Since the Cumbre Vieja volcano on La Palma began to erupt on September 19, 2021 , most of the activity has taken place on the surface. For several weeks now, thick layers of lava have passed over farmland, roads and homes in the southwestern part of La Palma, in the Canary Islands.
In the midst of this volcanic activity, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite has managed to image a dense column of ash flowing south on October 4, 2021. According to the Advisory Center From Volcanic Ashes of Toulouse, the column reached 3 kilometers on October 4, posing a danger to aircraft in the area.
The eruption was not energetic enough to inject large amounts of ash and gases into the stratosphere, but it was to produce a growing plume of emissions that helped form this fabulous cloud pattern known as the mackerel sky. The clouds appear in a wavy shape because the gases and ash collide with a layer of drier and warmer air that acts as a barrier, making the clouds move horizontally in the sky and causing this curious wavy shape of concentric waves that we can see in the snapshot of the US space agency. (The process is similar to when we throw a stone in a pond).
It is called mackerel sky because the cloud formations are similar to the scales of this fish. Its scientific name is Stratocumulus undulatus.
