Why some coffee is grown dangerously close to volcanoes

What about volcanoes

There are more than 800 million people in the world, nearly 10% of the world's population lives within 100 kilometres of the world's 1,431 active volcanoes.

While volcanoes can have enormous destructive power, they also attract millions of tourists each year and provide geothermal energy that can be harnessed by local communities.

In addition, volcanic material produced during eruptions can mix with the surrounding soil to produce the most fertile soils for growing crops.

Growing coffee in volcanic areas

The coffee plant in particular thrives in volcanic soil, which is characterised by a large number of physical, chemical and mineral properties that make it agriculturally superior to other soil types.

However, soilis only one part of the story. Volcanic environments also provide the conditions for growing the world's most delicious coffee.

The coffee plant in volcanic areas

The coffee plant needs various nutrients to grow, which are supplied by the soil.

Volcanic soils are fertile because they are relatively 'young'. They retain many of the nutrients that were present in the original rock. Although they vary from volcano to volcano.

Andisols commonly contain phosphorus, potassium, calcium, magnesium, zinc, iron, and boron, which are important for coffee tree development.

For example, potassium levels affect the formation of coffee cherries, but also sugar levels and citric acid content, which alter the taste of coffee.

Calcium is important for root and leaf development and affects how quickly the fruit ripens, while boron increases the yield of the crop.

Andisols - the power of volcanic soil

Most volcanic soils are 'tephra'. Tephra is a mixture of volcanic particles (ash) and rock fragments that are expelled from the volcano during an eruption and then fall to the ground.

Over time, the tephra breaks down to form what we call volcanic soil - also known as Andisols or Andosols.

Andisols are light and fluffy. They contain high proportions of silicate glass and tend to accumulate organic matter.

Types of eruption

The abundance of volcanic soil, and the growth of coffee trees in that soil, depends on the chemistry, nature and frequency of volcanic eruptions.

Eruptions can be divided into two types: effusive eruptions and explosive eruptions.

Effusive eruptions

Primarily characterized by outpourings of lava that produces iron- and magnesium-rich andisols.

Explosive eruptions

Are characterized by the ejection of volcanic ash that are rich in silica (called tephra).

The ground then begins to produce andisols that are high in aluminium, sodium and potassium.

Most volcanic soils discovered around the world are formed by explosive eruptions. Andisols form less frequently after effusive eruptions because the surfaces formed by lava flows can take up to thousands of years to break down into soil.

The silent ring of fire

Many Latin American coffee-producing countries, including Colombia, Ecuador and Guatemala, are located around what is known as the "Silent Ring of Fire," which contains more than 75% of the world's active and dormant volcanoes.

These countries contain many explosively erupting volcanoes that produce Andisols.

Because most of these volcanoes erupt at intervals of tens to hundreds of years, fresh tephra occasionally falls on the surrounding land. This protects the underlying Andisols from physical erosion and weathering.

It also means that fresh tephra appears periodically, providing a constant supply of nutrients to replenish the soil and maintain fertility levels.

Impact of volcanic soil on coffee

In addition to the nutrient-rich soils that volcanoes create, the soil offers other benefits for growing coffee. For example, the arabica plant thrives at altitudes of 1 000 to 2 000 m above sea level and between 18 and 21 °C.

Volcanoes are usually found along high altitude mountain belts, such as the volcanic arcs of Central and South America.

The quality of coffee generally increases with increasing altitude, where temperatures are cooler, bean growth is slower and cherries thus ripen more slowly.

The next time you drink a delicious cup of coffee from a volcanic region, think about the natural forces that helped create its unique flavor. And also think about the farmers who work in these dangerous volcanic areas every day to ensure the coffee tastes so perfect.