that for every action, there is a cause. Landslides doesn't just happen on their own, they occur whenever a landslope becomes unstable. This instability is caused by natural events or man-made actions.
Under the natural events, events like the pressure of groundwater, earthquakes, volcanic eruption, the absence of soil nutrients vegetative and soil structure due to wildfire and erosion, causes the destabilization of slopes.
<div class="pull-right"><center><img src="https://peda.net/p/rixi.r-s/e5o/e5/6-vuosiluokka/mmor/maapallon-kerrokset/sj:file/download/f97f6ef06d3a33e2e69d27b41f672c7f9d09d4af/shutterstock_331872611_Ammit%20Jack_tulivuori_ecuador_p.jpg" /><br/><em><a href="https://peda.net/p/rixi.r-s/e5o/e5/6-vuosiluokka/mmor/maapallon-kerrokset/sj">peda.net: Volcanic eruptions are one of the causes of landslide</a></em></center></div>
Under human influenced factors, we have events like the vibration of machines, bomb detonations, deforestation, earthworks that changes the way a slope is shaped when uprooting vegetation with roots that are so deep into the soil and other agricultural activities that influences the amount of water entering into the soil. These factors causes instability in slopes, and the aftermath of this is a landslide.
**TYPES OF LANDSLIDES**
Remember that in the beginning we learnt that landslide is more of a general term. Right now, I would be listing out those different phenomenons that are generally referred to as landslides.
**Debris Flow**
Debris flow develops as a result of the slope material like mud and rocks (which has becomes saturated with water) flowing down and carrying along with it houses, trees, cars e.t.c. These houses, cars and trees causes blockage, blocking bridges and other things. As a result of the blockage, flooding occurs in the path of the movement of the flow.
Do not make a mistake of thinking that debris flow is the same as flash flood, they are not the same.
Debris flow can be quite dangerous, in it fury it causes severe damages to structures, bringing buildings to the ground and destroying lives in that area. Normally, it starts when shallow landslides blocks stream bed, when the bed can't hold it anymore, it explodes.
<div class="pull-left"><center><img src="https://lh4.googleusercontent.com/proxy/LgHUtQQpniyWKXdtRb0zYjMYnbNBy-gfp-G25Vnn7HyRur-02OBCrQgzDakq5qzLfnM1BJPZEQtvQsLdE5xnaG_snjygndgBsmyiMEXkaVmLppxXSNPc=w513-h286-nc" /><br/><em><a href="https://www.flickr.com/photos/jsjgeology/37537977946">flickr.com: The deposit after a debris flow.</a></em></center></div>
This single action creates a very large volume of mass which carries with it a very large amount of debris as it flows. Remember that what we have now is a mixture of solids and water, and due to the respective densities of the constituents of the debris flow, the mixture might have density that is up to 2000kg/m³, and due to the force acting on it, it might be flowing at the speed of 14m/s.
When this occurs, it causes road blocks as the debris it carries with it piles up, heaps upon heap. In some cases, due to the force of the debris, roads, bridges and even train tracks which are on its path of travel are destroyed completely.
**Shallow landslides**
This refers to a landslide that occurs in a sliding surface which is situated few depths inside the soil. Shallow landslides always occur in areas in which their slopes is such that it has high permeable soils on top with soil of low permeability beneath it. It is this bottom soil with low permeability that traps the water in the high permeable soils. This action creates a pressure in the top soil, which increases as the top soil gets filled with water. This continues till the slope becomes very unstable. At that point the top soil slide over the lower soil. A perfect instance of shallow landslide is noticed in slopes with silt and sand as the top soil and with bedrock as the lower permeable soil. When rain falls, the rain that sips through the sand and silt is been trapped by the bedrock till the top soil becomes too heavily saturated that it starts to slide over the bedrock.
**Earthflows**
Another type of landslide is the earthflow. Majorly, they are downslopes that consist of the flow, at any speed from 0.2km/h - 20km/h, of fine grained materials that are saturated. The rate of flow of earthflows are quite slower than that of mudflows. The materials it carries along with it as it travels includes fine sand, clay, pryoclastic materials and other particles with fine grains like silt. The velocity of flow of an earthflow is dependent solely on the amount of water it contains. Thus, if it contains a higher amount of water, it flows at a faster rate than when it contains lower amount of water.
