Quick clay

Quick clay, also known as Leda clay and Champlain Sea clay in Canada, is a special kind of very sensitive glaciomarine clay found in many places around the world, including Canada, Norway, Russia, Sweden, Finland, and the United States. This clay is special because it can change shape very easily. When it gets stressed or shaken, like during an earthquake or after a lot of rainfalls, the clay can suddenly turn from a solid-like material into a flowing liquid.

This sudden change can cause big problems, leading to landslides. The ground can move quickly and unexpectedly, making it dangerous for people and buildings nearby. The change happens because of something called soil liquefaction, which is when the soil loses its strength and behaves more like water. Small vibrations can trigger this process, turning solid ground into a slippery, flowing mass.

Quick clay is important to study because it helps scientists and engineers understand how to build safer structures in areas where this clay is found. Knowing how quick clay behaves helps people prepare for and prevent dangerous landslides, protecting lives and property.

Quick clay main deposits

Quick clay is found in countries near the North Pole, like Russia, Canada, Norway, Sweden, Finland, and Alaska in the United States. These places were covered by ice during an ancient time called the Pleistocene epoch. In Canada, quick clay is linked to the old Champlain Sea and is common around the Ottawa Valley, the St. Lawrence Valley, and the Saguenay River areas.

This special kind of clay can cause landslides when it suddenly turns from solid to liquid after being disturbed. In Canada alone, quick clay has been linked to over 250 landslides, some of which might have started because of earthquakes.

Clay colloids stability

Quick clay is very unstable because its particles can change from a solid to a watery state when disturbed. This happens because clay particles have a negative charge and are surrounded by a layer of water molecules. In salty water, these particles stick together, but when the water becomes fresh, they spread apart, making the clay weak and unstable.

When quick clay is disturbed, like during an earthquake or heavy rain, it can lose its strength and flow like water. Adding salt can help it regain its strength by bringing the particles back together.

Formation of quick clay

Long ago, during the last ice age about 20,000 years ago, huge glaciers pushed down on the land. This caused rocks and dirt to be carried into the ocean, which had moved far inland. In this ocean water, tiny particles of silt and clay formed a special kind of soil that stayed strong because of salt ions in the water.

When the glaciers melted, the land rose up again, and this clay was left behind. Rainwater, which was low in certain minerals, weakened the clay over time. This made the clay loose and filled it with water. Usually, a layer of topsoil protects this weak clay. However, big events like strong earthquakes or heavy rain can soak through the topsoil and cause the clay to suddenly turn watery and flow like a liquid.

Main article: Flocculation
Main articles: Marine clay · Post-glacial rebound