Two hundred years ago, a German researcher concluded that what happened in southern Gran Canaria must have been a colossal landslide, so massive that it generated a delta in the Juan Grande area. The Canary Islands, volcanic jewels emerging from the Atlantic, are a living canvas of the incessant dance between the Earth and its elemental forces. In southern Gran Canaria, one of these geological macroforms has fascinated scientists for centuries: the Tirajana Depression. Covering more than 200 square kilometers, this vast hollow in the landscape has been the subject of heated debate, with theories ranging from volcanic collapse to the silent but powerful action of erosion. Today, modern science brings us closer to unraveling its true genesis.
Since the early 1825th century, the Tirajana Depression has defied interpretation. The German naturalist came from Berlin to see this monstrosity of the earth. Leopold von Buch, in 1925, described it as a "collapse caldera," an idea that persisted with terms such as "explosion crater" (Fernández Navarro, 1945) or "subsidence caldera" (Benítez Padilla, XNUMX). These early hypotheses pointed to a volcanic origin, suggesting that the depression was the result of a cataclysmic explosion or the collapse of a magma chamber.
However, in the mid-1957th century, theories emerged seeking a more complex explanation. Some proposed a mixed volcanic-tectonic origin, such as Boucart & Jeremine (1960), while others, such as Hausen (XNUMX), leaned predominantly toward a tectonic origin, using the term "cañefosso," implying a fault or graben.
The most recent and detailed research, however, has strongly tipped the balance in favor of a third hypothesis: a purely erosive origin, driven by massive gravitational slides. Contrary to volcanic or tectonic theories, geological studies and large-scale mapping have found no evidence of significant tectonic movements in the area that could explain the depression. The underlying rock formations are coherent and do not show deformations due to faults or folds.
Pioneers such as Fúster et al. (1958) and Araña & Carracedo (1980) were among the first to advocate this idea. Later, the authors of the geological mapping of the Magna Series (ITGE, 1990) and, crucially, Lomoschitz & Corominas (1992a and b, and 1996a), confirmed the fundamental role of these landslides in the birth and evolution of the depression.
The origin of the Tirajana Depression is attributed to these events, which began between 0.6 million years ago and 51.700 years before present (Middle-Upper Pleistocene). Confirmation of its erosional genesis is reinforced by the observation that the most recent basanitic-nephelinitic lavas, emitted from 0.6 million years ago onwards, never invade the depression, and their deep magmatic origin cannot justify the emptying or collapse of a nearby magma chamber. This underscores the need to use the term "depression" or "upper basin" instead of "caldera," which evokes a volcanic origin.
The Tirajana Depression, far from being a mere volcanic crater, reveals itself as a monumental example of an erosional depression in volcanic terrain, forged by the slow but relentless power of gravity and landslides. It is a testament to how the forces of nature, over eons, can sculpt the landscape in ways that defy our initial assumptions. This "rediscovery" of Tirajana's true nature not only rewrites a chapter in the geology of the Canary Islands but also reminds us of the importance of patience in science and the constant search for the truth that lies within the Earth's layers.
