Stack (geology)

Common card · No. 236951

A stack or sea stack is a coastal geological landform consisting of a steep and often vertical column or columns of rock in the sea near a coast, formed by wave erosion. Stacks are formed over time by wind and water, processes of coastal geomorphology. Stacks form when a headland is progressively eroded by hydraulic action and abrasion. The force of the sea exploits structural weaknesses in the rock, such as joints, bedding planes, and faults, causing cracks to expand into caves and eventually collapse into free-standing pillars. Coastal stacks provide critical predator-free nesting sites for seabirds, and many are prominent destinations for rock climbing. Isolated, steep-sided oceanic islets typically of volcanic origin are also loosely referred to as "stacks" or "volcanic stacks".

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