The 1970 Ancash Earthquake

Podcast Transcript

On May 31, 1970, one of the most devastating disasters in Peruvian history occurred.

A magnitude 7.9 earthquake hit just off the coast of Peru, creating the most catastrophic natural disaster in the country’s history.

The “Ancash” or “Great Peruvian Earthquake” not only caused a disastrous loss of life but also had long-term impacts that shaped Peru for years to come.

It also showed, perhaps more than any other earthquake, it isn’t how much the ground moves, but also what it moves.

Learn about the Ancash Earthquake and its devastating impact on this episode of Everything Everywhere Daily.

Before getting into the details of the Ancash Earthquake, I would like to explain the geological conditions that makes Peru more susceptible to earthquakes when compared to other countries.

Peru is located on the Pacific Ring of Fire. The Ring of Fire received its name for holding roughly two-thirds of the world’s active volcanoes and the Earth’s greatest concentration of earthquakes.

The volcanoes are located on tectonic boundaries where two or more tectonic plates move against each other. If you recall my episode on volcanoes, these plates can rub against each other or be subducted below another plate. These plate boundaries can result in islands, mountains, volcanoes, and deep ocean ridges.

A common side effect of the movement of these tectonic plates is earthquakes.

Earthquakes are a result of sudden movements along geological faults. This sudden shift releases energy as a seismic wave, which makes the ground shake.

Peru sits right on the fault line of the Nazca plate and the South American plate.

The Nazca plate is oceanic, meaning its crust is more dense and therefore subducting underneath the less dense continental crust of the South American Plate.

The tectonic activity of the Nazca and South American plates causes the South American plate to essentially be pushed upward and fold in on itself, creating the Andes Mountains, which is the range Peru sits on.

The friction around the two plates leads to intense earthquake activity occurring in Peru, especially in the Western part of the country.

This means that many Peruvians are in areas that are more prone to natural disasters, including earthquakes, tsunamis, mudslides, and avalanches.

With that, on to the subject of this episode.

The Ancash or Great Peruvian Earthquake hit on May 31, 1970, at approximately 3:23 pm Peruvian Time, with the magnitude being reported as a 7.9 on the Richter scale.

7.9 is considered to be a major earthquake, but far from the largest.

The earthquake occurred roughly 25 kilometers off the coast of the Peruvian city of Chimbote.

Eyewitness accounts stated that “the Earthquake began without prior warning as a gentle swaying motion that lasted for a few seconds and was followed by hard shaking…estimated as lasting from 30 to 90 seconds.”

This earthquake impacted an area of roughly 83,000 km². To put that number in perspective, it would be larger than the combined area of Belgium and the Netherlands.

The effects on the area were devastating, especially to the Ancash and La Libertad Regions of the country.

The most shocking impact was on the town of Yungay.

Yungay was located in the Callejón de Huaylas valley of Peru, which is right between the Pacific Ocean and the Andes Mountain Range. The town was about 450 kilometers North of Lima and was surrounded by the Cordillera Blanca mountain range.

When the earthquake occurred, Huascaràn Mountain, the highest point in Peru and part of the Cordillera Blanca mountain range, had a massive glacier and a large amount of snowmass that became destabilized.

What followed was the glacier and snow rapidly surging downward, and turning to mud, while picking up large amounts of loose dirt, water, and rocks. This created a massive avalanche.

When the earthquake initially hit Yungay, many residents of the city flocked to churches to pray during the disaster.

The initial earthquake had already destroyed a good portion of the town’s buildings. However, if that were all that happened, I wouldn’t be doing an episode on it over 50 years later.

What came next would be far more devastating, making the disaster one that would be remembered.

Yungay was first hit with a large blast of air from the onrushing flow of material rushing down the mountain. It was followed by debris and boulders before the main semi-liquid wave arrived.

The mudflow that was triggered by the avalanche sped into the city at an estimated speed of 280 miles per hour or 335 kilometers per hour, instantly killing thousands of people.

The exact number of people killed in Yungay varies based on source, but roughly fifteen to twenty thousand people in Yungay died that day, leaving only 400 alive from the city of Yungay proper.

Of the survivors, roughly 300 were children who were attending a circus in a local stadium. A clown had led the children out of the stadium and on top of a hill in a nearby cemetery.

The surrounding villages near Yungay met a similar fate, bringing the death toll to 30,000 people.

It was the deadliest avalanche in world history by a wide margin, and would’ve been the deadliest natural disaster for the country since 1900 on its own.

Survivors of the Yungay disaster were moved to a refugee camp, which became known as “Yungay Norte.” The city would eventually be relocated and rebuilt, with the original Yungay’s location being declared a national cemetery.

However, Yungay was not the only city affected as the Earthquake impacted many other areas of Peru.

Many of the coastal cities in the Ancash region, including Chimbote, Recuay, and Carhuaz, had between 80 and 90% of their buildings completely destroyed.

These cities were hit so hard because of their poor physical infrastructure.

