Crumbling Cliffs: How Coasts Are Shaped by Erosion

Every year, parts of the Holderness Coast in East Yorkshire, UK, lose up to two metres of land — permanently swallowed by the sea. Since Roman times, more than thirty villages have vanished into the water there. That is one of the fastest rates of coastal erosion on Earth. Think about what that means: a road, a house, a field — gone within a lifetime. How does the sea have the power to destroy solid land? You probably already know that waves are involved, but the real story is much more detailed than 'waves hit the cliff and it falls down'.

Coastal erosion is the gradual wearing away of land by the sea. It happens through four main processes that often work together. **Hydraulic action** is the sheer force of waves crashing into a cliff face. As a wave hits, it traps air in cracks in the rock. The compressed air expands violently when the wave retreats, widening the cracks over time. No tools needed — just pressure. **Abrasion** (also called corrasion) is like sandpaper on a massive scale. Waves pick up pebbles, sand, and rock fragments, then hurl them against the cliff. These particles grind and scrape the rock face, slowly wearing it away. **Attrition** happens to the eroded material itself. Rocks and pebbles carried by the sea knock against each other repeatedly, breaking into smaller, smoother, and more rounded pieces. This is why beach pebbles feel smooth rather than jagged. **Solution** (or corrosion) occurs when seawater dissolves certain types of rock, especially limestone and chalk. The slightly acidic seawater reacts chemically with the rock, removing material without any physical impact. **How erosion builds coastal landforms** Waves focus their energy on weaknesses in a cliff — joints, faults, or softer rock layers. Hydraulic action and abrasion carve a notch at the base of the cliff called a **wave-cut notch**. The overhanging rock above becomes unstable and collapses. Over thousands of years, the cliff retreats inland, leaving behind a flat, gently sloping surface called a **wave-cut platform** that is visible at low tide. Where the coast juts out into the sea as a **headland**, erosion attacks both sides. Caves form on opposite sides; eventually they meet and break through to create an **arch**. When the roof of the arch collapses under its own weight, a tall column of rock is left isolated in the sea — a **stack**. Continued erosion at the base of the stack causes it to topple, leaving only a low, flat **stump**. **Factors that affect the rate of erosion** Not all coasts erode at the same speed. Two key factors control the rate: 1. **Rock type (lithology):** Hard rocks like granite resist erosion and erode slowly. Soft rocks like clay or boulder clay (such as on the Holderness Coast) erode very quickly. 2. **Wave energy:** Coasts exposed to long stretches of open ocean receive more powerful waves with greater energy. The Holderness Coast faces the North Sea with little to block incoming waves, increasing erosion rates. Sheltered coastlines in bays experience gentler waves and erode more slowly.