A chasm in the continental shelf
Off the northern coast of Spain, located beneath the waves of the Bay of Biscay, the seafloor drops away into a massive chasm known as the Santander Canyon. This submarine canyon is a colossal geological feature, in places plunging more than 3,000 meters from the continental shelf to the abyssal plain. For comparison, the Grand Canyon in Arizona has a maximum depth of about 1,857 meters. The Santander Canyon is a complex trench; it is a complex, branching system that carves deeply into the continental margin.
The canyon begins on the relatively shallow continental shelf and extends for hundreds of kilometers out into the deep ocean. Its V-shaped profile and steep, rocky walls are features carved by powerful erosional forces. Unlike canyons on land, which are primarily shaped by rivers, submarine canyons are sculpted by different, more enigmatic processes. The primary causes of the Santander Canyon are powerful, sediment-heavy underwater flows called turbidity currents. These events are essentially underwater avalanches.