Quick clay
Encyclopedia
Quick clay, also known as Leda clay and Champlain Sea clay in Canada
, is a unique form of highly sensitive marine clay
, with the tendency to change from a relatively stiff condition to a liquid mass when it is disturbed. Undisturbed quick clay resembles a water-saturated gel
. When a mass of quick clay undergoes sufficient stress, however, it instantly turns into a flowing ooze, a process known as liquefaction
. A small block of quick clay can liquefy from a stress as simple as a modest blow from a human hand, while a larger deposit is mainly vulnerable to greater stresses such as earthquake
vibrations or saturation by excess rainwater. Quick clay behaves this way because, although it is solid, it has a very high water content, up to 80%. The clay retains a solid structure despite the high water content, because surface tension
holds water-coated flocs
of clay together in a delicate structure. When the structure is broken by a shock, it reverts to a fluid state.
Quick clay is only found in the northern countries such as Russia
, Canada
, Norway
, Sweden
, and Finland
, and in the US
state of Alaska
, which were glaciated during the Pleistocene epoch. In Canada, the clay is associated primarily with the Pleistocene-era Champlain Sea
, in the modern Ottawa Valley
, St. Lawrence Valley and Saguenay River
regions.
Quick clay has been the underlying cause of many deadly landslide
s. In Canada alone, it has been associated with more than 250 mapped landslides. Some of these are ancient, and may have been triggered by earthquakes.
). All of the ground-up rock was deposited in the surrounding ocean, which had penetrated significantly inland. The loose deposition of the silt and clay particles in the marine environment, allowed an unusual flocculation
to take place. Essentially, this formed a strongly bonded soil skeleton, which was 'glued' by highly mobile sea-salt ions.
At this point, there was only the formation of very strong marine clay
, which is found all over the world and highly stable, but with its own unique geotechnical problems. When the glaciers retreated, the land mass rose (post-glacial rebound
), the clay was exposed, and formed the soil mass for new vegetation. The rainwater in these northern countries was quite aggressive to these clays, perhaps because it was softer (containing less calcium), or the higher silt content allowed more rainwater and snowmelt to penetrate. The final result was that the ionic 'glue' of the clay was weakened, to give a weak, loose soil skeleton, enclosing significant amounts of water (high sensitivity with high moisture content).
Quick clay deposits are rarely located directly at the ground surface, but are typically covered by a normal layer of topsoil. While this topsoil can absorb most normal stresses, such as normal rainfall or a modest earth tremor, a shock that exceeds the capacity of the topsoil layer — such as a larger earthquake, or an abnormal rainfall which leaves the topsoil fully saturated so that additional water has nowhere to run off
except into the clay — can disturb the clay and initiate the process of liquefaction.
These landslides are retrogressive
, meaning they usually start at a river, and progress upwards at slow walking speed. They have been known to penetrate kilometers inland, and consume everything in their path.
In modern times, areas known to have quick clay deposits are commonly tested in advance of any major human development. It is not always possible to entirely avoid building on a quick clay site, although modern engineering techniques have found technical precautions which can be taken to mitigate the risk of disaster. For example, when Ontario
's Highway 416
had to pass through a quick clay deposit near Kemptville
, lighter fill materials such as polystyrene
were used for the road bed, vertical wick drains were inserted along the route and groundwater
cutoff walls were built under the highway to limit water runoff into the clay.
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, is a unique form of highly sensitive marine clay
Marine clay
Marine clay is a type of clay found in coastal regions around the world. In the northern, deglaciated regions, it can sometimes be quick clay, which is notorious for being involved in landslides....
, with the tendency to change from a relatively stiff condition to a liquid mass when it is disturbed. Undisturbed quick clay resembles a water-saturated gel
Gel
A gel is a solid, jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state...
. When a mass of quick clay undergoes sufficient stress, however, it instantly turns into a flowing ooze, a process known as liquefaction
Soil liquefaction
Soil liquefaction describes a phenomenon whereby a saturated soil substantially loses strength and stiffness in response to an applied stress, usually earthquake shaking or other sudden change in stress condition, causing it to behave like a liquid....
. A small block of quick clay can liquefy from a stress as simple as a modest blow from a human hand, while a larger deposit is mainly vulnerable to greater stresses such as earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
vibrations or saturation by excess rainwater. Quick clay behaves this way because, although it is solid, it has a very high water content, up to 80%. The clay retains a solid structure despite the high water content, because surface tension
Surface tension
Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...
holds water-coated flocs
Flocculation
Flocculation, in the field of chemistry, is a process wherein colloids come out of suspension in the form of floc or flakes by the addition of a clarifying agent. The action differs from precipitation in that, prior to flocculation, colloids are merely suspended in a liquid and not actually...
of clay together in a delicate structure. When the structure is broken by a shock, it reverts to a fluid state.