[Picture by Jerrye and Roy Klotz MD - Wikicommons CC BY-SA 3.0
An earthflow](https://commons.m.wikimedia.org/wiki/File:SLUMGULLION_EARTHFLOW,_HINSDALE_COUNTY,M_COLORADO.jpg)
Before the flow starts fully, these fine grained masses experiences a pressure from those pores were the fluid comes out from, and as expected, they resist. This resistance reduces as the force of the water increases till a point is reached when the pore water is able to overcome the resistance and also be able to support lthe weight of the material. This action results to a bulging lobe which progresses with a slow but rolling motion. As it progresses, the lobes spreads out, the velocity of flow decreases due to the increase in the drainage of the mass. Even though, it reduces the speed of the flow, this process causes the flow to thicken, and that happening is bad news.
Earthflows occur mostly during periods of high rainfalls, and other precipitation that causes the saturation of the earth.
**Sturzstrom**
There is currently no much facts about this kind of landslide, all that is known about it is that even though it is very large, it flows to a very far distance. It doesn't necessarily need the land surface to be very steep, it can flow over flat surfaces, and even lands that has very low angle.
**Debris Slide**
This landslide is triggered when thick vegetated slopes gets saturated, thus the landslide always contains mixtures of timbers, vegetation and other debris. It has a distinctive attribute which can be noted by the random movement of rocks, debris which are mixed together with water or any other precipitate and soil.
**Note*:-
Do not confuse debris avalanches to be debris landslide, they are two different phenomenons. The debris avalanches moves at a more faster rate than landslide, and it usually occurs at a more steeper slope with high water content more the one found in debris landslide.
<div class="pull-right"><center><img src="https://upload.wikimedia.org/wikipedia/commons/3/3e/Goodell_Creek_Debris_Avalanche.jpg" /><br/><em><a href="https://commons.m.wikimedia.org/wiki/File:Goodell_Creek_Debris_Avalanche.jpg">Picture by G310Luke - wikicommon CC BY-SA 3.0
Debris Avalanche</a></em></center></div>
When debris slide starts, it first begins with big rocks falling from the top of the slide towards the bottom. These big rocks breaks into pieces as it falls, and it falls at a rate that is slower than the speed of a debris avalanche. As it moves down the slope it forms a channel that leaves a V-shaped mark as it flows down to the bottom of the hill.
**Deep-seated landslide**
Deep-seated landslides are those landslides that occurs in the sliding surfaces deep below the earth's surface, at depths more than 10m below. They move at very slow pace and they are more larger than shallow landslides and they can be identified by the concave scarps at the top and steep areas at the toe.
**EFFECTS OF A LANDSLIDES**
Apart from the death tolls it leaves on its path, and the destruction of property by covering the whole land with debris, whenever a landslide occurs, especially close to a sea and it prompts a rockfall or a volcanic eruption, it causes a great disturbance in the water high enough to cause a tsunami. The more serious the landslide is, the more destructive and higher the tsunami is. An example of a tsunami occurrence caused by a landslide is the tsunami that occurred in Lituya Bay in Alaska in 1958.
**RELATED PHENOMENON**
There are two events that look so much like a landslide but they are not. They are an avalanche, and a pyroclastic flow.
An avalanche still involves the sliding of a very large amount of ice, snow and rock down a mountain but unlike landslides, it does that at an incredible speed.
Another is the pyroclastic flow which involves the down flow of hot ash, gas and rocks down an erupting volcano after a volcanic eruption.
**SHAPING HISTORY**
Landslides have been of great influence in the way the earth is shaped, even the position of some mountains are as a result of landslides. An example is the landslide that occurred 48 million years ago, considered as the largest continental landslide in history, which caused the movement of the Heart mountain from its previous position to where it is now.
A lake in North Island of New Zealand called lake Waikeremoana was formed as a result of a landslide that occurred about 200BC.
