Landslides around the world

Highway 64 rock slide Tennessee, 2009

On 10 November 2009, a local news crew were at a road-side site investigating a previous rock slide.

Strange popping sounds on the cliff face were heard as small fragments of rock started to bounce down the slope.

Luckily, there was a geologist on site, who recognised this as a sign that another landslide might happen, and she moved everybody out of the way.

The camera man just stood with his camera and recorded this amazing footage of a rock slide event.

This rock is made up of thin layers that dip towards the road that has cut through this mountain side. As water seeps through weak spots (bedding or cleavage planes), the rock loses strength and the rocks slide.

Maiereto landslide Italy, Calabria, 2010

On 15 Feb 2010, the side of a hillslope slipped past people whilst they stood and watched.

A landslide had happened here before and geologists had seen signs that it would move again so people were evacuated and no one was hurt.

Gravity constantly tugs downward on a slope, but only when gravity's force exceeds the strength of the rocks, soils, and sediments making up the slope does land begin to slide down hill.

Heavy rainfall in the Maierato region is likely to have started this slide.

Po Shan Road landslide, Hong Kong, 1972

On 18 June 1972, near 14 Po Shan Road approximately 40 000 m3 of debris travelled some 270 m down slope and resulted in 67 deaths, 20 injuries, two buildings destroyed and one building severely damaged.

A construction site above the major part of the landslide was being redeveloped at the time of the landslide.

In late 1971 two landslides had occurred at the site.

This landslide occurred over a few days.

  • 16 June 1972 cracks were noted
  • 17 June 1972 a small slip occurred above the construction site.
  • 18 June 1972 a major landslide travelled 270m down the slope
  • 19 June 1972 another small failure occurred
  • 20 June 1972 another small failure occurred.

Work on the construction site above the road, together with the exceptionally heavy rainfall in early 1972, caused this landslide.

About 1400 mm of rainfall was recorded between May and June 1972 and in particular more than 650 mm of rainfall was recorded from 16 to 18 June 1972 when the main landslide happened.

Quick clay landslide in Rissa, Norway, 1978

On 29 April 1978 a landslide wiped away an area of 330 km2 (about the same as 47 football pitches) including 13 farms, two homes and the local community centre.

The slide contained about 5 to 6 million m3 of material — about 2400 Olympic swimming pools — and was the biggest slide in Norway in this century. Of the 40 people caught in the slide area, only one person died.

In this case the farmer dug a pit on his land and put the extra material on the edge of the lake. This extra weight was too much for the clay to cope with and so the landslide began.

The slide started at the lake shoreline and developed backwards and landwards taking with it people, farms and homes.

This type of landslide is rare and was caused by the special make-up of the clay material.

Quick clay was laid down millions of years ago under the sea. Over the years, salt has been removed by water passing through it over time, leaving a clay crust with the salt-free marine clay underlying it.

When the clay has too much weight loaded on to it the strength fails, and collapses. It then becomes 'remoulded' and acts like a liquid.

Not only did the landslide travel backwards from the lake, it also caused great damage to the community of Leira when as a result of the clay sliding into the lake, a three-metre high floodwave reached the opposite bank of Lake Botnen shortly after the main slide.

Saidmareh landslide, West Iran

This is a huge landslide is thought to have occurred in prehistoric times, perhaps 10 300 years ago; an earthquake is the likely cause of this landslide.

It is a good example of how a landslide can be studied and mapped through modern satellite imagery.

It is known as the Saidmareh Landslide but is also sometimes called the Said Marreh, Seymareh or the Kubi Kuh Landslide.

It is 5 km wide and the landslide material covered an area of 64 square miles (165 km2). It is thought that 20 km3 of material was moved 50 billion tonnes of rock were moved in a single event — or enough water to fill eight million Olympic swimming pools!

The landslide blocked and dammed two rivers which meant that a pair of lakes formed. These have since drained leaving good soil for farming. The modern river has found a new channel through the landslide deposit.

The landslide carried rocks a long way and large blocks of rock have been found as far as nine miles (14 km) from their starting point.

The type of deposit left after the landslide occurred and the long distance these blocks travelled suggests that this was a landslide that happened at high speed also known as a rock avalanche or sturztrom.