Sea Stacks: The Monoliths of the Oregon Coast
From Cannon Beach’s famous Haystack Rock to the jagged spires scattered along the southern coast, these formations are some of the most iconic and photographed features in the state. Sea stacks are the result of a long, violent dance between rock, waves, wind, and time.
What Are Sea Stacks?
Sea stacks are steep, isolated columns of rock that stand offshore, separated from the mainland by erosion. They were once part of the coastal headlands, connected to the shore before the ocean slowly carved them away. What remains is the toughest rock left standing after centuries—sometimes thousands of years—of relentless wave action.
On the Oregon Coast, sea stacks vary in size and shape. Some are massive, like Haystack Rock, towering over the beach. Others are slender spires or jagged clusters that barely break the surface at high tide. Together, they give Oregon’s shoreline its wild, sculpted look.
Why the Oregon Coast Has So Many Sea Stacks
The Oregon Coast is especially rich in sea stacks because of its geology and exposure to powerful Pacific storms. Much of the coastline is made up of basalt and sedimentary rock formed by ancient volcanic activity and tectonic forces. While basalt is relatively hard, it’s often fractured, giving the ocean plenty of weak points to exploit.
Add to that the constant pounding of winter storms, heavy surf, and strong tides, and you have the perfect recipe for coastal erosion. Unlike sandy coastlines that shift and rebuild, Oregon’s rocky shorelines erode slowly but dramatically, creating features like arches, caves, and eventually, sea stacks.
How Sea Stacks Form: Step by Step
The formation of a sea stack is a slow process that unfolds over many stages:
1. Cracks and Weaknesses Form
Waves exploit natural fractures, joints, and softer layers in coastal headlands. Saltwater seeps in, wind forces air into cracks, and temperature changes cause expansion and contraction.
2. Sea Caves Develop
Over time, these weaknesses widen into sea caves as waves repeatedly hammer the rock. On stormy days, wave pressure can be immense, forcing water and air deep into the rock face.
3. Arches Take Shape
As erosion continues, caves on opposite sides of a headland may meet, forming a sea arch. These arches are common sights along the Oregon Coast, especially near headlands and capes.
4. Collapse Creates a Sea Stack
Eventually, the arch becomes unstable and collapses under its own weight, leaving behind an isolated column of rock—the sea stack.
5. The Cycle Continues
Even sea stacks continue to erode. Over long periods, they may shrink, topple, or become low stumps called sea stumps, visible only at low tide.
Famous Sea Stacks on the Oregon Coast
The Oregon Coast is dotted with well-known sea stacks, each with its own character:
- Haystack Rock (Cannon Beach): One of the tallest sea stacks in the world, rising 235 feet above the sand. It’s also a protected marine garden and bird nesting site.
- Three Arch Rocks (near Oceanside): A dramatic cluster of sea stacks that serve as critical habitat for seabirds and marine mammals.
- Face Rock (Bandon): A striking formation with strong ties to local Native American legends.
- Needles and Spires (Samuel H. Boardman Scenic Corridor): In the south, razor-sharp stacks and cliffs create some of the most dramatic coastal scenery in the state.
Living Landmarks
Sea stacks aren’t just geological features—they’re ecosystems. Their sheer sides and isolated locations make them ideal nesting sites for seabirds like puffins, murres, and cormorants. At their bases, tide pools teem with sea stars, anemones, and crabs, especially during low tide.
Because they’re so important ecologically, many Oregon sea stacks are protected. Visitors are encouraged to admire them from a distance, especially during nesting seasons.
A Coast Shaped by Time
Each one represents thousands of years of erosion, collapse, and survival. They are reminders that the Oregon Coast is still very much alive—still changing, still being shaped by the ocean.