<div class="pull-left"><center><img src="https://teara.govt.nz/files/p12996doc.jpg" /><br/><em><a href="https://teara.govt.nz/en/photograph/12996/lake-waikaremoana">teara.govt.nz: Lake Waikaremoana</a></em></center></div>
This landslide caused a huge rock to slide and dam a gorgeous of the Waikaretaheke river creating a hole with depth of about 256 meters.
Another notable occurrence is the landslide which reduced the size of a mountain about 60km north of Kathmandu. If that slide haven't occurred, that mountain would have been one of the mountains on earth with height of more that 8000m above the ground.
The Manang-Braga rock debris flow that occurred on the Marsyangdi Valley in the Annapurna Region of Nepal is another one. It was powerful enough to cross boundaries and it moved materials with a volume of more than 15000m³ over a great distance, just in one event.
The last landslide occurrence which shaped history that I would make mention of is the Storegga Slide that happened about 8000 years ago close to the west coast of Norway. Regarded as one of the largest in history, it caused a tsunami whose effect was felt by the countries close to the North Sea. The landslide and it's effect moved debris with volume of about 3,500,000m³ and size comparable to the whole of Iceland with a thickness of 34m.
**PREDICTION OF LANDSLIDE**
Since man is ever faced with the problem of landslide, it is really of man's best interest to discover a means knowing when a landslide is about to occur. Advancement in science and technology have really helped man to be able to predict a landslide before it occurs based on lessons learnt from previous occurrences. I will be discussing about few of these techniques in this article.
One of the techniques is conducting of landslide hazard analysis and mapping. This technique is quite useful since it goes a long way in providing the necessary information needed to forecast a landslide. With these informations we develop rules and regulations on how to make the best use of our lands so as to prevent landslide from occurring. Using this analysis, we can even establish a relation between the factors that causes landslides, their pre-warning signs and from these established relationship predict the occurrence of a landslide. The factors that we consider in these analysis are classified into geology, land use, hydrogeology and germorphology.
[Picture from Wikicommon CC BY-SA 3.0
The GIS (Geographical Information system)](https://commons.m.wikimedia.org/wiki/File:Gis.jpg)
One of the tools used in landslide analysis, mapping and prediction is the GIS which has the functions of collection of data, storing and manipulating of these data very fast and effectively. Another tool used in landslide hazard analysis is the remote sensing techniques. There is also the "before and after aerial photography" and the "satellite imagery" which helps us to study the changes that occur in a landscape after a landslide occurrence. It also goes further to reveal what causes landslide, if the area is in danger of a landslide occurrence and how the area recovers after the landslide has occurred.
Combining these two methods, the GIS and the satellite imagery, we can make predictions of high probability of the chances of a future landslide occurrence. These predictions are based on the assumption that the occurrence of a landslide is dependent on certain factors that are geological, and that future landslides are more likely to occur as a result of what caused the previous ones. Thus, with these two method we establish a relationship between the past and the future.
**MAN AND LANDSLIDE**
Try pronouncing "landslide", it's sounds cool, right? Well, don't let it deceive you, they are very very dangerous. Those that were lucky to survived a landslide described that they felt as if the world was crumbling around them when it was happening. I will be listing out few of the landslides that occurred in human history.
**[The North India Flood Mudslide of 2013](https://en.m.wikipedia.org/wiki/2013_North_India_floods)**
This is regarded as one of the worst disaster that have ever happened in the history of India. It occurred in June, 2013 in the Himalayan state of Uttarakhand, killing about 5,700 people. This mudslide was caused by a lot of factors, ranging from the incessant rainfall in that area to the unchecked tourism which increased the number of buildings and population in that area. You know how harmful over population is to the environment. Another factor is the mushrooming of the hydroelectric dams in that area. Since the dams were too small, in addition to the excessive rainfalls with no outlet for them, flooding was inevitable. When the flooding finally prompted the landslide, it carried with it muds and rocks, releasing it's fury on the towns, villages and the people around as it buried all of them alive.
** [The Vargas Tragedy of 1999](https://en.m.wikipedia.org/wiki/Vargas_tragedy)**
Till today, the winter of 1999 is regarded as one of the worst periods in the history of the Vargas State of Venezuela.