For example, the city of Chimbote had been a boomtown, growing from 1500 people in 1950 to 134,000 people in 1970.

This meant that a good portion of the city lived in “shanty towns.” These shanty towns were informal settlements with no access to things like sewage systems, electricity, or paved roads.

Many of these buildings were made of mud-dried bricks, and immediately collapsed when the earthquake hit.

Other cities in Peru that were impacted had similar shanty towns set up, which is why the infrastructural damage was so drastic in these cities.

All in all, an estimated 66,000 people lost their lives between the earthquake and the avalanche, making the disaster the deadliest in the history of Peru.

The rebuilding of the country would prove to be difficult.

On top of destroying infrastructure, killing thousands of people, and injuring countless more, the earthquake made rescue operations and aid distribution incredibly difficult.

As many impacted cities and towns were located within the Andes Mountains, the ability for aid to reach the area was exceptionally hard due to a large portion of the ground access into the mountains being completely blocked by the avalanche.

The problem was worsened by the dust in the air, making it difficult to conduct aerial reconnaissance in impacted areas.

Transporting necessary resources like food was also difficult for the government, as many of the roads were destroyed by the earthquake. This meant getting those resources to affected areas, including those on the coast, was a massive problem.

Providing shelter would also prove to be difficult for the government, as basically everything was destroyed. Many people were forced to sleep in military tents, refugee colonies, or amidst the rubble.

The damage caused by the earthquake was over $530 million US dollars which is equivalent to roughly $4.4 billion today, with emergency relief or aid being sent to Peru by 60 countries.

The aid helped ease conditions on the ground, but the earthquake exposed some of the fundamental problems within Peru.

Just two years before the earthquake occurred, Peru had a military coup. This resulted in the country being disorganized, which itself is an issue, but was exposed by the earthquake.

After the Ancash Earthquake, the Peruvian government rightfully wanted to make sure a disaster of that level would never occur again, so they enacted a series of policy reforms. However, many of these policies were widely unpopular or backfired.

This can be best illustrated by what happened in the town of Chimbote.

To create the best plan possible, Peru brought in geological experts from Japan and France. When testing the soil around Chimbote, they found that the soil was simply too unstable to settle on.

This led the government to conclude that the best way to prevent a future disaster would be to relocate the city center. This would put the city center further south on more stable land, which was already owned by the state.

This meant that the government could redistribute the land without bothering pre-existing landholders.

While this sounded great in theory, in practice, this would involve relocating a quarter of a million people. Many of these people did not want to have to travel further for work, lose their neighborhoods, and rebuild their homes.

Because of the massive public backlash, the government never enacted the plan and had to find another solution.

The new plan was to give a large number of citizens within shantytowns property titles, prioritizing those with kids. The goal of this initiative was to provide stability, particularly to family units, in the area. With the stability of owning land, the government hoped that the citizens would rebuild their homes with better materials.

Unfortunately for the government, this plan also backfired. Despite the rebuilding effort, Chimbote was still a boomtown, and its population continued to skyrocket, growing at the same rate as before the earthquake. This meant 75% of the people still lived in shanty towns.

A large reason why this backfired was the land reform itself. By giving out property, it incentivised people to stay or come to Chimbote. For many, the security of land was better than moving to an unknown area in a new city.

Another issue the government faced was the disruption to the economy.

In many of the impacted cities, the government faced a massive unemployment problem, and it was unable to supply new jobs. About 50% of the labor force was unemployed, leaving many Peruvians frustrated with the government.

Additionally, much of the foreign aid being provided went into fixing Peruvian industries rather than supporting the displaced population.

Many people within Peru felt that the government’s policies, which focused primarily on helping rich industrialists, ignored the specific problems caused by the earthquake….which, as you can expect, was highly unpopular.

Another economic problem was how the government was going to pay for disaster relief. One solution was to raise taxes, which they started hinting at, leading to pushback and forcing the government to drop the plan.

In addition to the short-term problems the government faced, there were many long-term ramifications from the Earthquake.

One long-term impact was the education levels of the generation that lived through the earthquake and their children. Even those who hadn’t been born yet when the earthquake hit completed less school on average when compared to their non-impacted counterparts. This trend can also be seen in health statistics and marriage rates.

A more positive long-term impact was in the formation of a new government agency.

After the Ancash Earthquake, the National Institute for Civil Defense was established by the Peruvian Government as a direct result of the earthquake to help reduce the impact of natural disasters in areas with seismic activity.

The system works by using a risk management approach. The implementation of this program within Peru helped the country prevent further disasters of this magnitude from happening again.

The Ancash Earthquake remains one of the most devastating in history. It killed tens of thousands of people, destroyed large amounts of property, and exposed the ineffectiveness of the Peruvian military government.

As with so many earthquakes, its deadliness didn’t come from the quake itself, but rather the damage done to buildings and the massive avalanche that resulted from the collapse of a nearby glacier.