An aerial view of Lanzarote’s volcanic landscape and ocean
Volcanic island groups like the Azores in Portugal and the Canary Islands in Spain have been shaped by a lifetime of both submarine and subaerial (on land) volcanic activity.
It begins below the ocean. As eruptions add more rock and material to the growing piles we call volcanoes, islands eventually emerge.
Lush green caldera landscapes in the Azores, Portugal with serene lakes and rolling hills. Photo: Erwan Grey, pexels.com
At the same time, erosion and collapse work against that growth. Wave action wears away landforms below the ocean and along coastlines, while mass-wasting events, from small rockfalls to massive flank collapses, reshape them through gravity and time. These are dynamic environments, and the landscapes that attract residents and visitors alike are constantly changing.
Janine Krippner
Like any environment, we need to understand the land we live on so we can do so safely and work with natural processes in ways that reduce or eliminate harm.
What happens on the seafloor around volcanic islands also impacts communities. I have previously covered how submarine eruptions can produce earthquakes as well as deadly pyroclastic surges that can travel over water and onto the land.
Most of a volcanic island’s structure lies beneath the ocean. By studying marine cores, scientists build a picture of the processes occurring below the waves. A pipe or drill is pushed into the seafloor and brings back a column containing layers of sediment, rock, and anything else in that location.
Scientists use different techniques to determine the ages of those layers. These include radiocarbon dating tiny shells or the remains of microscopic organisms called foraminifera, studying pollen, or dating volcanic glass. Different methods are appropriate for different age ranges. For example, radiocarbon dating is generally only useful for material younger than about 60,000 years.
Using these records, researchers can identify layers deposited by volcanic ash, pyroclastic flows, landslides, and turbidity currents that some landslides can transform into. Thin ash layers or scattered grains of volcanic glass can also point to large explosive eruptions that occurred far away. Some of these processes can generate tsunamis that threaten nearby islands and can damage critical seafloor infrastructure such as internet cables.
aerial view of La Graciosa Island with vibrant blue skies and fluffy clouds. Photo: Marian Florinel Condruz, pexels.com
Lava flows reaching the ocean can build lava deltas. These deposits can become thick and steep, creating potential for collapse and offshore landslides. Deposits can take decades, or even longer to become unstable enough to fail.
Each piece of information is part of a puzzle and reveals more of an ever-evolving picture. Where possible, the submarine record can be linked to processes observed on land. Understanding these systems requires many research projects, involving different specialties and often spanning decades.
Scientists can also identify patterns through time. In some volcanic regions, periods of increased activity have been linked to times of sea-level change, which can alter the pressures acting on the Earth’s crust.
In the end, all of this fascinating work benefits those living in these environments and those who travel to experience them. The better we understand these systems, the better equipped communities, institutions, and governments are to make informed decisions about the future.
An aerial view of Lanzarote’s volcanic landscape and ocean under a cloudy sky in the Canary Islands. Photo: Marian Florinel Condruz, pexels.com