<div class="pull-right"><center><img src="https://upload.wikimedia.org/wikipedia/commons/1/1d/Caraballeda_1999_Deposits_and_Damage.jpg" /><br/><em><a href="https://commons.m.wikimedia.org/wiki/File:Caraballeda_1999_Deposits_and_Damage.jpg">Picture by Smith, Lawson, US ACE, Wikicommon CC BY-SA 3.0
The aftermath of the Vargas landslide</a></em></center></div>
The excessive rainfall that occurred in those period caused a series of flash floods and debris flows which claimed the lives of more than 30,000 people (about 10% of Vargas population) living in that area. The landslide was very powerful, it covered the entire towns of Carmen de Uriah and Cerro Grande with mud up to the extent that the peak of a house can't be seen. Others that weren't covered by the mud bed were swept away into the ocean nearby by the flood.
**[Haiyuan Flows of December, 1920](https://en.m.wikipedia.org/wiki/1920_Haiyuan_earthquake)**
The second deadliest earthquake of the 20th century which happened in Haiyuan prompted up to 675 major landslides. These landslides caused massive destruction of both lives and properties. Among these 675 landslides, the landslide that occurred in December 16th of that year claimed the lives of over 100,000 people while at the same time causing serious havoc across the surrounding, with an area of about 20,000km². Another of the landslide that occurred also in that period buried the entire village of Xiji County.
**[The Nevado Huascaran debris falls of 1970](https://www.climate-policy-watcher.org/plate-tectonics/landslides-in-the-andes-mountains-nevados-huascaran-peru-1962-1970.html)**
The last but not the least is the Nevado Huascaran debris falls that occurred in May 1970. These landslides were triggered by an earthquake. It was terrible, the landslide and avalanche caused havoc over a distance of 16.5km, covering the whole towns of Yungay and Ranrahirca with rocks, mud, water and snow, stealing the lives of everything living thing covered by it.
**INDICATORS OF A LANDSLIDE OCCURRENCE**
Always be conscious of your surrounding, if you notice changes in your landscape and patterns that appear like storn-water drainage on slopes, or you observe unnecessarily land movement and flows or all the trees within your habitat and even the electric poles appearing to be leaning, there is a chance of a landslide occurrence.
Other signs includes new cracks appearing in foundations, tiles, plasters and bricks, or a long crack on the road. You may also notice the outside wall or stairs beginning to pull itself out of the building. Sometimes a bulging ground appears close to the bottom of the slope.
Other signs includes the unusual noise that indicates boulders colliding to gather as the debris flows, the faint sound that announces landslides as it approaches, water coming out the ground in several locations, sudden collapse of pavements, fallen rocks on the road sides e.t.c.
Whenever you notice any of these signs, be prepared.
**HOW TO SURVIVE A LANDSLIDE**
**What to do before a landslide**
You need to know this so as know how to save yourself and your family if a landslide happens to occur.
The first thing to do is to always have an emergency kit in case there is a needed for immediate evacuation. Make a plan with your family on how to contact each other, incase the landslide happens to separate the family.
Do not build a house close to a steep slope or a mountain edge, a valley or any land that is suceptible to a landslide, always keep your distance away from them. Study your environment, know if there have been a landslide occurrence there before, this is because a landslide is more likely to occur where it has happened before.
<div class="pull-left"><center><img src="http://s0.geograph.org.uk/photos/10/33/103396_9d0eefbf.jpg" /><br/><em><a href="http://www.geograph.org.uk/photo/103396">geograph.org.uk: A valley</a></em></center></div>
Surround your house with a building retaining wall that can help guide the flow away from your house. It can help protect your house in case a landslide is to occur. Use a flexible pipes which can withstand breakage in making connections in your house.
Insure your house with flood insurance policies. Take an account of your property and their worth, take pictures for proof.
**What to do during a landslide**
Always be awake an alert during severe storms, most people have been killed while they slept by a landslide because they felt the storm was just normal.
Don't spend all your time watching movies, always listen to the news so as to be forewarned of landslide before it reaches your location, and be ready to leave at a moment notice.
Once you notice an unnecessary sound, be alert so as to be sure it is not the sound of a debris movement that you have just heard. If it is, get yourself far away from the path of the landslide with all immediate effect and as fast as you can.