Quick clay is only found in the northern countries such as Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
, Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
, and Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...
, and in the US
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
state of Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
, which were glaciated during the Pleistocene epoch. In Canada, the clay is associated primarily with the Pleistocene-era Champlain Sea
Champlain Sea
The Champlain Sea was a temporary inlet of the Atlantic Ocean, a paratropical subsea or epeiric sea created by the retreating glaciers during the close of the last ice age...
, in the modern Ottawa Valley
Ottawa Valley
The Ottawa Valley is the valley along the boundary between Eastern Ontario and Western Quebec along the Ottawa River. The valley is the transition between the Saint Lawrence Lowlands and the Canadian Shield...
, St. Lawrence Valley and Saguenay River
Saguenay River
The Saguenay River is a major river of Quebec, Canada.It drains Lac Saint-Jean in the Laurentian Highlands, leaving at Alma and running east, and passes the city of Saguenay. It drains into the Saint Lawrence River at Tadoussac....
regions.
Quick clay has been the underlying cause of many deadly landslide
Landslide
A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...
s. In Canada alone, it has been associated with more than 250 mapped landslides. Some of these are ancient, and may have been triggered by earthquakes.
Formation of quick clay
At the height of the past glaciation (about 10,000 years ago), the land was 'pushed' down by the weight of the ice (isostatic depressionIsostatic depression
Isostatic Depression is the term used by geologists for the sinking of large parts of the Earth's crust into the asthenosphere. The sinking is caused by a heavy weight placed on the Earth's surface...
). All of the ground-up rock was deposited in the surrounding ocean, which had penetrated significantly inland. The loose deposition of the silt and clay particles in the marine environment, allowed an unusual flocculation
Flocculation
Flocculation, in the field of chemistry, is a process wherein colloids come out of suspension in the form of floc or flakes by the addition of a clarifying agent. The action differs from precipitation in that, prior to flocculation, colloids are merely suspended in a liquid and not actually...
to take place. Essentially, this formed a strongly bonded soil skeleton, which was 'glued' by highly mobile sea-salt ions.
At this point, there was only the formation of very strong marine clay
Marine clay
Marine clay is a type of clay found in coastal regions around the world. In the northern, deglaciated regions, it can sometimes be quick clay, which is notorious for being involved in landslides....
, which is found all over the world and highly stable, but with its own unique geotechnical problems. When the glaciers retreated, the land mass rose (post-glacial rebound
Post-glacial rebound
Post-glacial rebound is the rise of land masses that were depressed by the huge weight of ice sheets during the last glacial period, through a process known as isostasy...
), the clay was exposed, and formed the soil mass for new vegetation. The rainwater in these northern countries was quite aggressive to these clays, perhaps because it was softer (containing less calcium), or the higher silt content allowed more rainwater and snowmelt to penetrate. The final result was that the ionic 'glue' of the clay was weakened, to give a weak, loose soil skeleton, enclosing significant amounts of water (high sensitivity with high moisture content).
Quick clay deposits are rarely located directly at the ground surface, but are typically covered by a normal layer of topsoil. While this topsoil can absorb most normal stresses, such as normal rainfall or a modest earth tremor, a shock that exceeds the capacity of the topsoil layer — such as a larger earthquake, or an abnormal rainfall which leaves the topsoil fully saturated so that additional water has nowhere to run off
Surface runoff
Surface runoff is the water flow that occurs when soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land. This is a major component of the water cycle. Runoff that occurs on surfaces before reaching a channel is also called a nonpoint source...
except into the clay — can disturb the clay and initiate the process of liquefaction.
Potential disaster
Because the clay layer is typically covered with topsoil, a location which is vulnerable to a quick clay landslide is usually identifiable only by soil testing, and is rarely obvious to a casual observer. Thus human settlements and transportation links have often been built on or near clay deposits, resulting in a number of notable catastrophes:- On 19th May 1893, a landslide in Verdal, Norway, killed 116 people and destroyed 105 farms. It left a crater several kilometers in diameter.
- The most disastrous such landslide to affect North America occurred in 1908, when a slide into the frozen Du Lièvre RiverDu Lièvre RiverThe du Lièvre River is a river in western Quebec which flows south from the Mitchinamécus reservoir and empties into the Ottawa River at Masson-Angers. The river is 330 km in length and drains an area of 10,400 km²...
propelled a wave of ice-filled water into Notre-Dame-de-la-SaletteNotre-Dame-de-la-Salette, QuebecNotre-Dame-de-la-Salette is a village and municipality in the Outaouais region of Quebec, Canada. It is part of the Les Collines-de-l'Outaouais Regional County Municipality, straddling the eastern banks of the Du Lièvre River.-History:...
, QuebecQuebecQuebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....
causing the loss of 33 lives and the destruction of 12 homes.
- In 1955, a landslide affected part of the downtown of NicoletNicolet, QuebecNicolet, Quebec is the county seat of Nicolet-Yamaska Regional County Municipality, Quebec, Canada. The population as of the Canada 2006 Census was 7,827...
, Quebec, causing $10 million in damages.
- On May 4, 1971, 31 lives were lost when 40 homes were swallowed up in a retrogressive flowslide in Saint-Jean-Vianney, QuebecSaint-Jean-Vianney, QuebecSaint-Jean-Vianney was a village in the Saguenay-Lac-Saint-Jean region of Quebec, which was abandoned after it was partially destroyed in a landslide on May 4, 1971.-History:...
, resulting in the relocation of the entire town when the government declared the area uninhabitable due to the presence of Leda clay.
- The experience of Saint-Jean-Vianney contributed to the abandonment of the town of Lemieux, OntarioLemieux, OntarioLemieux is a ghost town in the Canadian province of Ontario, which was located on the shore of the South Nation River in the Prescott and Russell County township of South Plantagenet...
in 1991, after a 1989 study showed it was also located on the same type of clay along the South Nation RiverSouth Nation RiverThe South Nation River is a river in Eastern Ontario, Canada. It springs from forests and marshes located north of Brockville and it flows 175 km northeast to empty into the Ottawa River north of Plantagenet...
. In 1993, those findings were borne out when town's abandoned main street was swallowed by a massive 17 hectareHectareThe hectare is a metric unit of area defined as 10,000 square metres , and primarily used in the measurement of land. In 1795, when the metric system was introduced, the are was defined as being 100 square metres and the hectare was thus 100 ares or 1/100 km2...
landslide.
- Another famous flow of quick clay at Rissa, NorwayRissa, NorwayRissa is a municipality in Sør-Trøndelag county, Norway. It is part of the Fosen region. The administrative centre of the municipality is the village of Årnset...
, in 1978 caused about 33 hectares (82 acres) of farmland to liquefy and flow into the lake Botn over a few hours, with the loss of one life. The Rissa slide was well recorded by local citizens and a documentary film was made about it in 1981.
- On May 11, 2010, quick clay took the lives of a family living in Saint-JudeSaint-Jude, QuebecSaint-Jude is a municipality in southwestern Quebec, Canada in the Regional County Municipality of Les Maskoutains. The population as of the Canada 2006 Census was 1,130.-Population:Population trend-Language:Mother tongue language ...
, QuebecQuebecQuebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....
, when the land their house was built on suddenly tumbled down toward the Salvail River. The landslide was so sudden that the family members died where they sat; they had been watching an ice hockey game on television.
These landslides are retrogressive
Headward erosion
Headward erosion is a fluvial process of erosion that lengthens a stream, a valley or a gully at its head and also enlarges its drainage basin. The stream erodes away at the rock and soil at its headwaters in the opposite direction that it flows. Once a stream has begun to cut back, the erosion is...
, meaning they usually start at a river, and progress upwards at slow walking speed. They have been known to penetrate kilometers inland, and consume everything in their path.
In modern times, areas known to have quick clay deposits are commonly tested in advance of any major human development. It is not always possible to entirely avoid building on a quick clay site, although modern engineering techniques have found technical precautions which can be taken to mitigate the risk of disaster. For example, when Ontario
Ontario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....
's Highway 416
Highway 416 (Ontario)
King's Highway 416, commonly referred to as Highway 416 and as the Veterans Memorial Highway, is a 400-series highway in the Canadian province of Ontario which connects Highway 417 in Ottawa with Highway 401 between Brockville and Cornwall...
had to pass through a quick clay deposit near Kemptville
Kemptville, Ontario
Kemptville is a community located in the Municipality of North Grenville in Southern Ontario, Canada in the northernmost part of the United Counties of Leeds and Grenville...
, lighter fill materials such as polystyrene
Polystyrene
Polystyrene ) also known as Thermocole, abbreviated following ISO Standard PS, is an aromatic polymer made from the monomer styrene, a liquid hydrocarbon that is manufactured from petroleum by the chemical industry...
were used for the road bed, vertical wick drains were inserted along the route and groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
cutoff walls were built under the highway to limit water runoff into the clay.
External links
- Quick clay in Sweden, by the Geotechnical Institute of Sweden
- Rissa Landslide, by University of Washington: short synopsis with link to video clips
- Geoscapes Ottawa-Gatineau: Landslides, by Natural Resources Canada: Leda clay landslides in the lower Ottawa River Valley