Always be mindful that landslides can move faster than you can run, and it's speed intensifies when it gets close to or powered by a near stream, or if the rain fell recently. So, while running make sure you look upstream and that no mudflow is approaching before you cross any bridge or road. And make sure you avoid low lying areas while running.
Incase you can't escape from the mudflow or landslide, curl yourself into a tight ball, and protect your head while you do that.
[Picture from Wikicommon CC BY-SA 3.0
Aftermath of a landslide on the Cairns Railway](https://commons.m.wikimedia.org/wiki/File:StateLibQld_1_150427_Aftermath_of_a_landslide_on_the_Cairns_Railway,_Cairns_Range,_1911.jpg)
**What to do after a landslide**
Do not come back to your home yet, in fact stay away from the area the slide occurred, there are high chances of another landslide to occur within minutes after the first.
Listen to the news, when the local authorities says its safe to go home, only then should you go back. Remember that sometimes flooding occurs after a landslide.
Check out for those who survived the landslide, direct rescuers to their location. Also help in taking care of the wounded.
Watch your steps, be careful not to step on a utility wire they might still have electricity in them, to avoid being electrocuted. Report damaged road, railways and broken utilities lines to the right authorities so that something would be done about it.
If the house was destroyed by the landslide, take a photograph of the destruction, you might need it to collect your insurance benefits.
If the house is still standing, check the foundation of the building and be sure that it can still carry the building. Also check out the surrounding land to know the extent of the damage.
Make some repairs, and also cover up the areas that were eroded to avoid flash flooding or any future landslide. Consult a geotechnical expert so as to be educated on what to do to avoid any future landslide.
**MY THOUGHTS**
##### A study of natural disasters shows how man is in strong conflict with its environment. It seems as if the environment retaliates to whatever man does to it. Sadly, landslide is one of those ways nature retailates. There are two main causes of landslide one of them being human action. When man pulls out a tree that has root that goes very deep into the soil, it affects the structure of the earth. Nature itself in one of its modes of retaliation develops a slide which leaves a lot of people dead.
##### I recently shared my thoughts of how man is causing so much harm to nature and how heavily man has payed the price for doing, with a course mate. Well, he didn't agree with my school of thought. His arguement was that for man to advance, he needs to try out new things and whatever sacrifices had to be made to achieve that, it should be made. You can see how foolish education have made some of us. The best and the first thing for man to do in other to prevent himself from being killed by any natural disaster is to discover a means of advancing without destroying our earth, I think we have sacrificed enough. Don't you think so too? Putting an end to all human actions that causes landslides or other factors that causes landslides (e. g tsunami and earthquake), it would go a long way in putting an end to landslide.
##### The last time I was with Steve, one of my friends, we tried to come up with a shelter that can protect man from all natural disaster, since man thinks it's best for him to be in the defensive. We discovered that what man needs is just a "turtle shell" that can withstand a full force of more than 5000N without collapsing. Instead of using the foundation of a two storey building to construct a three storey in the name of saving resources, why don't man think more to the future by building a two storey building using a three storey building and see if it won't stand a landslide. Also houses should be built in such a way that it's center gravity is positioned very close to the earth so as to withstand any force, be it air, water or rocks. I believe man can balance advancement with protection of earth, only if he allows his mind to explore so many possibilities.
**REFERENCES**
[What is a landslide](http://www.ga.gov.au/scientific-topics/hazards/landslide)
[Causes of landslides](https://www.usgs.gov/faqs/what-a-landslide-and-what-causes-one?qt-news_science_products=7#qt-news_science_products)
[Landslide Wpedia](https://en.m.wikipedia.org/wiki/Landslide)
[What to do during a landslide](https://www.ready.gov/landslides-debris-flow)
[The GIS](https://en.m.wikipedia.org/wiki/Geographic_information_system)
[Newton's first law](http://www.physicsclassroom.com/class/newtlaws/Lesson-1/Newton-s-First-Law)
[Deadliest landslides in human history](https://www.worldatlas.com/articles/deadliest-landslides-in-recorded-history.html)
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